A Comparative Study of
the Appendicular Musculature of
Penguins (Aves: Sphenisciformes)
DONALD O. SCHREIWEIS,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY ? NUMBER 341
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S M I T H S O N I A N C O N T R I B U T I O N S T O Z O O L O G Y ? N U M B E R 3 4 1
A Comparative Study of
the Appendicular Musculature of
Penguins (Aves: Sphenisciformes)
Donald 0. Schreiweis
SMITHSONIAN INSTITUTION PRESS
City of Washington
1982
A B S T R A C T
Schreiweis, Donald O. A Comparative Study of the Appendicular Muscu-
lature of Penguins (Aves: Sphenisciformes). Smithsonian Contributions to Zoology,
number 341, 46 pages, 19 figures, 1982.?The gross anatomy of all the
appendicular muscles is compared in 14 species, representing the 6 living
genera of Sphenisciformes. Particular emphasis is placed on the interrelation-
ships indicated by variations in the taxa. Eudyptes pachyrhynchus is used as a
type for which all the appendicular muscles are described and most are
illustrated. The salient features of other taxa, as they differ from the condition
found in E. pachyrhynchus, are given. Similarities and differences are compared
quantitatively in respect to 47 items in the wing and and 41 in the leg, using
the method of Hudson et al. (1966:9-11). The results are given in the form of
cumulative scores of differences and correlation coefficients.
The results of the comparison of the wing musculature support those for
the leg. The cumulative scores and correlation coefficients give closely parallel
results.
The Sphenisciformes constitute a rather uniform group of birds. The results
of this study support the present classification of the order, in which 14 species
are grouped into 6 genera. A tentative phylogeny of penguins is projected on
the basis of variations in the wing and leg muscles.
OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded
in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea
cavemosa (Linnaeus).
Library of Congress Cataloging in Publication Data
Schreiweis, Donald O.
A comparative study of the appendicular musculature of penguins (Aves: Sphenisciformes)
(Smithsonian contributions to zoology ; no. 341)
Bibliography: p.
Includes index.
Supt. of Doc. no.: SI 1.27:341
1. Penguins?Anatomy. 2. Wing?Muscles. 3. Leg?Muscles. 4. Anatomy, Comparative.
I. Title. II. Series.
QL1.S54 no. 341 [QL696.S473] 591s 81-607820 [598.4'41] AACR2
Contents
Page
Introduction 1
Materials and Methods 1
Acknowledgments 2
Muscles of the Pectoral Appendage 2
Muscles of the Pelvic Appendage 14
Position of the Flexor Tendons Passing the Intertarsal Joint 21
Discussion and Conclusions 25
Appendix: Interesting Features of the Appendicular Muscles 29
Literature Cited 31
Abbreviations on Illustrations 33
Figures 1-19 34
Index 45
m

A Comparative Study of
the Appendicular Musculature of
Penguins (Aves: Sphenisciformes)
Donald 0. Schreiweis
Introduction
Penguins are an ancient group of birds that
had become flightless and highly specialized for
underwater locomotion by the Eocene. Simpson
(1975:35) considered penguins related to Procel-
lariiformes, basing this relationship on the struc-
ture of the skull and mandible. In the oldest
known fossil penguins, the structure of the man-
dible, the shape of the foramen magnum, and the
arrangement of palatal bones are similar to the
procellariiform type. Sibley and Ahlquist (1972)
recently concluded that the egg-white protein
patterns of penguins were more like those of the
Procellariiformes than those of any other group,
although they also resembled several other groups
of aquatic birds. The descriptive myology of pen-
guins presented in this paper may help to resolve
the problem of phylogeny when comparable stud-
ies on other water birds become available.
Although the appendicular muscles have been
studied in a few sphenisciform birds by various
investigators, no one has made a concerted at-
tempt to work out in detail the similarities and
differences between the various genera and spe-
cies. Such differences and similarities may serve
as a basis for a study of functional morphology,
Donald 0. Schreiweis, Premedical Studies Program, Saint Louis
University, Saint Louis, Missouri 63103.
as well as a study of phylogenetic and systematic
relationships among these taxa.
A detailed study of all appendicular muscles,
using descriptive and numerical methods, was
made on a series of 28 specimens, representing 6
genera and 14 species. The pectoral musculature
is unlike that of any other group of birds. Most of
the muscles in the wing are reduced to tendons,
a condition not encountered in any other group,
while the leg muscles deviate less from the general
avian pattern. The more interesting features of
the appendicular muscles of penguins are sum-
marized in the appendix.
MATERIALS AND METHODS.?The classification
followed is that of Falla and Mougin (1979). I
dissected the following species: Aptcnodytes patagon-
icus (2); A.forsteri (2); Pygoscelis papua (2); P. adeliae
(3); P. antarctica (2); Eudyptes pachyrhynchus (2); E.
chrysocome (2); E. chrysolophus schlegeli (1); E. c.
chrysolophus (2); Megadyptes antipodes (1); Eudyptula
minor minor (1); E. m. albosignata (1); Spheniscus
demersus (2); S. humboldti (1); S. magellanicus (2); S.
mendiculus (2).
Fresh specimens were initially injected in all
parts with a 1:10 solution of formalin. After
several weeks, specimens were opened and washed
in tap water for 3 to 5 days to remove most of the
formalin. Subsequently, all were stored in 65%
ethyl alcohol.
To facilitate study of the musculature in most
1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
specimens, the coracoid was separated from the
clavicle proximally and from the sternum distally,
and the femur was disarticulated at the aceta-
bular joint. The extremities of the limb bones
were exposed by partially dissecting the joint
capsules without complete disarticulation. Each
muscle was exposed from origin to insertion by
cutting bellies or tendons of certain muscles at
prescribed points.
Descriptions of the origin, belly, and insertion
of each muscle are given for Eudyptes pachyrhynchus.
The positional (anatomical) axes utilized are
those related to the functional axes: for the wing,
the extended position of underwater flight; for
the leg, the normal standing position. The loca-
tion of muscle attachments (e.g., "at about 0.63
tibiotarsus") were obtained by measuring the
point of attachment from the proximal end of the
bone holding the calipers parallel to the long axis
of the bone. These measurements were then di-
vided by the length of the bone.
Following each description, a comparison of
the muscle is given for other species as these differ
from E. pachyrhynchus. Included in the comparison
are remarks concerning observations made by
other workers. In many instances, observations
made in this study clarify those of earlier workers.
Numerical comparisons were made using the
method of Hudson et al. (1966:9-11). Tables of
quantitative data are available from the author
on request. Anatomical nomenclature follows
that of the Nomina Anatomica Avium (Baumel et al.,
1979).
ACKNOWLEDGMENTS.?I wish to express my ap-
preciation and thanks to Dr. George E. Hudson
under whose guidance and direction this study
was completed. He made available many of the
specimens and, through him, various specimens
were loaned from other institutions. I also wish to
thank Drs. Herbert L. Eastlick, C. M. McNeil,
and Richard A. Parker of Washington State Uni-
versity, who critically read the manuscript and
offered suggestions.
Specimens examined for this study are part of
an extensive alcoholic collection at Washington
State University, representing all living orders of
birds. Dr. Richard L. Zusi of the National Mu-
seum of Natural History, Smithsonian Institu-
tion, loaned 12 specimens. Dr. Dean Amadon of
the American Museum of Natural History loaned
one specimen each of Eudyptes pachyrhynchus and
Spheniscus humboldti. Mr. Warwich M. Howe of the
New Zealand Department of Internal Affairs sup-
plied one specimen each of Eudyptes pachyrhynchus,
Megadyptes antipodes, and Eudyptula minor albosig-
nata. Mr. T. H. Barry of the South African Mu-
seum supplied a specimen of Spheniscus demersus.
This study was supported in part by a grant-
in-aid (GB-6088) from the National Science
Foundation.
Muscles of the Pectoral Appendage
M . LATISSIMUS DORSI
The latissimus dorsi consists of three distinct
parts: latissimus dorsi cranialis, latissimus dorsi
caudalis, and latissimus dorsi metapatagialis.
Latissimus dorsi cranialis
(LAT. DOR. CRAN.)
FIGURES 1, 2, 8
DESCRIPTION.?This large flat muscle (Figure
1) arises from the dorsal spines of about the last
cervical and first five thoracic vertebrae. The
origin is aponeurotic. Fleshy fibers of this muscle
converge as they pass forward and outward, and
terminate on a long, narrow tendon. The tendon
is about one-fourth the length of the humerus. It
passes through a fibrous pulley (Figure 8) much
like a thread passes through the eye of a needle.
This pulley, unique to the Spheniscidae, is at-
tached to the axillary border of the scapula just
behind the glenoid fossa. Insertion is on the pos-
terior border of the humeral shaft, near the distal
border of the pneumatic fossa.
COMPARISON.?An accessory slip from the cra-
nial edge of the latissimus dorsi cranialis occurs
in Aptenodytes and Pygoscelis. This accessory slip
NUMBER 341
inserts on the dorsal surface of the dorsal head of
the triceps scapularis.
and Eudyptula and intermediate in Eudyptes, Sphen-
iscus, and Megadyptes.
Latissimus dorsi caudalis
(LAT. DOR. CAUD.)
FIGURES 1, 2, 8
DESCRIPTION.?The latissimus dorsi caudalis
(Figure 2) is distinct and separated by a wide
interval from the latissimus dorsi cranialis. It
arises by means of a delicate aponeurosis from the
inferior edge of the ilium and the abdominal
muscles immediately posterior to the last thoracic
rib. Fleshy fibers on the band-like belly pass
forward toward the shoulder and terminate on a
long tendon which, after passing through the
fibrous pulley mentioned above, is inserted on the
posterior border of the humeral shaft adjacent to
the insertion of the latissimus dorsi cranialis. The
tendons of the latissimus dorsi cranialis and latis-
simus dorsi caudalis are partly fused.
COMPARISON.?The latissimus dorsi cranialis
and latissimus dorsi caudalis are fused along their
contiguous borders in Aptenodytes and Pygoscelis.
All other genera have these two parts widely
separated.
Latissimus dorsi metapatagialis
(LAT. DOR. MET.)
FIGURE 1
DESCRIPTION.?This muscle is quadrilateral in
form. It arises by a narrow aponeurosis from the
dorsal spines of thoracic vertebrae 4, 5, and 6.
Insertion is along a broad line on the skin of the
lateral line of the trunk. The belly of the latissi-
mus dorsi metapatagialis is much wider than that
of the latissimus dorsi caudalis and nearly as wide
as the belly of the latissimus dorsi cranialis.
COMPARISON.?The latissimus dorsi metapata-
gialis exhibits a wide range of development in
penguins. In Aptenodytes this muscle is very wide
(1.01 scapula), reaching from the base of the neck
to the lumbar region. It is narrowest in Pygoscelis
M . RHOMBOIDEUS SUPERFICIALIS
(RHOM. SUP.)
FIGURES 1, 2, 7
DESCRIPTION.?This wide, flat muscle (Figure
2) arises by means of a narrow aponeurosis from
the dorsal spines of the last one or two cervical
vertebrae and the first three or four thoracic
vertebrae. The fibers pass transversely and
slightly forwards; they are inserted on about the
anterior half of the vertebral border of the scapula
and the scapular process of the clavicle.
COMPARISON.?This muscle is very similar in
all species. In Eudyptes chrysocome, Watson (1883:
76) found this muscle arising from the dorsal
spines of the three anterior thoracic vertebrae and
the last two cervical vertebrae. In this penguin,
as well as in Pygosceles taeniatus ( = Pygoscelis papua)
and Spheniscus minor (= Eudyptula minor), he found
the insertion to be confined to the cranial two-
thirds of the vertebral border of the scapula. The
insertion is not this extensive in any of the pen-
guins studied. Gervais and Alix (1877:444) found
the rhomboideus superficialis in Eudyptes chrysolo-
phus attached to the dorsal spines of the last two
cervical vertebrae, as well as to the dorsal spines
of thoracic vertebrae 1 through 5. Such a wide
origin was not present in any specimen of penguin
studied.
M . RHOMBOIDEUS PROFUNDUS
(RHOM. PRO.)
FIGURES 2, 3, 7
DESCRIPTION.?The rhomboideus profundus
(Figure 3) arises from the dorsal spines of about
five or six thoracic vertebrae (thoracic vertebrae
2-7) by means of an aponeurosis. Fleshy fibers
pass transversely and somewhat obliquely back-
wards to a fleshy insertion on about the caudal
three-fourths of the vertebral border of the scap-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
ula. Rhomboideus superficialis covers about the
cranial two-thirds of the rhomboideus profundus.
M . SERRATUS PROFUNDUS
(SERR. PRO.)
FIGURE 7
DESCRIPTION.?The serratus profundus consists
of four large, flat fleshy fascicles superimposed on
one another. These fascicles arise from the last
two cervical and first two thoracic ribs, dorsal to
the uncinate processes. The fascicles pass postero-
dorsally and insert on about the caudal half of
the costal surface of the scapula near the vertebral
border.
COMPARISON.?The small cranial fascicle is usu-
ally absent in Spheniscus and Megadyptes. Apteno-
dytes, Pygoscelis, Eudyptes, and Eudyptula generally
possess four fascicles. The caudal fascicle is some-
times absent. Watson (1883:79) reports four mus-
cular plates in Eudyptes chrysocome and P. papua,
which arise from the second, third, fourth, and
fifth ribs. In Aptenodytes patagonicus and Eudyptula
minor he found only three digitations, the first
from the second rib, the second from the third
and fourth ribs, and the third from the fifth rib.
In no instance was the origin from the third,
fourth, and fifth ribs in any penguin examined in
this study. Schoepss (1829:97) has the serratus
profundus arising from the transverse processes of
the first and second dorsal vertebrae, as well as
from the caudal border of the second rib. Gervais
and Alix (1877:443) found five fleshy slips in
Eudyptes chrysolophus of which the most cranial
arises from the transverse process of the last cer-
vical vertebra, the second from the first rib be-
neath the transverse process, and the other three
from the following ribs dorsal to the uncinate
processes. None of the specimens in this study had
five slips, nor has any other worker reported this
many muscular slips for the serratus profundus.
M . SERRATUS SUPERFICIALIS CRANIALIS
(SERR. SUP. CRAN.)
FIGURE 7
DESCRIPTION.?This muscle arises by means of
two fleshy fascicles from the last cervical and first
thoracic ribs. The fascicles fuse near the origin.
The fibers pass obliquely anterior and dorsal.
Insertion is mostly fleshy on the axillary border
of the scapula. The insertion partially separates
the origin of the subscapularis caput laterale from
that of the subscapularis caput mediale.
COMPARISON.?My observations agree with
those of Schoepss (1829:96), who found this mus-
cle in S. demersus attached to the outer surfaces of
the last cervical rib and to the lower part of the
first true rib. Gervais and Alix (1877:443) describe
this muscle as arising from the third and fourth
ribs in E. chrysolophus. Watson (1883:78) gives the
origin as the second, third, and fourth vertebral
ribs. In one specimen of Pygoscelis antarctica, I
found the origin to be from the last cervical and
first two thoracic ribs.
M . SERRATUS SUPERFICIALIS CAUDALIS
(SERR. SUP. CAUD.)
FIGURES 3, 7
DESCRIPTION.?This muscle (Figure 7) has three
fascicles arising from thoracic ribs 2, 3, and 4, a
little below the uncinate processes. The fibers pass
nearly at a right angle to the long axis of the
scapula. Insertion is mostly fleshy on the ventro-
lateral border of about the posterior fifth of the
scapula.
COMPARISON.?The origin of this muscle is gen-
erally from the second, third, and fourth thoracic
ribs. Variations to this pattern occur. One speci-
men of A. patagonicus has only two fascicles, which
arise from the third and fourth thoracic ribs. This
pattern is also present in one specimen of Pygoscelis
adeliae. The posterior fascicle in one specimen of
P. antarctica arises from both the fourth and fifth
thoracic ribs. Megadyptes has only two fascicles,
NUMBER 341
which arise from the second and third thoracic
ribs. Watson (1883:78) found this muscle arising
by two digitations from the fourth and fifth ribs
in P. papua. Schoepss (1829:94) reports this muscle
arising from four ribs in penguins. Watson (1883:
78) never found the serratus superficialis caudalis
arising from more than three ribs, and I found it
arising from three ribs in all except one specimen
in which the posterior slip arose from both the
fourth and fifth ribs.
M . SCAPULOHUMERALIS CAUDALIS
(SCAP. HUM. CAUD.)
FIGURES 1-3, 5-7
DESCRIPTION.?The scapulohumeralis caudalis
(Figure 3) has an extensive origin from about the
posterior two-thirds of the dorsal and lateral sur-
faces of the scapula. The fibers pass obliquely
forward and end on a strong tendon, which is
inserted on the posterior border of the humerus
(0.33 humerus).
COMPARISON.?The scapulohumeralis caudalis
is a very uniform muscle in the Spheniscidae. The
cranial end of the origin shows only slight varia-
tion between genera of penguins, ranging from
0.33 scapula in Aptenodytes to 0.44 scapula in
Eudyptula.
of the sternum, the interosseus membrane be-
tween this process and the corpus sterni, a line
along the entire length of the sternal keel ventral
to the origin of the supracoracoideus, the lateral
surface of the clavicle below the shoulder joint,
the cranioventral edge of the membrana sterno-
coraco-clavicularis, and the aponeurosis covering
the supracoracoideus. The belly is composed of
three distinct parts. Fibers of the clavicular part
pass caudolaterally. Those of the caudolateral
part pass craniolaterally, while those of the large
middle part pass obliquely at increasing angles
from the sternum. The clavicular fibers end on a
specialized part of the tendon of insertion, which
ends on about the proximal fifth of the cranial
border of the humeral shaft, joining the tendon
of the propatagialis near the proximal end of the
humerus. The remaining fibers insert by means
of a wide, curving tendon on the proximal third
of the cranioventral edge of the humerus.
COMPARISON.?The pectoralis thoracica shows
no significant variations in the Spheniscidae.
Reid (1835:140) described the muscle in Apteno-
dytes patagonicus as arising from "the cartilages of
the ribs, and from the anterior part of the cora-
coid bone" in addition to the origin given above.
Such is not the case in any of the penguins
examined in this study or in the study by Watson
(1883:81).
M . PECTORALIS
This muscle consists of three slips: pectoralis
thoracica, pectoralis propatagialis (which is not
present in penguins), and pectoralis pars subcu-
tanea abdominalis.
Pectoralis thoracica
(PECT. THO.)
FIGURES 2-7
DESCRIPTION.?The pectoralis thoracica (Fig-
ure 4) is a very powerful muscle which arises from
the lateral edge of the sternum posterior to the
coracobrachialis caudalis, the trabecula lateralis
Pectoralis pars subcutanea abdominalis
(PECT. SUB. ABD.)
FIGURE 4
DESCRIPTION.?Pars subcutanea abdominalis is
a wide, flat, ribbon-like muscle that arises from
the skin along the flank. The caudal end of the
origin is opposite the region of the acetabulum.
The muscle passes cranially and somewhat dor-
sally to insert on the dorsal border of the pecto-
ralis thoracica caudal to the insertion of the latter
on the humerus.
COMPARISON.?The maximum width of this
muscle relative to the humeral length shows some
variation between genera of penguins. It is nar-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
rowest in Aptenodytes and Eudyptes, and interme-
diate in Megadyptes, Spheniscus, and Pygoscelis. Wat-
son (1883:81) describes the pectoralis pars sub-
cutanea abdominalis as inserting on the anterior
margin of the humerus. This is not the case in
any species of penguin examined in this study.
M . SUPRACORACOIDEUS
(SUP. COR.)
FIGURES 1-3, 5
DESCRIPTION.?The supracoracoideus (Figure
5) arises from the entire surface of the sternum
not occupied by the pectoralis thoracica, from the
proximal part of the trabecula lateralis of the
sternum, from the keel of the sternum, and from
the basal end of the coracoid. It also has a consid-
erable attachment to the membrana sterno-cor-
aco-clavicularis. From these origins the fibers con-
verge to a stout, flattened tendon which, after
passing through the canalis triosseus, inserts (Fig-
ures 1-3) on an oblique ridge on the proximodor-
sal part of the humerus between the insertions of
the deltoideus major and deltoideus minor. The
supracoracoideus is very well developed in com-
parison to the pectoralis thoracica, a fact noted
by every anatomist who has worked on any mem-
ber of the group.
COMPARISON.?The small, separate anterior
part of the supracoracoideus described by
Schoepss (1829:124), Gervais and Alix (1877:
447), and Watson (1883:82) is the long head of
the deltoideus minor and will be described later
with that muscle. The supracoracoideus is a very
strong, bipennate muscle in penguins and is very
similar in all.
M . CORACOBRACHIALIS CRANIALIS
(COR. BRA. CRAN.)
FIGURES 5, 6
DESCRIPTION.?This muscle (Figure 5) is small
and embedded in a very dense investment of
fascia. It arises from the cranioventral surface of
the distal apex of the coracoid. The belly is very
weak. Insertion is tendinous on the extreme prox-
imal end of the cranioventral humeral shaft and
is covered by the pectoralis thoracica.
COMPARISON.?The coracobrachialis cranialis is
present in all species of penguins studied and
shows the same relative degree of development.
It is not described in the major treatises on pen-
guin myology.
M . CORACOBRACHIALIS CAUDALIS
(COR. BRA. CAUD.)
FIGURES 3, 5-7
DESCRIPTION.?The coracobrachialis caudalis
has a fleshy origin from a short, narrow line along
the cranial third of the craniolateral edge of the
corpus sterni and from about the proximal third
of the lateral surface of the coracoid (Figure 6).
The belly is large and tapered to a point at each
end. Insertion is by a strong tendon on the dorsal
surface of the internal tuberosity of the humerus
(Figure 3).
COMPARISON.?This muscle shows remarkable
uniformity in penguins.
M . STERNOCORACOIDEUS
(STER. COR.)
FIGURE 7
DESCRIPTION.?This muscle has a fleshy origin
from the craniolateral sternal spine and the cra-
nial border of the sternum. The sternocoracoideus
is a strong, triangular muscle. Insertion is fleshy
on a large triangular area of the proximal end of
the dorsal surface of the coracoid.
COMPARISON.?A very uniform muscle among
penguins but of varying length. It is longest in
Pygoscelis and shortest in Spheniscus. The remain-
ing genera are of intermediate length. This mus-
cle is not described by Watson (1883).
NUMBER 341
M . SUBCORACOIDEUS
(SUBCOR.)
FIGURE 7
DESCRIPTION.?The subcoracoideus is a large,
powerful muscle arising fleshy from the dorsal
surface of the caudal end of the spina externa of
the sternum and partly tendinous from the adja-
cent cranial edge of the corpus sterni. As it passes
toward the shoulder, it is further attached to the
dorsomedial surface of the coracoid and adjacent
membrana sterno-coraco-clavicularis. Near the
shoulder joint the subcoracoideus fuses with the
subscapularis. Insertion is by a common, short
but strong, tendon at the proximal end of the
bicipital crest of the humerus. The tendon is
strongly attached to the adjacent joint capsule.
COMPARISON.?The subcoracoideus is very sim-
ilar in all penguins.
M . SUBSCAPULARIS
(SUBSCP.)
FIGURES 2, 3, 5-7
DESCRIPTION.?The subscapularis is divided
into two heads, which are partially separated by
the serratus superficialis cranialis (Figure 7). The
subscapularis caput mediale (SUBSCP. (CAP. MED.))
arises fleshy from about the proximal third of the
costal surface of the scapula, from a very small
area on the medial surface of the scapular process
of the clavicle, and a small cranial part from the
medial surface of the coracoid distal to the sub-
coracoideus. Hudson et al. (1969:464) refer to
that part of the subscapularis arising from the
coracoid, clavicle, and adjacent scapula as a cra-
nial head of the subcoracoideus. Only the slightest
indication of a division of this muscle mass exists
in penguins. Because of the very intimate associ-
ation with the caput mediale, I have chosen to
consider it a part of the latter. The fibers of the
caput mediale almost at once unite with those of
the subcoracoideus and subscapularis caput lat-
erale (SUBSCP. (CAP LAT.)). The caput laterale
(Figure 3) arises fleshy from about the cranial
two-fifths of the lateral surface of the scapula.
Insertion of the subscapularis is by means of a
tendon common to it and the subcoracoideus.
This tendon inserts on the proximal end of the
bicipital crest of the humerus. The caput mediale
is smaller than the caput laterale.
COMPARISON.?The caput mediale reaches far-
thest distally on the scapula in Megadyptes and is
shortest in Pygoscelis; the remaining genera are
intermediate. Gervais and Alix (1877:445) state
that the caput laterale {petit rond) inserts above
the caput mediale (sous-scapulaire). Every speci-
men in this study and those studied by Watson
(1883:85) have the caput laterale and caput me-
diale inserted by means of a common tendon.
M . PROPATAGIALIS
(PROPAT.)
FIGURES 1-4
DESCRIPTION.?The propatagialis (Figure I)
arises fleshy from the dorsal apex of the coracoid,
the craniolateral edge of the clavicle, and the
intervening coracoclavicular ligament. Its belly is
stout and partly separable into two layers. Inser-
tion is by means of a very heavy tendon along
nearly the entire length of the cranial edge of the
humerus. The tendon continues along the cranial
border of the ventral surface of the radius and
contributes to the formation of the alar aponeu-
rosis. Beyond the wrist, the tendon becomes pro-
gressively less distinct.
COMPARISON.?The propatagialis exhibits little
variation among penguins. No indication of a
division into superficial and deep layers is present
in Eudyptula, P. antarctica, P. adeliae, and one spec-
imen of E. pachyrhynchus. Watson (1883:88) de-
scribes a deep and superficial part to this muscle.
The superficial part {deltoides posterieur of Gervais
and Alix) corresponds to the deltoideus major in
Watson's opinion. Schoepss (1829:82, 86) figures
a cranial and a caudal belly for the tensor patagii
longus of penguins. The caudal belly of his de-
scription most definitely corresponds to the del-
8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
toideus major. Meckel (1828:337-343) also de-
scribes two bellies for the tensor longus, one of
which can with difficulty be separated from the
pectoralis major. These obviously correspond to
the two partial layers described above for E.
pachyrhynchus. Watson describes an accessory slip
to the tensor patagii. This slip corresponds to the
long head of the deltoideus minor.
M . DELTOIDEUS MAJOR
(DELT. MAJ.)
FIGURES 1, 2
DESCRIPTION.?The deltoideus major (Figure 2)
is a very thin, triangular muscle. It arises fleshy
from the distal apex of the clavicle, the dorsal
surface of the coracoscapular ligament, and the
acromial process of the scapula. The fibers con-
verge distally onto a short tendon, which inserts
on the caudodorsal edge of the humerus very
close to the insertion of the latissimus dorsi.
COMPARISON.?The belly is triangular in most
genera. It is strap-like in Spheniscus. The belly is
shortest in Aptenodytes and Megadyptes, and longest
in Eudyptes; intermediate in the remaining genera.
The tendon is shortest in Eudyptes and Spheniscus
and is longest in Megadyptes and Pygoscelis. Apteno-
dytes and Eudyptula are intermediate. Descriptions
by other workers are very confused.
M . DELTOIDEUS MINOR
(DELT. MIN.)
FIGURES 2, 3, 6
DESCRIPTION.?This muscle has two distinct
heads in the Spheniscidae. The short dorsal head
(Figure 3) arises fleshy from the acromial process
of the scapula and from the coraco-scapular lig-
ament. The short head fuses with the long head
almost from the origin of the former. The long
ventral head (Figure 6) arises from the caudal
third of the membrana sterno-coraco-calvicularis,
from the cranial edge of the manubrial spine, and
from a long, narrow line along most of the ven-
tromedial edge of the coracoid. The fibers con-
verge on a short, strong tendon, which inserts in
common with the short head on the external
tuberosity of the humerus deep to the propatagi-
alis.
COMPARISON.?In most penguins the origin also
arises from the clavicular process of the coracoid
inside the canalis triosseum. Eudyptula and most
Eudyptes lack this part of the origin.
M . TRICEPS BRACHII
DESCRIPTION.?The triceps brachii consists of
two distinct parts, a triceps scapularis from the
scapula and clavicle and a triceps humeralis from
the caudal surface of the humerus.
Triceps scapularis
(TRI. SCAP.)
FIGURES 1-3
The triceps scapularis is very large and com-
posed of a dorsal and ventral head. The much
larger dorsal head (Figure 1) arises fleshy from
the acromial process of the scapula, the adjacent
joint capsule, and a long, narrow line on the
medial and dorsal surfaces of the clavicle dorsal
to the origin of the propatagialis. This head is
partially divided into a superficial and deep layer.
At about 0.35 humerus the dorsal head ends on
a strong tendon common to it and the ventral
head. The smaller ventral head (Figure 2) arises
fleshy from the axillary border of the scapula
immediately behind the glenoid fossa. This belly
is firmly attached to the fibrous loop through
which the tendons of the latissimus dorsi caudalis
pass. The vental head ends on the common ten-
don at 0.37 humerus. The triceps scapularis ten-
don almost immediately fuses with the tendon of
the ventral head of the triceps humeralis. The
resulting tendon is attached to the caudal surface
of the dorsal head of the triceps humeralis and
can be traced to the elbow. At the elbow two very
large sesamoids develop in relation to the two
parts of the triceps tendon. Distal to these sesa-
NUMBER 341
moids two tendinous slips are evident, one from
each of the sesamoids. These short, strong tendons
insert on the dorsoposterior edge of the ulna
proximal to 0.17 ulna.
Triceps humeralis
(TRI. HUM.)
FIGURES 1-6
The triceps humeralis is less massive than the
triceps scapularis but is also composed of two
heads. The shorter ventral head (Figure 3) arises
fleshy from the region of the pneumatic foramen
of the humerus. Its fibers end on a tendon at
about 0.46 humerus. The very long, slender dorsal
head (Figure 1) arises fleshy from the caudal
border of the humerus distal to about 0.39 hu-
merus. Its proximal end lies dorsal to the distal
end of the ventral head. Fibers of the dorsal head
pass caudodistally, ending on the common tendon
of the triceps scapularis and triceps humeralis. A
few of the distal fibers end on the inner sesamoid
of the elbow.
COMPARISON.?In all specimens studied there
was some exchange of fleshy fibers between the
two heads of the triceps humeralis. Watson (1883:
91) decribes such interchange of fibers for Eudyptes
chrysolophus. The dorsal head of the triceps hu-
meralis is longest in Aptenodytes, Eudyptula, and
Spheniscus; shortest in Pygoscelis; intermediate in
Eudyptes and Megadyptes.
M. BICEPS BRACHII
This muscle is generally absent in the Sphen-
iscidae. A vestigial biceps brachii was present in
a single specimen of Megadyptes antipodes. It arose
by a short delicate tendon from the dorsal surface
of the humerus deep to the pectoralis thoracica.
A very small, fleshy belly was present near the
distal end of the humerus. Insertion was by a
delicate tendon on the deep surface of the pro-
patagialis tendon over the brachialis. Filhol
(1885) does not describe this muscle for any of
the penguins he studied, including M. antipodes.
M . BRACHIALIS
(BRACH.)
FIGURES 1-6
DESCRIPTION.?The brachialis (Figure 3) arises
fleshy from the cranioventral border of the hu-
merus distal to about 0.59 humerus. The belly is
quadrilateral and well developed for this part of
the wing. Insertion is mainly fleshy on the proxi-
mal border of the radius, extending onto the
ventral surface and slightly onto the dorsal sur-
face.
COMPARISON.?The brachialis is very well de-
veloped in all penguins. There has been a fair
amount of controversy over the correct designa-
tion for this muscle. Gervais and Alix (1877:450)
consider this muscle not homologous with the
brachialis anticus (M. brachialis inferior of Ga-
dow and Selenka, 1891) of other birds because of
its insertion on the radius. Nor do they consider
it representative of a biceps, since it does not
insert on the interosseus border of the radius.
Schoepss (1829:141) describes a muscle in
Spheniscus demersus that arises from the lower part
of the cranial border of the humerus and inserts
on the radial border of the ulna near the liga-
mentous capsule of the elbow joint. Watson
(1883:92) failed to recognize the presence of this
muscle in any species of penguin that he dissected.
Gervais and Alix (1877:450) omit all reference to
it in their description of E. chrysolophus. Such a
muscle slip arising from the brachialis is some-
times present in penguins. Of the 26 specimens
examined in this study, only 8 specimens of seven
species had such a muscle slip. This slip ocurred
in one specimen each of Aptenodytes forsteri ( IS) ,
A. patagonicus (1 S), Eudyptes chrysolophus schlegeli
( 2 W ) , ? c. chrysolophus (1 S), E. pachyrhynchus (1
S), Spheniscus demersus (2 W), S. mendiculus ( 1 W ) ,
and S. magellanicus (2 W). This small slip of muscle
is a definite part of the brachialis. It separates
from the caudal border of the brachialis and
inserts by means of a short tendon on the radial
border of the ulna near the proximal end. The
presence of this slip in some specimens reinforces
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
the idea that the entire muscle is indeed the
brachialis of other birds. It has shifted its point of
insertion, a result of the extreme dorsoventral
compression of the sphenisciform wing.
M . FLEXOR CARPI ULNARIS
(F. CAR. UL.)
FIGURES 4-6
DESCRIPTION.?The flexor carpi ulnaris (Figure
4) is entirely tendinous. It arises from the distal
apex of the epicondylus medialis humeri, imme-
diately distal to the origin of the flexor digitorum
superficialis. The tendon passes along the caudal
border of the ventral surface of the ulna. Insertion
is near the middle of the ventral surface of the os
ulnare.
COMPARISON.?Similar in all penguins studied.
Watson (1883:93) also found this muscle to be
similar in all penguins he studied.
M . FLEXOR DIGITORUM SUPERFICIALIS
(F. DIG. SUP.)
FIGURES 4-6
DESCRIPTION.?This muscle (Figure 4) is en-
tirely replaced by tendon. It arises from the distal
edge of the epicondylus medialis humeri imme-
diately proximal to the flexor carpi ulnaris. The
tendon passes along the ventral surface of the
ulna adjacent to the flexor carpi ulnaris. Just
before reaching the wrist, it divides into two
branches. One of these is very short and inserts
on the cranioventral edge of the os ulnare, while
the other passes obliquely across the carpometa-
carpus to the anterior border of the wing and
fuses with the tendon of the flexor digitorum
profundus. Insertion is on the cranioventral edge
of phalanx 2, digiti majoris.
COMPARISON.?The flexor digitorum superfici-
alis is similar in all penguins studied. A small
fleshy belly is present in only one of the specimens
examined (A. patagomcus).
M . FLEXOR DIGITORUM PROFUNDUS
(F. DIG. PROF.)
FIGURES 4-6
DESCRIPTION.?The flexor digitorum profundus
(Figure 4) is represented by a single tendon, which
arises from the interosseous borders of the radius
and ulna. The tendon is indistinct and fused with
the interosseous membrane proximal to about
0.75 radius. After passing the wrist, the tendon
continues along the ventral surface of os metacar-
pale majus, the proximal phalanx of digiti ma-
joris, and finally inserts along the cranioventral
edge of the proximal and distal phalanges of
digiti majoris. The tendon fuses with the flexor
digitorum superficialis near the base of the prox-
imal phalanx of digiti majoris.
COMPARISON.?The flexor digitorum profundus
is similar in all penguins studied. A very small
belly is present in one wing of Eudyptula minor, but
absent in the other wing of this specimen. None
of the other specimens have fleshy fibers associ-
ated with the flexor digitorum profundus.
M . ULNIMETACARPALIS VENTRALIS
DESCRIPTION.?When present, the ulnimetacar-
palis ventralis is usually entirely tendinous and
arises from the ventral surface of the ulna near
the cranial border. Insertion is on the tendon of
the propatagialis near the wrist.
COMPARISON.?The ulnimetacarpalis ventralis
is absent in all specimens of Aptenodytes, Eudyptula,
and Spheniscus. In Eudyptes chrysolophus schlegeli a
very small belly is present. The ulnimetacarpalis
ventralis is present but entirely tendinous in one
specimen of E. pachyrhynchus and one specimen of
E. c. chrysolophus. One specimen of Pygoscelis papua
has an ulnimetacarpalis ventralis that arises like
that in E. pachyrhynchus. The insertion in P. papua
is on the tendon of the flexor digitorum profundus
at about 0.33 carpometacarpus. In Megadyptes the
origin is from the adjacent edges of the radius
and ulna near the distal end of these bones. It is
entirely tendinous and inserts on the caudoven-
NUMBER 341 11
tral edge of the carpometacarpus near the proxi-
mal end of the fused pollex. Schoepss (1829:152)
describes this muscle in S. demersus as having an
origin from the inner border of the ulna and
inserting into the inner side of the base of the first
radial phalanx. Neither Watson (1883:97) nor I
found this muscle in specimens of S. demersus.
Gervais and Alix (1877) and Filhol (1885) gave
no reference to such a muscle in penguins.
M . EXTENSOR METACARPI RADIALIS
(E. META. RAD.)
FIGURES 1-3
DESCRIPTION.?This is a small, weak, proxi-
mally situated muscle (Figure 1) arising tendinous
from the cranial border of the dorsal surface of
the humerus immediately proximal to the bra-
chialis. The origin is strongly attached to the
tendon of the propatagialis. The muscular fibers
are short and end on a strong tendon which, after
passing through a shallow groove near the dor-
socranial border of the radius, inserts on the
proximal end of the carpometacarpus near the
cranial border. Insertion is in common with the
extensor longus alulae.
COMPARISON.?The muscle is longest in Eudyp-
tula (0.21 radius) and shortest in Pygoscelis (0.02
radius). In the remaining genera it is of interme-
diate length. Schoepss (1829:145) reports that this
muscle arises from the humerus by two distinct
heads in penguins. I failed to find this arrange-
ment in any species of penguin, nor has any other
worker reported two heads of origin in penguins.
Watson (1883:94) reports a separate insertion
for the extensor metacarpi radialis longus (exten-
sor metacarpi radialis) and extensor metacarpi
radialis brevis in all the specimens that he dis-
sected. Such an arrangement was not present in
any specimen examined in this study. Gervais
and Alix (1877:499) and Filhol (1885:176) are in
agreement with my findings.
M. SUPINATOR
(SUPIN.)
FIGURES 1-3
DESCRIPTION.?This very weak, triangular mus-
cle (Figure 1) arises by means of a short, delicate
tendon from the heavy tendon of the extensor
digitorum communis, which arises from the dor-
sal surface of the distal end of the humeral shaft.
The muscular fibers pass distally and cranially to
insert on the dorsal surface of the radius proximal
to 0.29 radius.
COMPARISON.?The supinator is longest in
Spheniscus, intermediate in Pygoscelis and Eudyp-
tula, and shortest in Megadyptes, Aptenodytes and
Eudyptes. This muscle is absent in one specimen of
P. antarctica. It lacks muscular fibers in two spec-
imens of P. adeliae.
M . EXTENSOR DIGITORUM COMMUNIS
(E. DIG. COM.)
FIGURES 1-3
DESCRIPTION.?This muscle (Figure 1) is rep-
resented by a strong tendinous band, which arises
from the cranial edge of a wide tendinous sheet
from the epicondylus lateralis humeri. There is
no branch to the region of the fused pollex.
Insertion is on the craniodorsal surface of os
metacarpale major near the distal end, and on
both phalanges of digiti majoris nearly to the tip
of the wing. The tendon is completely fused with
the tendon of the extensor longus digiti majoris
near the middle of the major metacarpal.
COMPARISON.?A very small, fleshy belly is pre-
sent in only two of the specimens examined, one
of Eudyptes pachyrhynchus and one of Spheniscus
humboldti. In one specimen of P. papua the tendon
sends a small branch to the region of the fused
pollex. This branch ends in the fascia over the
pollex.
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
M . EXTENSOR METACARPI ULNARIS
(E. META. UL.)
FIGURES 1-3
DESCRIPTION.?The extensor metacarpi ulnaris
(Figure 1) is entirely tendinous. It arises from the
caudal edge of the tendinous sheet in common
with the extensor digitorum communis. The ten-
don passes along the craniodorsal edge of the ulna
and, after crossing the wrist, inserts on the caudal
edge of the major metacarpal at about 0.40 car-
pometacarpus.
COMPARISON.?In most specimens the insertion
is confined to the major metacarpal. Watson
(1883:96) found this muscle in Eudyptes crestatus to
insert only on the cranial border of os metacarpale
minus. None of the specimens examined in this
study have this arrangement. In all other speci-
mens, he found the muscle inserting on the caudal
border of the major metacarpal. Schoepss (1829:
150) reports the insertion on both the major and
minor metacarpals. Such an arrangement is oc-
casionally present. I have found an insertion on
both metacarpals in Megadyptes antipodes (IS),
Aptenodytes forsteri (IS), Eudyptula minor (IS), Eu-
dyptes c. chrysolophus (IS), and Spheniscus mendiculus
(IS).
M . ECTEPICONDYLO-ULNARIS
(ECT.-ULN.)
FIGURE 3
DESCRIPTION.?The ectepicondylo-ulnaris is en-
tirely tendinous. It arises from the middle of the
tendinous sheet in common with the extensor
digitorum communis and extensor metacarpi ul-
naris. The tendinous sheet arises from the dorsal
surface of the distal end of the humerus. Insertion
is on the cranial border of about the proximal
half of the ulnar shaft.
COMPARISON.?This muscle is shortest in Eu-
dyptes and longest in Eudyptula and Pygoscelis.
There is a small belly in A. patagonicus (IS), Eu-
dyptes chrysolophus schlegeli (2W), P. papua (IS),
Eudyptula m. albosignata (1W), S. demersus (1W),
and S. humboldti (1W); tendinous in all others.
The ectepicondylo-ulnaris (anconaeus) muscle
described by Reid (1835:142) and "l'ancone ex-
terne" described by Gervais and Alix (1877:449)
is either a ligament of the elbow joint or a part of
the triceps tendon. The structure described by
these authors cannot be homologized with any
muscle in other birds. They completely omit ref-
erence to the tendon that I call "ectepicondylo-
ulnaris." Watson (1883:92) did not find this mus-
cle in any species of penguin he dissected, and
Filhol (1885:175) reports the muscle to be absent
in Eudyptes crestatus.
M . EXTENSOR LONGUS ALULAE
(E. LON. AL.)
FIGURES 1-3
DESCRIPTION.?The extensor longus alulae
(Figure 2) arises by means of two heads; a small
radial head from the caudodorsal surface of the
radius beginning at about 0.43 radius and a larger
ulnar head from about the proximal half of the
cranial border of the ulnar shaft. The two bellies
fuse about midway the forearm, and the common
belly extends obliquely across the radius ending
on a tendon at about 0.80 radius. After crossing
the wrist, this tendon fuses with that of the exten-
sor metacarpi radialis. Insertion is on the proxi-
mal end of the carpometacarpus near the cranial
border of this bone.
COMPARISON.?The radial head is absent in
both wings of E. m. minor and one wing of E. m.
albosignata. Whether the absence of the radial
head in Eudyptula is significant cannot be deter-
mined on the basis of only two specimens. All
other species are similar to Eudyptes.
M . EXTENSOR LONGUS DIGITI MAJORIS
(E. LON. DIG. MAJ.)
FIGURES 2, 3
DESCRIPTION.?This muscle (Figure 2) is re-
NUMBER 341 13
placed by a tendon that arises from the distal half
of the caudal surface of the radius between about
0.53 radius and 0.82 radius. The tendon then
passes between the distal ends of the radius and
ulna, crosses the wrist, and fuses with the tendon
of the extensor digitorum communis about mid-
way of the major metacarpal. There is no trace of
a distal head.
COMPARISON.?The extensor longus digiti ma-
joris is absent in one specimen of A. forsteri and
one of A. patagonicus. It is small but partly fleshy
in one specimen of A. forsteri and very small and
tendinous in the other specimen of A. patagonicus.
In one specimen of Eudyptes pachyrhynchus there
are a few fleshy fibers associated with this muscle.
It is entirely tendinous in all other penguins
studied.
Watson (1883:97) described the extensor lon-
gus digiti majoris as being a very slender muscle
arising from the contiguous borders of the radius
and ulna and inserting into the outer side of the
second or terminal radial phalanx. Such an ar-
rangement does not occur in any of the specimens
examined in the current study. There is a con-
nection to the posterior edge of the major meta-
carpal, as well as to the extensor digitorum com-
munis in Eudyptula. Gervais and Alix (1877:451)
describe the extensor longus digiti majoris in
Eudyptes chrysocome as a very small fleshy bundle
that arises from the distal half of the interosseus
space between the radius and ulna.
My findings are in agreement with those of
Meckel and Schoepss. According to Meckel
(1828:344), this muscle is represented entirely by
tendon. Schoepss (1829:159) found that its origin
was confined to the distal end of the radius.
M . ULNIMETACARPALIS DORSALIS
(UL. META. DOR.)
FIGURES 1-3
DESCRIPTION.?The ulnimetacarpalis dorsalis
(Figure 1) arises by means of a strong, flat tendon
near the distal end of the caudodorsal edge of the
ulna. The belly is single and one of the strongest
distal to the elbow. Insertion is fleshy along an
extensive area of the caudal edge of the minor
metacarpal. The belly ends at about 0.83 carpo-
metacarpus.
COMPARISON.?Watson (1883:96) indicated the
insertion as confined to the proximal half of the
ulnar metacarpal bone in Eudyptes chrysocome and
Spheniscus demersus. The shortest belly is in Mega-
dyptes (0.76 carpometacarpus). The ulnimetacar-
palis dorsalis is a very uniformly developed mus-
cle in the Spheniscidae.
M . ABDUCTOR DIGITI MAJORIS
(ABD. DIG. MAJ.)
FIGURES 4, 5
DESCRIPTION.?This very weak muscle (Figure
5) arises from the ventral surface of the major
metacarpal near the cranial border of this bone
and from the adjacent fused pollex. The belly is
flat and bipennate. Its fibers converge distally on
a short, flat tendon. Insertion is on the base of the
proximal phalanx of the major digit.
COMPARISON.?The abductor digiti majoris is
longest in Eudyptula (0.18-0.54 carpometacarpus)
and shortest in Aptenodytes (0.32-0.78 carpometa-
carpus). The muscle is present and fleshy in all
specimens studied. However, Watson (1883:100)
reported that the muscle is represented by a
tendon in all penguins he studied, except in
Aptenodytes longirostris ( = A. patagonicus), P. papua,
and Eudyptes chrysocome, in which there was a
"distinct but weak muscular belly." According to
Meckel (1828:350) and Schoepss (1829:170) this
muscle is entirely absent in Sphenisciformes. Ger-
vais and Alix (1877:452) found it represented by
a tendon in E. chrysocome.
M . INTEROSSEUS DORSALIS
(INT. DOR.)
FIGURES 1, 2
DESCRIPTION.?The interosseus dorsalis (Figure
1) is entirely tendinous. It arises from the caudal
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
border of the major metacarpal and the cranial
border of the minor metacarpal. The tendinous
sheet that replaces the belly gives rise to a small
tendon near the distal end of the carpometacar-
pus. Insertion is on the middle of the dorsal
surface of the base of the distal phalanx of the
major digit.
COMPARISON.?A small, very weak belly is pre-
sent in one specimen of A. patagonicus and one of
S. mendiculus. Watson (1883:101) reports the mus-
cle entirely absent in one specimen of A. patagon-
icus and Eudyptula minor. In P. papua he found it
represented by a tendon without a muscular
belly. According to Schoepss (1829:172) this mus-
cle is absent in S. demersus. Gervais and Alix (1877:
453) found "the muscle, seldom fleshy."
M . INTEROSSEUS VENTRALIS
(INT. VEN.)
FIGURES 1, 2, 4, 5
DESCRIPTION.?The interosseus ventralis (Fig-
ure 5) is a weak, fleshy, bipennate muscle that
arises from the caudal border of the major meta-
carpal and the cranial border of the minor met-
acarpal on the ventral side of the carpometacar-
pus. The muscular fibers end on a slender tendon
that passes to the dorsal surface and then inserts
along the entire caudal border of the distal pha-
lanx of the major digit.
COMPARISON.?The belly is longest in Apteno-
dytes, Megadyptes, and Eudyptula; shortest in Pygos-
celis.
M . FLEXOR DIGITI MINORIS
(F. DIG. MIN.)
FIGURES 4, 5
DESCRIPTION.?This muscle (Figure 5) has a
fleshy origin from the ventral surface proximally
and the caudal surface distally of the minor meta-
carpal. The tendon is mainly on the ventral sur-
face of the belly. Insertion is mostly tendinous on
the proximally projecting tubercle on the caudal
edge of the minor digit.
COMPARISON.?The belly is longest in Apteno-
dytes and Eudyptes; shortest in Megadyptes. The
location of the distal end of the muscle is very
uniform, at 0.92 and 0.94 carpometacarpus.
The following muscles are absent in the sphen-
isciform wing: M. serratus superficialis metapa-
tagialis, M. scapulohumeralis cranialis, M. ex-
pansor secundariorum. M. pronator superficialis,
M. pronator profundus, M. entepicondylo-ul-
naris, M. abductor alulae, M. flexor alulae, M.
adductor alulae, and M. extensor brevis alulae.
Muscles of the Pelvic Appendage
M . ILIOTROCHANTERICUS CAUDALIS
(IL. TROC. CAUD.)
FIGURES 2, 10, 11
DESCRIPTION.?The iliotrochantericus caudalis
(Figure 10) arises fleshy from most of the prea-
cetabular ilium (ala preacetabularis). The belly
is very large. Its fibers converge caudally and end
on a short broad tendon that inserts on the prox-
imocranial edge of the external surface of the
femoral trochanter. The iliofemoralis externus is
fused to the iliotrochantericus caudalis except for
its extreme distal end and tendon of insertion.
COMPARISON.?The iliotrochantericus caudalis
is widest in Aptenodytes, Pygoscelis, and Eudyptula;
narrowest in Spheniscus, Megadyptes, and Eudyptes.
According to Watson (1883:103), this muscle
"arises from the whole of the external surface of
the iliac bone as far back as the posterior border
of the acetabulum, as well as from the adjoining
hollowed surface formed by the fifth, sixth, and
seventh lumbo-sacral vertebrae." In no instance
did I find the iliotrochantericus caudalis attached
to the lumbo-sacral vertebrae, nor has such an
arrangement been reported by any other worker.
NUMBER 341 15
M . ILIOTROCHANTERICUS CRANIALIS
(IL. TROC. CRAN.)
FIGURES 10-12
DESCRIPTION.?This muscle (Figure 12), much
smaller than the iliotrochantericus caudalis, arises
partly fleshy from about the caudal two-thirds of
the ventrolateral edge of the preacetabular ilium.
Carnially the belly is strongly adherent to a fi-
brous septum, which separates it from the iliotro-
chantericus caudalis. The iliotrochantericus cran-
ialis is fused to the iliotrochantericus medius, the
two muscles being barely distinguishable. Inser-
tion is by means of a short, flat tendon on the
lateral surface of the femoral trochanter, in com-
mon with the iliotrochantericus medius.
COMPARISON.?Only in Eudyptula is the origin
separate from that of iliotrochantericus medius.
In this genus the insertion, though separate, is
just distal to that of the iliotrochantericus medius.
Watson (1883:104) observed a tendency in Apteno-
dytes for the iliotrochantericus cranialis to divide
into two distinct portions, an upper and a lower,
with a cellular interval lying between them. He
failed to recognize these as representing the ili-
otrochantericus cranialis and iliotrochantericus
medius. According to Gervais and Alix (1877:
454), the iliotrochantericus cranialis in Eudyptes
chrysolophus attaches to the external border of the
ilium, "et, sur la face interne du femur, au dela du
trochanter"
M . ILIOTROCHANTERICUS MEDIUS
(IL. TROC. MED.)
FIGURES 10-12
DESCRIPTION.?The iliotrochantericus medius
(Figure 12) arises fleshy from the ventrolateral
edge of the preacetabular ilium immediately cau-
dal to the iliotrochantericus cranialis. The iliotro-
chantericus medius and iliotrochantericus crani-
alis are fused and nearly indistinguishable. Inser-
tion is in common with the iliotrochantericus
cranialis on the lateral surface of the femoral
trochanter. The femorotibialis medius partly cov-
ers this insertion.
COMPARISON.?Watson (1883:104), referring to
the iliotrochantericus medius, states, "Of this
muscle the Penguins do not possess the slightest
trace." In Aptenodytes he observed a tendency for
the iliotrochantericus cranialis "to divide into two
distinct portions, an upper and a lower, a cellular
interval lying between them." His two portions
of the iliotrochantericus cranialis probably rep-
resent the iliotrochantericus cranialis and iliotro-
chantericus medius. The bellies are fused to some
degree in all penguins. In Eudyptula the origins are
separate.
M . ILIOFEMORALIS EXTERNUS
(ILFEM. EXT.)
FIGURES 10, 11
DESCRIPTION.?The iliofemoralis externus (Fig-
ure 11) is very weakly developed. It arises fleshy
from the lateral dorsal ridge of the ilium imme-
diately caudal to the iliotrochantericus caudalis.
The origin is situated cranial to the acetabulum,
an arrangement unusual among birds. The bellies
of iliofemoralis externus and iliotrochantericus
caudalis are almost completely fused, but the
extreme distal end of the belly and the tendon of
insertion are not fused to iliotrochantericus cau-
dalis. The short, flat tendon of insertion passes
over the iliotrochanterici tendons before inserting
on the femoral trochanter. The tendon barely
reaches the ischiofemoralis, which covers the dis-
tal end of the insertion of iliofemoralis externus.
COMPARISON.?The belly of this muscle is sep-
arate from that of iliotrochantericus caudalis in
only one specimen (Megadyptes antipodes) exam-
ined. Gervais and Alix (1877:454) found the in-
sertion to be in common with the iliotrochanter-
icus caudalis, but the insertions were separate in
all penguins that I examined.
16 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
M . ILIOFEMORALIS INTERNUS
(ILFEM. INT.)
FIGURE 14
DESCRIPTION.?The iliofemoralis internus is a
small muscle arising fleshy from the ventral edge
of the preacetabular ilium just medial to the
iliotrochantericus medius. It passes caudodistally
to insert fleshy on the medial surface of the femur
near the proximal end of the femorotibialis inter-
nus.
COMPARISON.?This muscle is very uniformly
developed, showing no significant variations in
penguins. However, Meckel (1828:353) thought
it to be absent in the Spheniscidae.
M. AMBIENS
FIGURES 10-14
DESCRIPTION.?The ambiens (Figure 13) is a
large muscle, arising mostly fleshy from the ven-
tral border of the acetabulum. The flattened belly
lies on the medial side of the thigh, and terminates
on a strong, flat tendon at about 0.86 femur. The
tendon passes in a shallow groove (Figure 14) on
the cranial surface of the patella, then through
the patellar tendon to the lateral side of the knee.
The tendon ends opposite the proximal part of
the fibula by inserting (Figure 12) on the tendon
of origin of the cranial head of the perforated
flexors.
COMPARISON.?The ambiens is shortest in Py-
goscelis and Eudyptula, and is longest in Aptenodytes.
M . ILIOTIBIALIS CRANIALIS
(ILTIB. CRAN.)
FIGURES 1,9, 13
DESCRIPTION.?The iliotibialis cranialis (Figure
9) is a very powerful muscle, making up the
anterior limit of the thigh. The origin is aponeu-
rotic from the caudal end of the fused thoracic
spinous ridge and fleshy from the cranial and
cranio ventral edges of the ilium. There is a strong
tendinous connection with the aponeurosis of the
iliotibialis. Insertion (Figure 13) is fleshy on the
medial and cranial surfaces of the patella and
patellar tendon.
COMPARISON.?No major differences were
noted other than variations in relative width, the
belly being broadest in Eudyptula and Megadyptes.
M. ILIOTIBIALIS
(IL. TIB.)
FIGURES 2, 9, 13
DESCRIPTION.?The iliotibialis (Figure 9) is a
weakly developed, thin sheet of muscle that arises
by means of an aponeurosis from the spinous
processes opposite the acetabulum. This aponeu-
rosis is attached to the belly of the iliotibialis
cranialis cranially and the biceps femoris cau-
dally. The postacetabular part of the iliotibialis
is absent. The belly is thin along its cranial
margin and much thicker along its caudal border.
The center of this muscle is aponeurotic distally.
Insertion is tendinous on the crista cnemialis cran-
ialis of the tibia in common with the femorotibi-
alis medius and femorotibialis externus. The
iliotibialis tendon forms a part of the patellar
tendon.
COMPARISON.?The iliotibialis is a uniformly
developed muscle in all species examined. Ac-
cording to Garrod (1873:643), the postacetabular
portion of this muscle is absent in penguins, which
is consistent with my observations. Watson (1883:
112) reports the presence of this portion, although
reduced to a minimum size, in every species he
examined.
M . FEMOROTIBIALIS EXTERNUS
(FEM. TIB. EXT.)
FIGURE 12
DESCRIPTION.?The femorotibialis externus
(Figure 12) is a very small muscle. It arises from
the caudolateral surface of the femur beginning
NUMBER 341 17
at about 0.65 femur. Insertion is in common with
the caudal margin of the patellar tendon.
COMPARISON.?In most penguins the femoroti-
bialis externus can be partially separated at either
its proximal or distal end. Eudyptes pachyrhynchus
and Megadyptes antipodes have the most distinct
femorotibialis externus. The muscle is not distin-
guishable in Eudyptula and is either absent or very
vague in Aptenodytes and Pygoscelis.
M . FEMOROTIBIALIS MEDIUS
(FEM. TIB. MED.)
FIGURES 10, 11, 13, 14
DESCRIPTION.?The femorotibialis medius (Fig-
ure 10) consists of a large fleshy mass which arises
from a very extensive area on the lateral and
cranial surfaces of the femoral shaft from the
trochanter to the distal condyles. The belly is
strong and notched proximally by the insertion
of the iliotrochantericus cranialis and iliotrochan-
tericus medius. Insertion is mostly fleshy on the
proximal surface of the patellar tendon.
COMPARISON.?The femorotibialis medius is
similar in all forms examined.
M . FEMOROTIBIALIS INTERNUS
(FEM. TIB. INT.)
FIGURES 13, 14
DESCRIPTION.?This long, slender muscle (Fig-
ure 14) arises from the whole length of the medial
surface of the femoral shaft, extending proximally
to the insertion of the iliofemoralis internus. The
belly is not divided into superficial and deep
parts. Insertion is by a short, flat tendon on the
cranial cnemial crest of the tibia.
COMPARISON.?The femorotibialis internus is
similar in all forms examined.
M . CAUDO-ILIO-FEMORALIS
This muscle complex is composed of two mus-
cles: M. caudofemoralis and M. iliofemoralis,
which are separate for most of their extent but
have a common insertion.
M . CAUDOFEMORALIS
(CAUD. FEM.)
FIGURES 9, 10
DESCRIPTION.?The caudofemoralis (Figure 10)
arises from about the cranial half of the pygostyle
and from the last one or two free coccygeal ver-
tebrae. The caudal end of the origin is tendinous.
The flat, spindle-shaped belly passes craniodis-
tally toward the femur. Just before fusing with
the iliofemoralis it forms a short tendon. Insertion
is in common with the iliofemoralis on the caudal
surface of the femur between about 0.50 and 0.76
femur.
COMPARISON.?The caudofemoralis is very sim-
iar in all penguins examined in this study and by
other workers.
M . ILIOFEMORALIS
(IL. FEM.)
FIGURES 9, 10
DESCRIPTION.?The iliofemoralis (Figure 10)
arises from the ventrolateral surface of the crista
iliaca dorsolateralis. The origin is mainly tendi-
nous but includes a small fleshy area posteriorly.
The belly is a broad, thin sheet, distinctly nar-
rower at the distal end. Insertion is in common
with the caudofemoralis as described above.
COMPARISON.?The origin of the iliofemoralis
varies somewhat among genera. It is entirely
fleshy in Spheniscus, mostly fleshy in Aptenodytes,
mainly tendinous in Eudyptes, and entirely tendi-
nous in Pygoscelis, Eudyptula, and Megadyptes.
I was unable to find the variation that Watson
(1883:106) described for the insertion of the
caudo-ilio-femoralis. He reported that the inser-
tion is confined to the middle third of the femoral
shaft in S. demersus and S. magellanicus, to the lower
third in Eudyptes chrysolophus, and to the lower
two-thirds in Aptenodytes. The means for the distal
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
end of this muscle's insertion ranged from 0.71 to
0.79 femur.
M . FLEXOR CRURIS LATERALIS
(FL. CR. LAT.)
FIGURES 9, 10
DESCRIPTION.?This very powerful muscle (Fig-
ure 9) arises mainly fleshy from the extreme
caudal tip of the dorsal border of the ilium and
from the transverse processes of about the first
through sixth free caudal vertebrae. It inserts by
means of a flat tendon in common with the flexor
cruris medialis on the medial surface of the tibia
between the middle and internal heads of the
gastrocnemius. The insertion extends from about
0.16 to about 0.31 tibiotarsus. The accessory head
is absent.
COMPARISON.?This muscle is very uniformly
developed in the Spheniscidae. There is some
difference in the relative width of the belly. It is
widest in Aptenodytes and Pygoscelis, and narrowest
in Eudyptes and Eudyptula. The accessory head is
absent in all penguins.
M . FLEXOR CRURIS MEDIALIS
(FL. CR. MED.)
FIGURES 10, 11, 13, 14
DESCRIPTION.?The flexor cruris medialis (Fig-
ure 11) arises fleshy from the caudoventral edge
of the ischium and the extremity of the pubis,
including the cartilaginous extension of that
bone. The belly passes obliquely craniodistally
and, after being joined by a slip from the external
oblique muscle, is inserted fleshy on the caudo-
medial surface of the tibia just distal to the caput
tibia. Insertion is in common with the flexor cruris
lateralis. In a more typical bird, such as Gallus,
the flexor cruris medialis becomes tendinous be-
fore joining the flexor cruris lateralis to contribute
to their common insertion. The fleshy fibers of
the slip from the external oblique muscle insert
on an extensive length of the distal part of the
caudal border of the flexor cruris medialis and
onto the medial surface of that muscle just before
its insertion.
COMPARISON.?In Megadyptes, the slip from the
external oblique muscle inserts along nearly the
entire length of the caudal border of the flexor
cruris medialis. In the other genera this union is
not as extensive.
The origin of this muscle is most extensive in
Eudyptula and least extensive in Aptenodytes. The
belly is widest in Aptenodytes, intermediate in Py-
goscelis, and narrowest in the remaining genera.
M . ILIOFIBULARIS
(ILFIB.)
FIGURES 9, 10
DESCRIPTION.?The iliofibularis (Figure 9) is a
very well developed muscle. It arises fleshy from
the entire dorsolateral crest of the ilium posterior
to the iliotibialis. The cranioproximal edge of the
belly is fused to the caudal edge of the iliotibialis.
The belly is not covered by the iliotibialis. Prox-
imal to the knee the converging fibers form a very
strong, laterally compressed tendon, which passes
through the biceps loop and continues distally to
insert (Figure 10) on a well-defined tubercle on
the caudolateral surface of the fibula. The inser-
tion extends between about 0.30-0.35 tibiotarsus.
The tendon appears to be composed of several
tendinous fascicles.
COMPARISON.?The iliofibularis is a very uni-
formly developed muscle in penguins.
M . ISCHIOFEMORALIS
(ISCH. FEM.)
FIGURES 10, 11
DESCRIPTION.?The muscle (Figure 11) arises
from most of the lateral surface of the area occu-
pied by the flexor cruris medialis and from the
ventral edge of the caudal part of the dorsolateral
crest of the ilium medial to the iliofibularis. The
fibers pass cranially, converging on a stout tendon
NUMBER 341 19
that inserts on the femoral trochanter caudal to
the insertions of the iliotrochantericus cranialis
and medius.
COMPARISON.?Except for some variation in
length, this is a very uniformly developed muscle.
It is longest in Aptenodytes and shortest in Eudyp-
tula.
M . OBTURATORIUS MEDIALIS
(OBT. MED.)
FIGURES 12, 13
DESCRIPTION.?The obturatorius medialis (Fig-
ure 13) is an elongate oval muscle. It arises from
the inner surface of most of the ischium caudal to
the obturator foramen and from most of the
medial surface of the pubis. Anteriorly the muscle
enters the obturator foramen and passes to the
outside of the pelvis, where the fibers end on a
strong tendon that inserts on the caudal edge of
the femoral trochanter just caudal to the insertion
of the ischiofemoralis. Insertion is in common
with the obturatorius lateralis and is partly fleshy.
COMPARISON.?The width is about 0.25 the
length of the muscle in Aptenodytes. In Spheniscus it
is about 0.44 the length of the muscle.
M . OBTURATORIUS LATERALIS
(OBT. LAT.)
FIGURE 12
DESCRIPTION.?The obturatorius lateralis is a
small quadrilateral muscle that arises from the
lateral surface of the pelvis adjacent to the obtur-
ator foramen. Insertion is on the caudal border of
the femoral trochanter in common with the ob-
turatorius medialis.
COMPARISON.?This muscle is very similar in
all forms examined.
M . PUBO-ISCHIO-FEMORALIS
(PUB.-IS.-FEM.)
FIGURES 9-13
DESCRIPTION.?This very powerful muscle (Fig-
ure 12) arises mainly fleshy from almost the entire
length of the lateral surface of the pubis caudal
to the acetabulum, from part of the cartilaginous
extension of this bone, and from a less extensive
area on the ventrolateral edge of the ischium.
The belly is clearly divided into lateral and me-
dial heads, especially anteriorly. The fibers pass
craniodistally to insert on the caudal border of
the femoral shaft distal to about 0.37 femur. The
insertion is mostly fleshy, but a few of the caudal
fibers insert by means of a tendon immediately
above the internal condyle of the femur. This
muscle is firmly fused to the gastrocnemius pars
medialis for a considerable length.
COMPARISON.?Although the pubo-ischio-fe-
moralis shows no major variations in penguins,
there is a slight variation in the relative width of
the belly; it is widest in Aptenodytes, Pygoscelis, and
Spheniscus, narrowest in Megadyptes. There is also
some variation in the length of origin along the
pubis. It is longest in Aptenodytes and shortest in
Eudyptes.
M . TIBIALIS CRANIALIS
(TIB. CRAN.)
FIGURES 10, 11, 13-16
DESCRIPTION.?The tibialis cranialis (Figure
10) arises by two distinct heads. The lateral head
arises by means of a strong tendon from the
cranial surface of the lateral condyle of the femur.
The medial head has a fleshy origin from a very
small part of the lower border of the patella, the
intermuscular septum, which separates the tibi-
alis cranialis from the gastrocnemius pars medi-
alis, and from the cranial cnemial crest of the
tibia. The medial head is also tendinous from a
very narrow area on about the proximal fourth
of the cranial border of the tibia. The heads unite
and form a single tendon opposite the tibiotarsus.
The tendon passes beneath a heavy fibrous loop
(Figure 15) just above the distal malleoli, tra-
verses the intertarsal joint, and inserts on a tu-
bercle of metatarsus III at about 0.34 tarsometa-
tarsus. It sends a smaller branch laterally to meta-
tarsus II.
20 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
COMPARISON.?Watson (1883:118) describes a
single insertion on metatarsus III in penguins.
Only in S. mendiculus did he find a branch to
metatarsus II. I found a branch to metatarsus II
in most penguins. Only in Pygoscelis papua (IS), P.
antarctica (IS), Eudyptes chrysolophus schlegeli (IS),
and E. chrysocome (IS) did I find a single insertion
on metatarsus III.
M . EXTENSOR DIGITORUM LONGUS
(EXT. DIG. L.)
FIGURES 9, 12, 14, 15
DESCRIPTION.?This muscle (Figure 12) occu-
pies the cranial surface of the tibiotarsus imme-
diately caudal to the tibialis cranialis. The origin
is fleshy from a small area on the distal border of
the patella and from about the proximal half or
less of the craniomedial surface of the tibia. The
weak bipennate belly tapers distally; ending on a
tendon that passes under the retinaculum exten-
sorium tibiotarsi in common with the tibialis
cranialis and through a bony canal on the distal
end of the tibiotarsus, crosses the intertarsal joint,
slides under the retinaculum extensorium tarso-
metatarsi, and expands into an aponeurotic tri-
angle that, upon reaching the base of the three
digits, divides sending a branch to each digit
(Figure 15). The middle branch bifurcates more
or less vaguely near the base of digit III; these are
connected by an aponeurosis.
First digit: There is no branch to the first digit.
Second digit: The branch to the second digit
inserts mainly on the distal end of phalanx 1 and
the bases of the second and third phalanges.
Third digit: The medial branch inserts mainly
on the distal end of phalanx 1 and proximal end
of phalanx 2. The long lateral branch gives off a
branch laterally to the base of phalanx 3, then
continues distally. It inserts mainly on the bases
of the second, third, and ungual phalanges.
Fourth digit: The branch to the fourth digit
inserts mainly on the bases of the second, third,
fourth, and fifth phalanges.
COMPARISON.?This is a very uniformly devel-
oped muscle in penguins.
M . FIBULARIS LONGUS
(FIB. LONG.)
FIGURES 9-11, 15, 18
DESCRIPTION.?The fibularis longus (Figure 9)
occupies the cranial and craniolateral surfaces of
the shank. It arises tendinous from the cranial
surface of the cranial cnemial crest of the tibia,
by a strong aponeurosis from a long narrow line
on the craniolateral border of the tibia, and partly
fleshy from about the middle third of the lateral
border of the fibula. The muscular fibers end on
a tendon above the intertarsal joint at about 0.78
tibiotarsus. Just above the malleolus, the tendon
gives off a very broad flattened expansion to the
lateral side of the proximal end of the tibial
cartilage. This expansion is strongly attached to
the lateral surface of the lateral malleolus. After
passing the intertarsal joint, the tendon divides
into a cranial and a caudal branch. The cranial
tendon passes down the lateral side of metatarsus
IV and the fourth digit, ending on the penulti-
mate phalanx of digit IV. The caudal branch
(Figure 18) passes obliquely caudodistally and
unites with the tendon of the flexor perforatus
digiti III.
COMPARISON.?No significant variations were
noted in penguins.
M. FIBULARIS BREVIS
(FIB. BREV.)
FIGURES 9-12
DESCRIPTION.?The fibularis brevis (Figure 12)
is a very slender muscle that arises from about
the distal half of the fibula and the adjacent
border of the tibia. Its tendon passes caudodistally
across the lateral malleolus and, after crossing the
intertarsal joint, inserts on the lateral edge of the
tarsometatarsus.
COMPARISON.?No significant differences occur
NUMBER 341 21
in the Spheniscidae. The fibularis brevis is an
extremely weak muscle in penguins. Watson
(1883:119) has this muscle arising from the upper
two-thirds of the fibula. The most extensive origin
occurs in Megadyptes, in which it arises from most
of the length of the fibula. In most of the other
penguins, the origin is confined to the distal two-
thirds of the fibula.
M . GASTROCNEMIUS
(GAS.)
FIGURES 9-13
DESCRIPTION.?The gastrocnemius forms the
superficial musculature of most of the medial and
posterior surface of the shank and arises by three
distinct heads: pars lateralis, pars intermedia, and
pars medialis.
Pars lateralis (p. LAT.: Figures 9, 12, 13): This
head (Figure 9) arises by a strong tendon from
the femur just above the proximolateral edge of
the external condyle and partly fleshy from the
length of the biceps loop. The belly broadens over
the caudolateral surface of the shank and ends on
a tendon at about 0.74 tibiotarsus. This tendon
joins that of the pars medialisjust above the tibial
cartilage.
Pars intermedia (p. INT.: Figures 12, 13): The
intermediate head of the gastrocnemius (Figure
12) has a tendinous origin from the caudal edge
of the proximal end of the medial condyle of the
femur. Proximally the belly is strongly fused to
the pubo-ischio-femoralis. Distally the belly of
the pars intermedia joins the pars medialis at
about 0.40 tibiotarsus. This union is partly fleshy.
Pars medialis (p. MED.: Figures 10-13): The me-
dial head of the gastrocnemius (Figure 13) arises
mainly fleshy from the cranial cnemial crest of
the tibia, from the medial edge of the patella, and
from the aponeurosis, separating it from the ti-
bialis cranialis. The common tendon of the inter-
mediate and medial heads joins the tendon of the
lateral head just above the tibial cartilage form-
ing a very strong tendon that, after passing the
intertarsal joint, divides into two stout branches.
The heavier intermediate branch has a broad
insertion near the proximal end of metatarsus II;
the lateral branch inserts more distally on the
caudolateral border of metatarsus IV, a little
below the middle.
COMPARISON.?Very little variation was noted
in the gastrocnemius, although the length of the
belly shows some variation. It is longest in Mega-
dyptes and much shorter in the other genera.
M. PLANTARIS
(PLAN.)
FIGURE 14
DESCRIPTION.?The plantaris is a short, flat
muscle that arises fleshy from about the proximal
third of the caudal border of the tibia. About
halfway down the shank, the belly ends on a
flattened tendon, which rapidly tapers to a small
oval form. Insertion is on the proximal end of the
medial side of the tibial cartilage.
COMPARISON.?The belly is longest in Mega-
dyptes and shortest in Aptenodytes and Pygoscelis.
Position of the Flexor Tendons Passing the
Intertarsal Joint
DESCRIPTION.?Removal of the gastrocnemius
tendon from the posterior surface of the joint
capsule exposes a bundle of three tendons on the
caudolateral side. The most cranial of these is a
flexor perforatus digiti III, which forms a sheath
around the flexor perforans et perforatus digiti
III medially and the flexor perforatus digiti IV
laterally. The remaining four tendons traverse
separate canals. On the caudomedial side is a
canal for the flexor perforans et perforatus digiti
II. Cranial and slightly lateral there is a canal for
the flexor perforatus digiti II. Lateral to the flexor
perforatus digiti II is a canal for the flexor hallucis
longus. The most cranial canal encloses the ten-
don of the flexor digitorum longus.
COMPARISON.?Most penguins adhere to the
above pattern. However, some species of Eudyptes,
Spheniscus, and Eudyptula have the flexor perforans
22 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
et perforatus digiti III caudal to the flexor perfor-
atus digiti IV.
M . FLEXOR PERFORANS ET PERFORATUS DIGITI II
(F. P. ET P. D. II)
FIGURES 9, 18
DESCRIPTION.?This muscle (Figure 9) has a
very broad origin extending from the gastrocne-
mius pars lateralis to the cranial cnemial crest,
tendinous from the external condyle of the femur,
the joint capsule, the underlying biceps loop, and
the cranial cnemial crest. The belly is strongly
attached to the gastrocnemius pars lateralis near
the extreme proximal end of this muscle and to
the flexor perforans et perforatus digiti HI and
the fibularis longus. The belly ends a little above
the middle of the shank on a flat tendon, which
narrows as it passes distally. Near the base of the
second digit the tendon perforates that of the
flexor perforatus digiti II before inserting mainly
on the distal end of phalanx 1 and proximal end
of phalanx 2. There is also a strong attachment
to the base of phalanx 1.
COMPARISON.?This muscle in Eudyptes chrysolo-
phus has an additional origin from the tibia and
fibula, according to Gervais and Alix (1877:460).
I failed to find such an origin in any specimen
examined. They also describe two fleshy sheets
comprising this muscle. Such an arrangement
occurred in several specimens ofSpheniscus, Apteno-
dytes, and Pygoscelis, but shows intraspecific vari-
ation.
M . FLEXOR PERFORANS ET PERFORATUS DIGITI III
(F. P. ET P. D. HI)
FIGURES 9, 18
DESCRIPTION.?This muscle (Figure 9) arises
partly fleshy from the head of the fibula, fleshy
from a narrow line on the lateral surface of the
fibula, to a point just distal to the iliofibularis
insertion, partly tendinous from the lateral edge
of the cranial cnemial crest, the lateral side of the
joint capsule, and from the patellar tendon. The
belly is larger than that of the flexor perforans et
perforatus digiti II. Just distal to the middle of
the shank, the belly ends on a tendon that is
broad proximally. Near the base of the third
digit, the tendon perforates that of the flexor
perforatus digiti HI and, in turn, is perforated by
the tendon of the flexor digitorum longus near
the proximal end of phalanx 2. Insertion is on the
distal end of phalanx 2 and proximal end of
phalanx 3 by two branches that result from the
perforation by the flexor digitorum longus.
COMPARISON.?The flexor perforans et perfor-
atus digiti HI is very similar in all penguins.
M . FLEXOR PERFORATUS DIGITI II
(FLEX. PER. D. II)
FIGURES 11, 18
DESCRIPTION.?This muscle arises fleshy from
the intercondylar space in common with the me-
dial and lateral heads of flexor perforatus digiti
HI and flexor perforatus digiti IV The belly
separates from the common muscle mass at ap-
proximately the middle of the shank. At about
0.75 tibiotarsus, the belly terminates on a tendon
that, after being perforated by the flexor perfor-
ans et perforatus digiti II near the base of phalanx
1 digit II, is inserted on the base of the proximal
phalanx.
COMPARISON.?The belly is longest in Apteno-
dytes and shortest in Eudyptes. Except for this
difference in length, the flexor perforatus digiti II
is very similar in all penguins.
M . FLEXOR PERFORATUS DIGITI III
(FLEX. PER. D. Ill)
FIGURES 9-11, 14, 18
DESCRIPTION.?The flexor perforatus digiti III
(Figure 10) arises from the regio intercondyloidea
of the femur by means of a broad, flat tendon.
This tendon is strongly attached to the cranial
surface of the flexor perforatus digiti IV belly. It
NUMBER 341 23
also arises in common with the flexor perforatus
digiti II and flexor perforatus digiti IV from the
head of the fibula and lateral condyle of the
femur by means of a short tendon. The belly is
notched slightly proximally. A tendinous sheet
extends between these two parts of the belly. The
flexor perforatus digiti III is the longest of the
perforated flexors. Near the distal end of the
tibiotarsus, the tendon forms a sheath around the
more caudally situated tendons of the flexor per-
forans et perforatus digiti III and flexor perforatus
digiti IV. Near the middle of the tarsometatarsus,
the tendon is very strongly attached to the caudal
branch of the fibularis longus tendon. Near the
base of phalanx 1, the tendon is perforated by
that of the flexor perforans et perforatus digiti
III. Insertion is on the distal end of phalanx 1.
There is no vinculum between the tendons of the
flexor perforatus digiti III and flexor perforans et
perforatus digiti HI.
COMPARISON.?The flexor perforatus digiti III
is a very uniformly developed muscle except for
some variation in the length of the belly. There
is no vinculum between the tendons of the flexor
perforatus digiti III and flexor perforans et per-
foratus digiti III in any penguin examined.
M . FLEXOR PERFORATUS DIGITI I V
(FLEX. PER. D. IV)
FIGURES 10, 11, 18
DESCRIPTION.?The flexor perforatus digiti IV
(Figure 10) has a fleshy origin from the regio
intercondyloidea of the femur. It also arises by a
short tendon from the head of the fibula and
lateral condyle of the femur in common with the
flexor perforatus digiti II and flexor perforatus
digiti III. This short tendon passes medial to the
tendon of insertion of the iliofibularis. The belly
gives rise to a tendon at about 0.63 tibiotarsus.
Near the base of the fourth digit, the tendon
dilates before dividing into four branches (Figure
18). The lateral branch (branch 1) fuses with the
medial branch (branch 4) near the middle of
phalanx 1 before inserting on the proximal end
of phalanx 2. The two middle branches (branches
2 and 3) fuse near the base of phalanx 2 and
insert on the base of phalanx 3. The flexor digi-
torum longus tendon to the fourth digit passes
between branches 1 and 4 and then between
branches 2 and 3.
COMPARISON.?The insertion of the flexor per-
foratus digiti IV exhibits several variations. In
Eudyptes, Spheniscus, and Megadyptes, the tendons
exhibit the same pattern as that described for E.
pachyrhynchus. Branch 1 remains separate in Eu-
dyptula and inserts on the distal end of phalanx 1
and proximal end of phalanx 2, while branches
2 and 4 fuse near the distal half of phalanx 1
before inserting on the proximal end of phalanx
2. In Eudyptula, branch 3 remains separate and
inserts on the base of phalanx 3, the tendon of
the flexor digitorum longus to the fourth toe
passing lateral to branch 3. In Pygoscelis, branches
1 and 4 fuse before inserting on the base of
phalanx 2. Branch 2 remains separate and inserts
on the proximal end of phalanx 3. Branch 3
likewise remains separate but inserts on the base
of phalanx 4. The flexor digitorum longus tendon
to the fourth digit passes between branches 1 and
4 and then between branches 2 and 3. None of
the branches fuse in Aptenodytes. Branches 1 and
4 insert on the base of phalanx 2; while branches
2 and 3 insert on the bases of phalanx 3 and
phalanx 4, respectively. The flexor digitorum lon-
gus tendon passes medial to branch 1 and lateral
to branches 2, 3, and 4. The belly is longest in
Megadyptes and shortest in Pygoscelis and Eudyptes.
M . FLEXOR HALLUCIS LONGUS
(F. HAL. L.)
FIGURES 10-12, 14, 15, 18
DESCRIPTION.?The flexor hallucis longus (Fig-
ure 12) arises fleshy from the regio intercondyloi-
dea of the femur in common with the perforated
flexors. Its belly is large in relation to the size of
the hallux. About midway the tibiotarsus, the
short belly ends on a broad, flat tendon, which
tapers as it passes distally toward the intertarsal
24 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
joint. The tendon trifurcates opposite the tarso-
metatarsus just before fusing with the flexor dig-
itorum longus. On the medial side, there is a
fibrous connection between the tendons of the
flexor hallucis longus and flexor digitorum longus
immediately proximal to the trifurcation. This
connection has some resemblance to a vinculum.
Of the three very short branches of the flexor
hallucis longus, the one that fuses with the flexor
digitorum longus tendon to the fourth digit is the
strongest. The branch to the third digit is very
weak. In addition to these three tendons, a fourth
very delicate tendon arises from the medial edge
of the flexor hallucis longus opposite the trifur-
cation. It inserts on the base of the ungual pha-
lanx of the hallux.
COMPARISON.?This muscle shows very little
variation among penguins. In several specimens
of Pygoscelis, I was unable to find the branch to
the hallux. Poor preservation may account for
this omission. The belly is longest in Spheniscus
and shortest in Aptenodytes.
M . FLEXOR DIGITORUM LONGUS
(F. DIG. L.)
FIGURES 9-12
DESCRIPTION.?This powerful deeply situated
muscle (Figures 12, 14) arises from most of the
caudal and medial borders of the tibia distal to
the popliteus, from the interosseus membrane,
and the adjacent border of the fibula. The belly
gives rise to a strong tendon near the distal end
of the tibiotarsus. The tendon trifurcates near the
proximal end of the tarsometatarsus. The three
branches, after uniting with those of the flexor
hallucis longus, insert on the bases of the ungual
phalanges of digits 2, 3, and 4. There is a short
fibro-elastic branch to the base of each phalanx
except phalanx 1.
COMPARISON.?No important variations were
noted.
M. POPLITEUS
DESCRIPTION.?This small, quadrilateral mus-
cle has a fleshy origin from the proximal end of
the caudomedial border of the fibula. Insertion is
fleshy near the proximal end of the caudal surface
of the tibial shaft. The muscle broadens before
reaching its insertion and is fleshy throughout.
COMPARISON.?The popliteus is a very uni-
formly developed muscle in penguins.
M . EXTENSOR HALLUCIS LONGUS
(EXT. HAL. L.)
FIGURES 15, 16
DESCRIPTION.?The origin of this small muscle
(Figure 15) is fleshy from the dorsal and medial
surfaces of the rudimentary metatarsus I and
from the ligament that connects the first to the
second metatarsal. The belly ends near the prox-
imal end of phalanx 1. The tendon of insertion is
separated from the surrounding connective tissue
with difficulty. It traverses the dorsal surface of
the hallux and is inserted along most of the length
of phalanx 1 and on the base of the ungual
phalanx.
COMPARISON.?The origin extends onto meta-
tarsus III in a specimen of A. forsteri (1 S), P.
antarctica (1 S), E. pachyrhynchus (1 S), and M.
antipodes ( I S ) .
M . EXTENSOR BREVIS DIGITI H I
(EXT. BREV. D III)
FIGURES 15, 16
DESCRIPTION.?The origin (Figure 16) is fleshy
from most of the cranial surface of metatarsus III
and the groove between metatarsus II and meta-
tarsus III. The broad belly terminates on a short,
flat tendon that inserts on the base of the first
phalanx of digit III. The broad tendon is grown
into the joint capsule.
COMPARISON.?This muscle varies only in
length. The belly is shortest in Pygoscelis and
longest in Aptenodytes and Eudyptula.
NUMBER 341 25
M . EXTENSOR BREVIS DIGITI I V
(EXT. BREV D. IV)
FIGURES 14-16
DESCRIPTION.?The origin (Figure 16) is fleshy
from the cranial and medial surfaces of metatar-
sus IV and the lateral edge of metatarsus III. Its
belly is wide and occupies most of the cranial
surface of metatarsus IV. Insertion is by a short
tendon on the medial edge, proximal end, of
phalanx 1, digit IV. The tendon passes through
a groove between metatarsus III and metatarsus
IV. There is no bony canal.
COMPARISON.?The belly of extensor brevis dig-
iti IV is longest in Eudyptula and shortest in
Aptenodytes.
M . ABDUCTOR DIGITI II
(ABD. DIG. II)
FIGURES 13-18
DESCRIPTION.?This muscle (Figure 16) arises
fleshy from most of the cranial and craniomedial
borders of metatarsus II. The belly is wide prox-
imally and narrow distally. It ends on a short,
strong tendon at about 0.66 tarsometatarsus. In-
sertion is on the dorsomedial edge of the base of
phalanx 1, digit II.
COMPARISON.?The abductor digiti II is a uni-
formly developed muscle in penguins. In some
specimens there is a division in the belly distally.
This division tends to be most obvious in Apteno-
dytes.
M . FLEXOR HALLUCIS BREVIS
DESCRIPTION.?The flexor hallucis brevis is pre-
sent in only five of the six specimens of Pygoscelis
examined. In these it has a fleshy origin from a
very small area on metatarsus II at the base of
metatarsus I and from most of the plantar surface
of metatarsus I. The belly is very small. Insertion
is by a short tendon on the base of the distal
phalanx.
COMPARISON.?This muscle is absent in all
specimens of Eudyptes examined. Watson (1883:
126) was unable to find this muscle in any of the
specimens examined in his study. Meckel (1828)
does not describe this muscle for penguins. Reid
(1835:145) and Gervais and Alix (1877:461) de-
scribe this muscle in A. patagonicus and E. chryso-
iophus, respectively. The muscle is apparently pre-
sent in only a small percentage of penguins. The
high frequency of its occurrence in Pygoscelis sug-
gests that this muscle may be characteristic in
this genus and, hence, of taxonomic importance.
A larger sample is needed for verification.
M . LUMBRICALIS
DESCRIPTION.?The lumbricalis arises from the
cranial surface of the deep flexor tendon just
distal to the point of trifurcation. The muscle is
very vague and appears mostly fibrous. Insertion
is on the joint pulley near the base of digit III.
COMPARISON.?The lumbricalis is very weak in
penguins, and most specimens have only a very
small vestige when present. Poor preservation
may account for its absence in several specimens.
M . ABDUCTOR DIGITI I V
(ABD. DIG. IV)
FIGURES 17, 18
DESCRIPTION.?The origin (Figure 18) is fleshy
from most of the caudal border of metatarsus IV.
The belly is wider proximally and narrow distally.
Insertion is by a short tendon on the lateroplantar
edge of the base of the first phalanx of digit IV.
The tendon is strongly fused with the connective
tissue over the joint.
COMPARISON.?This is a uniformly developed
muscle in penguins.
The following muscles are absent in the sphen-
isciform leg: M. extensor proprius digiti III, M.
adductor digiti II, and M. adductor digiti IV.
Discussion and Conclusions
The pectoral musculature of penguins is unlike
that of any other group of birds. A number of
26 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
wing muscles are absent, most remarkably the
biceps. The biceps is absent only in penguins.
Several other wing muscles, the expansor secun-
dariorum, scapulohumeralis cranialis, and serra-
tus superflcialis metapatagialis, are also absent in
penguins. The pronator superflcialis and pronator
profundus are likewise absent, a loss associated
with the inability of the wing to be rotated at the
elbow. Somewhat surprising, because of the lack
of a well-developed patagial wing fold, is the
presence of a well-developed propatagialis muscle
whose tendon inserts along much of the length of
the wing and is strongly attached to the alar
aponeurosis. Beddard (1898:397) and Watson
(1883:88) have this tendon passing all the way to
the extremity of the last phalanx. The latissimus
dorsi is peculiar in that its two parts end in long,
slender tendons that pass through a fibrous loop
from the scapula. The latissimus dorsi metapa-
tagialis varies greatly in development. It is an
extremely wide muscle in Aptenodytes and very
narrow in Pygoscelis and Eudyptula. With the ex-
ception of Pygoscelis, the development seems to be
related to the size of the bird. The insertion of
this muscle in penguins is on the skin along the
lateral line of the trunk instead of near the hu-
meral feather tract as in most birds. Most of the
muscles acting across the shoulder joint are very
well developed, a reflection of the peculiar action
of the wings during underwater flight. The pec-
toralis thoracica is so large that it meets its fellow
in the midline over the carina, a condition similar
to that in Tinamous (Watson, 1883:397). The
supracoracoideus is very strongly developed in
relation to the pectoralis. These two muscles are
the prime movers of the wing during underwater
flight. Although the short head of the deltoideus
minor is very small and weak, the long head is
large and aids the supracoracoideus in raising the
wing. The deltoideus major, on the other hand,
is a very weak muscle.
Only nine muscles distal to the shoulder have
fleshly fibers. The triceps has a peculiar arrange-
ment in penguins. Both the triceps scapularis and
triceps humeralis consist of two heads. One head
of the triceps scapularis arises from the clavicle
and acromial process of the scapula; the other
head arises fleshly from the dorsolateral border of
the scapula in much the same position as the
aponeurotic anchor (George and Berger, 1966:
335) arises in many other birds. The triceps hu-
meralis has both a dorsal and ventral head arising
from the humerus. The brachialis is peculiar in
penguins in that it inserts on the radius as a
consequence of the extreme dorsoventral com-
pression of the wing, an adaptation to underwater
flight. Occasionally a small slip separates from
the caudal edge of the muscle and inserts on the
ulna in a position reminiscent of other birds. The
extensor metacarpi radialis is a small, weak mus-
cle showing no indication of a division. Its tendon
fuses with that of the extensor longus alulae.
These two muscles act as extensors of the wrist,
counteracting the powerful flexor, the ulnimeta-
carpalis dorsalis, of the wrist.
Three muscles arising from the carpometacar-
pus control flexion and extension of the phalan-
ges. Extension is mediated by the very weak
abductor digiti majoris and interosseus ventralis
muscles. Flexion is the function of the strong
flexor digiti minoris.
The arrangement of the muscles of the leg is
less characteristic than that of the wing. Gervate
and Alix (1877:465) and Watson (1883:137) per-
ceived it as being similar to the arrangement that
characterizes the palmipedes (swimming birds) in
general. There are a number of deviations from
the arrangement found in these birds. The simi-
larities can be accounted for by adaptations to
similar modes of life. The iliotrochantericus cran-
ialis and iliotrochantericus medius are fused. In
penguins the iliofemoralis externus is very weak
and fused to the iliotrochantericus caudalis except
at the extreme distal end. This muscle is absent
in Podiceps, but present in most other swimming
birds, such as Gavia, Sula, and Chen (Hudson,
1937:13). The ambiens is a very strong, broad
muscle approaching the condition reported by
Hudson (1937:15) for Gavia. It is also well devel-
oped in other swimming birds but is absent in
grebes (Watson, 1883:129). The caudal part of
the iliotibialis is absent in penguins, but shows a
NUMBER 341 27
wide range of variation among other groups of
swimming birds. The caudo-ilio-femoralis is well
developed in all penguins, and both parts are
present. The insertion of this muscle is far distal
on the femur. The absence of the caudal part of
the iliotibialis leaves the iliofibularis uncovered
superficially.
A slip of muscle from the external oblique
inserts on an extensive area of the caudal border
of the flexor cruris medialis, an arrangement
found in no other group of birds. The flexor cruris
medialis shares a common insertion with the
flexor cruris lateralis. The insertion is by means
of a fleshy sheet medially and tendinous sheet on
the lateral side. The accessory flexor cruris later-
alis is absent in all penguins.
The weak condition of the short muscles of the
hallux and the delicate nature of the tendon from
the flexor hallucis longus are most likely related
to the vestigial nature of the hallux. The flexor
hallucis brevis is absent in most penguins exam-
ined. It is present in only five of the six specimens
of Pygoscelis. It has, however, been described in
Aptenodytes patagonicus (Reid, 1835:145) and Eu-
dyptes chrysolophus (Gervais and Alix, 1877:461).
Watson (1883:126) was unable to find any trace
of this muscle in the penguins he examined.
The absence of the adductor digiti II and weak
condition of the lumbricalis are also specialized
features of the leg myology of penguins.
Data in the present study were treated numer-
ically by two methods, cumulative scores of dif-
ference using weighted data and correlation coef-
ficients giving equal weight to all characters. The
two methods give closely parallel results. This is
evident in most interspecific and intergeneric
comparisons. Low scores of difference are usually
associated with high positive correlation coeffi-
cients and high scores with high negative corre-
lation coefficients.
In comparing various taxa, wing scores are
usually larger than leg scores. The mean for all
wing scores is 15.46 points and of leg scores 11.39
points. Only in the genus Eudyptes, does the mean
score for the leg exceed the wing score: 8.97 for
the legs compared to 8.10 for the wings. Many
other groups of birds show just the opposite, the
wings being least variable, e.g., in Galliformes
(Hudson and Lanzillotti, 1964), Lari and Alcae
(Hudson et al., 1969), Ciconiiformes (Vanden
Berge, 1970), Strigiformes and Caprimulgiformes
(Hoff, 1966), and Tinamous (Hudson et al.,
1972). The greater difference in wings compared
to legs is not surprising in view of the great
modification of the wing for underwater propul-
sion and differences in absolute size in different
genera. In the largest penguins, Aptenodytes and
Pygoscelis, the latissimus dorsi cranialis and cau-
dalis have increased so tremendously in width
that their adjacent borders have fused. This nu-
merical comparison indicates that the antarctic-
subantarctic genera Aptenodytes and Pygoscelis ex-
hibit the least interspecific variation, suggesting
that species in these genera are very closely re-
lated. The two genera, although quite different,
are more closely related to each other than to
other genera, as Peters (1931:29-31) indicates by
placing Pygoscelis immediately after Aptenodytes;
they are not necessarily more primitive than other
genera as his classification indicates. They are
perhaps less "primitive," being very specialized
in structure and behavior to endure the severe
environment of the antarctic region. Most likely
these genera evolved from forms inhabiting tem-
perate regions. Fossil evidence (Simpson, 1971)
suggests that the Sphenisciformes evolved in tem-
perate regions and have moved into the more
inhospitable antarctic regions. Selective pressures
most likely limit the amount of variation possible,
thus accounting for the similarity between these
antarctic-subantarctic species.
All correlation coefficients are low, i.e., below
0.60. Correlation coefficients of 0.60 or higher are
generally used in biological work to indicate close
relationship between two entities; two specimens
of the same species would therefore be expected
to have a correlation coefficient of 0.60 or higher.
Conversely, as the coefficient approaches ? 1, en-
tities exhibit less similarity and hence a more
distant relationship. Low correlation coefficients
support the presently recognized genera.
Eudyptula m. minor and E. m. albosignata are very
28 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
similar to each other. The scores of difference for
the wings, however, are higher than might be
expected for subspecies so strongly correlated.
This discrepancy may be a reflection of the very
small sample used in this study.
Spheniscus is a rather heterogeneous assemblage,
though the species of Spheniscus clearly constitute
a definite group. Of the four species comprising
the genus, S. demersus and S. humboldti (0.47) and
S. humboldti and S. mendiculus (0.43) show the
strongest correlation. Spheniscus demersus and S.
mendiculus are somewhat less well correlated.
Spheniscus magellanicus is most different. The simi-
larity between Eudyptes chrysolophus schlegeli and S.
humboldti suggests the possibility that Spheniscus
represents a radiation of penguins from the Aus-
tralian-New Zealand area into the South Ameri-
can-South African area. The derivation of Eu-
dyptes from Spheniscus seems unlikely, since the
fossil record (Simpson, 1946) indicates that pen-
guins arose in the Australian-New Zealand area.
With myological data and geographical distri-
bution, it is possible to construct a tentative phy-
logeny of sphenisciform birds. In such a phylog-
eny (Figure 19) three main divisions may be
recognized: (1) Aptenodytes, Pygoscelis; (2) Eudyptes,
Megadyptes; and (3) Spheniscus. Eudyptula represents
a small division with similarities to both the
Spheniscus and Eudyptes assemblages. This is very
similar to the phylogeny devised by Zusi (1975)
based on osteology.
Separation of species within each division is
also possible (Figure 19). Of the Spheniscus group,
S. magellanicus is most different, having diverged
along a separate pathway. S. humboldti, S. demersus,
and S. mendiculus are relatively closely related.
Penguins of the Eudyptes-Megadyptes lineage show
greater divergence. Megadyptes has diverged sig-
nificantly from the early members of this group,
as has E. chrysolophus schlegeli. The remaining
members of this group, being somewhat more
closely related, have perhaps diverged more re-
cently or occupied habitats with similar selective
factors.
The antarctic-subantarctic assemblage is com-
posed of two distinct genera, Aptenodytes and Py-
goscelis. Within these genera, species exhibit rather
close affinities. A. forsteri and A. patagonicus share
a correlation of 0.54. P. papua shares a correlation
of 0.60 with P. antarctica and a correlation of 0.62
with P. adeliae. The last two species share a cor-
relation of only 0.56. These relationships suggest
that P. papua is closest to the original species of
Pygoscelis, while P. adeliae and P. antarctica have
diverged to a greater degree.
Appendix
Interesting Features of the Appendicular Muscles
The following list considers the myological features of appendicular muscles
that show important differences among various groups of birds. Muscles
discussed in the text but not listed here exhibit no unusual modification in
penguins. List is arranged in the same order as the muscles are discussed in
the text.
MUSCLES OF THE PECTORAL APPENDAGE
LATISSIMUS DORSI CRANIALIS. Accessory slip from cranial edge
of triceps scapularis present in Aptenotfytes and Pygoscelis;
absent in other genera.
LATISSIMUS DORSI CAUDALIS. Arises from thoracic ribs in
penguins. Additional origin from spinous processes in
AptenodyUs and Pygoscelis.
LATISSIMUS DORSI METAPATAGIAUS. Extreme intergeneric var-
iation in width. Insertion on skin along lateral line of the
trunk instead of near the humeral feather tract as in most
birds.
SERRATUS SUPERFICIALIS CRANIALIS. TWO fleshy fascicles. Very
extensive insertion on the scapula.
SERRATUS SUPERFICIALIS METAPATAGIAUS. Absent in all pen-
guins.
SCAPULOHUMERALIS CRANIALIS. Absent in all penguins .
PECTORALJS PARS SUBCUTANEA ABDOMINAUS. Cranial part pre-
sent and very large; caudal part absent.
SUPRACORACOIDEUS. Very well developed in relation to the
pectoralis thoracica.
CORACOBRACHIALIS CRANIALIS. A very weak (vestigial) mus-
cle; not previously described for penguins.
SUBCORACOIDEUS. Belly large, single.
SUBSCAPULARIS, CAPUT LATERALE. Very large, much larger
than caput mediate; caput mediate has origin from cora-
coid, clavicle, and adjacent scapula (?? cranial head of
subcoracoideus, Hudson, et al., 1969:464).
PROPATAGIAUS. Belly single, tendon extends length of wing
and contributes to alar aponeurosis.
DELTOIDEUS MAJOR. A very weak, flat, usually triangular
muscle in penguins.
DELTOIDEUS MINOR. Short head very small and weak; long
head large, not connected to supracoracoideus.
TRICEPS SCAPULARIS. TWO distinct heads of origin, one from
clavicle and acromial process of scapula, other from lateral
border of scapular shaft.
TRICEPS HUMERALIS. TWO heads of origin, one from the
pneumatic fossa, the other from about the distal 0.60 of
the caudal border of the humeral shaft.
BICEPS BRACHII. Generally absent in penguins; rarely, a
vestigial biceps is present.
EXPANSOR SECUNDARIORUM. Absent in all penguins.
BRACHIALIS. Inserts on proximal end of radius instead of on
ulna as in other birds.
PRONATOR SUPERFICIALIS. Absent in all penguins.
PRONATOR PROFUNDUS. Absent in all penguins.
ENTEPICONDYLO-ULNARIS. Absent in all penguins.
FLEXOR CARPI ULNARIS. Represented by a tendon in all
penguins.
FLEXOR DIGITORUM SUPERFICIALIS. Represented by a single
tendon in all penguins.
ULNIMETACARPALIS VENTRAUS. Absent in penguins, except as
an infrequent vestige in less than one-sixth of the speci-
mens examined.
EXTENSOR METACARPI RADIALJS. Belly small, weak, single.
SupwATOR. A very small, weak, fan-shaped muscle, inserts
on dorsal surface of radius.
EXTENSOR DIGITORUM COMMUNIS. Represented by a tendinous
band in penguins.
EXTENSOR METACARPI ULNARIS. Represented by a tendon in
all penguins; insertion usually on the major metacarpal.
ECTEPICONDYLO-ULNARIS. Replaced by a tendon, occasionally
a few fleshy fibers are present.
EXTENSOR LONGUS ALULAE. TWO fleshy heads of origin; ten-
don fused with extensor metacarpi radialis at wrists; radial
head absent in most Evufyptula wings.
EXTENSOR LONGUS DIGITI MAJORIS. Represented by a tendon
in all penguins; no distal head.
ULNIMETACARPALIS DORSAUS. Belly large, single.
ABDUCTOR ALULAE. Absent in all penguins.
FLEXOR ALULAE. Absent in all penguins.
ADDUCTOR ALULAE. Absent in all penguins.
EXTENSOR BREVIS ALULAE. Absent in all penguins.
ABDUCTOR DIGITI MAJORIS. Flat, weak; arises from the ventral
surface of the major metacarpal near cranial border.
29
30 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
INTEROSSEUS DORSALIS. Represented by a tendon in all pen-
guins.
FLEXOR DIGITI MINORIS. Belly well developed.
MUSCLES OF THE PELVIC APPENDAGE
ILIOTROCHANTERICUS CRANIALIS. Fused to iliotrochantericus
medius, the two muscles are barely distinguishable.
ILIOFEMORALIS EXTERNUS. Very weak; fused to iliotrochanter-
icus caudalis except extreme distal end of belly and tendon
of insertion; origin cranial to acetabulum.
AMBIENS. Belly very strong; inserts on the tendon of origin of
the cranial head of the perforated flexors.
ILIOTIBIALIS. Cranial part present; postacetabular portion
absent.
FEMOROTIBIALIS EXTERNUS. Completely separate in some
taxa; partially fused with the femorotibialis medius in
others; not separable in others.
FEMOROTIBIALIS MEDIUS. Origin partly covers common inser-
tion of iliotrochantericus cranialis and iliotrochantericus
medius.
FEMOROTIBIALIS INTERNUS. NO division of belly distally.
CAUDO-ILIO-FEMORALIS. M. caudofemoralis and M. iliofe-
moralis well developed; insertion far distal on femur.
FLEXOR CRURIS LATERALIS. Origin fleshy from transverse proc-
esses of about the first six free caudal vertebrae, no attach-
ment to ilium; accessory portion absent in all penguins.
FLEXOR CRURIS MEDIALIS. Insertion fleshy, in common with
flexor cruris lateralis; a tendinous sheet on the lateral side
of common insertion (on medial side in a more typical
bird, e.g., Gallus).
ILIOFIBULARIS. Belly not covered by iliotibialis; tendon of
insertion appears to be composed of two or more fibrous
fascicles fused together and compressed laterally.
ISCHIOFEMORALIS. Extensive origin including much of ventral
edge of the caudal part of the dorsolateral crest of the
ilium.
OBTURATORIUS MEDIALIS. Insertion in common with obtura-
torius lateralis on caudal border of femoral trochanter.
OBTURATORIUS LATERALIS. Single; origin nearly surrounds
foramen obturatorium.
PUBO-ISCHIO-FEMORALIS. Belly clearly divided into lateral
and medial heads, especially cranially.
TIBIALIS CRANIALIS. Tendon of insertion sends a very weak
branch laterally to metatarsus II.
EXTENSOR DIGITORUM LONGUS. Tendon forms aponeurotic
triangle opposite tarsometatarsus.
FIBULARIS LONGUS. Tendon sends branch along lateral side
of metatarsus IV and digit IV, ending on the penultimate
phalanx.
FIBULARIS BREVIS. An extremely weak muscle.
GASTROCNEMIUS. All three heads well developed; tendon
branches near the proximal end of the tarsometatarsus;
does not ensheath flexor tendons over tarsometatarsus;
pars intermedia strongly fused to pubo-ischio-femoralis.
M U S C L E S O F T H E F L E X O R T E N D O N S
FLEXOR PERFORANS ET PERFORATUS DIGITI II. Very broad
proximally.
FLEXOR PERFORANS ET PERFORATUS DIGITI III. No vinculum
between tendon of flexor perforans et perforatus digiti III
and flexor perforatus digiti III; belly notched slightly
proximal with a tendinous sheet extending between these
two parts.
FLEXOR PERFORATUS DIGITI IV. The tendon of insertion shows
four patterns of branching and attachment in different
taxa.
FLEXOR HALLUCIS LONGUS. The tendon trifurcates opposite
the tarsometatarsus, the three short branches fuse to those
of the flexor digitorum longus; a fibrous connection on the
medial side resembles a vestigial vinculum; branch to
hallux very delicate, ending on the ungual phalanx; belly
large in relation to size of hallux.
POPLITEUS. Muscle fleshy throughout.
EXTENSOR HALLUCIS LONGUS. Very weak; origin from rudi-
mentary metatarsus and phalanx 1, tendon strongly at-
tached to length of phalanx 1, ending on ungual phalanx.
EXTENSOR PROPRIUS DIGITI III. Absent in all penguins.
EXTENSOR BREVIS DIGITI IV. Tendon does not pass through a
bony canal.
FLEXOR HALLUCIS BREVIS. Absent in Aptenodytes, Eudyptes,
Megadyptes, Eudyptula, and Spheniscus; present in five of six
specimens of Fygoscelis examined, minute.
ADDUCTOR DIGITI II. Absent in penguins.
LUMBRICALIS. Weak when present; most specimens have a
very small vestige of this muscle.
ADDUCTOR DIGITI IV. Absent in all penguins.
Literature Cited
Baumel, J. J., A. S. King, A. M. Lucas, J. E. Breazile, and
H. E. Evans, editors
1979. Nomina Anatomica Avium. 637 pages. London: Aca-
demic Press.
Beddard. F. E.
1898. The Structure and Classification of Birds. 548 pages.
New York: Longmans, Green, and Co.
Falla, R. A., and J.-L. Mougin
1979. Sphenisciformes. In E. Mayr and G. W. Cottrell,
editors, Check-list of Birds of the World, second edi-
tion, 1:121-134. Cambridge, Mass.: Museum of
Comparative Zoology.
Filhol, H.
1885. Observations anatomiques, relative a diverses es-
peces de Manchots. Memoires sur la Passage de Venus,
3 (2):35-339.
Gadow, H., and E. Selenka
1891. Vogel, 1: Anatomischer Theil. In H.G. Bronn, Die
Klassen und Ordnungen des Their-Reichs., 6(4): 1008
pages. Leipzig.
Garrod, A. H.
1873. On Certain Muscles of the Thigh of Birds, and
Their Value in Classification. Proceedings of the
Zoological Society of London, 1:626-644.
George, J. C , and A. J. Berger
1966. Avian Myology. 500 pages. New York: Academic
Press.
Gervais, P., and E. Alix
1877. Osteologie et Myologie des Manchots. Journal de
Zoologie (Paris), 6:424-472
Hoff, K. M.
1966. A Comparative Study of the Appendicular Mus-
cles of Strigiformes and Caprimulgiformes. Ph.D.
dissertation, Washington State University, Pull-
man.
Hudson, G. E.
1937. Studies on the Muscles of the Pelvic Appendage
in Birds. American Midland Naturalist, 18:1-108.
Hudson, G. E., and P. J. Lanzillotti
1964. Muscles of the Pectoral Limb in Galliform Birds.
American Midland Naturalist, 7 1 : 1 - 1 1 3 .
Hudson, G. E., R. A. Parker, J. Vanden Berge, and P. J.
Lanzillotti
1966. A Numerical Analysis of the Modifications of the
Appendicular Muscles in Various Genera of Gal-
linaceous Birds. American Midland Naturalist, 76:1-
73.
Hudson, G. E., K. M. Hoff, J. Vanden Berge, and E. C.
Trivette
1969. A Numerical Study of the Wing and Leg Muscles
of Lari and Alcae. Ibis, 111:459-524.
Hudson, G. E., D. O. Schreiweis, S. Y. C. Wang, and D. A.
Lancaster
1972. A Numerical Study of the Wing and Leg Muscles
of Tinamous (Tinamidae). Northwest Science, 46:
207-255.
Meckel, J. F.
1828. System der vergleichenden Anatomic Halle, 3:
289-392.
Peters, J. L.
1931. Check List of the Birds of the World. Volume 1.
Cambridge: Harvard University Press.
ReidJ.
1835. Anatomical Description of the Patagonian Pen-
guin (Aptenodytes patachonica). Proceedings of the Zoo-
logical Society of London, 132-148.
Schoepss, C. G.
1829. Beschreibung der Flugelmuskeln der Vogel. In
J. F. Meckel, Archiv fur Anatomic und Physiologic, 72 -
176. Leipzig.
Sibley, C. G., and J. E. Ahlquist
1972. A Comparative Study of the Egg-White Proteins
of Non-Passerine Birds. Peabody Museum of Natural
History Bulletin, 39: 276 pages, 37 figures.
Simpson, G. G.
1946. Fossil Penguins. Bulletin of the American Museum of
Natural History, 87:9-99.
1971. A Review of the Pre-Pliocene Penguins of New
Zealand. Bulletin of the American Museum of Natural
History, 114:319-378.
1975. Fossil Penguins. In B. Stonehouse, editor, Biology of
Penguins, pages 19-41. New York: Macmillan Pub-
lishing Company.
Vanden Berge, J. C.
1970. A Comparative Study of the Appendicular Mus-
culature of the Order Ciconiiformes. American Mid-
land Naturalist, 84:289-364.
Watson, M.
1883. Report on the Anatomy of the Spheniscidae Col-
lected during the Voyage of H.M.S. Challenger. In
Report on the Scientific Results of the Voyage of H. M.S.
Challenger during the Years 1873-76: Zoology, 7(18):
244 pages. Edinburgh: Neil and Company.
Zusi, R.
1975. An Interpretation of Skull Structure in Penguins.
In B. Stonehouse, editor. Biology of Penguins, pages
59-84. New York: Macmillan Publishing Com-
pany.
31

Abbreviations on Illustrations
Arabic numbers and lower case letters on illustrations denote tendons that
have been cut; each number or letter corresponds to the superscript of
corresponding muscle; roman numeral denotes number of digit or muscle
related to that digit.
ABD. DIG. II
ABD. DIG. IV
ABD. DIG. MAJ.
BRACH.
CAUD. FEM.
COR. BRA. CAUD.
COR. BRA. CRAN.
COS. STER. MAJ.
COS. STER. MIN.
DELT. MAJ.
DELT. MIN.
DEPR. CAUDAE
ECT.-ULN.
E. DIG. COM.
E. LON. AL.
E. LON. DIG. MAJ.
E. META. RAD.
E. META. UL.
EXT. BREV. D. III.
EXT. BREV. D. IV
EXT. DIG. L.
EXT. HAL. L.
F. CAR. UL.
F. DIG. L.
F. DIG. MIN.
F. DIG. PROF.
F. DIG. SUP.
FEM. TIB. EXT.
FEM. TIB. INT.
FEM. TIB. MED.
F. HAL. L.
FIB. BREV.
FIB. LONG.
FL. CR. LAT.
FL. CR. MED.
FLEX. PER. D. II
FLEX. PER. D. HI
FLEX. PER. D. IV
F. P. ET P. D. II
F. P. ET P. D. Ill
GAS.
GAS. (P. INT.)
Abductor digiti II
Abductor digiti IV
Abductor digiti majoris
Brachialis
Caudofemoralis
Coracobrachialis caudalis
Coracobrachialis cranialis
Costosternalis majoris
Costosternalis minoris
Deltoideus major
Deltoideus minor
Depressor caudae
Ectepicondylo-ulnaris
Extensor digitorum communis
Extensor longus alulae
Extensor longus digiti majoris
Extensor metacarpi radialis
Extensor metacarpi ulnaris
Extensor brevis digiti HI
Extensor brevis digiti IV
Extensor digitorum longus
Extensor hallucis longus
Flexor carpi ulnaris
Flexor digitorum longus
Flexor digiti minoris
Flexor digitorum profundus
Flexor digitorum superficialis
Femorotibialis externus
Femorotibialis internus
Femorotibialis medius
Flexor hallucis longus
Fibularis brevis
Fibularis longus
Flexor cruris lateralis
Flexor cruris medialis
Flexor perforatus digiti II
Flexor perforatus digiti III
Flexor perforatus digiti IV
Flexor perforans et perforatus
digiti II
Flexor perforans et perforatus
digiti HI
Gastrocnemius
Gastrocnemius pars intermedia
GAS. (P. LAT.)
GAS. (P. MED.)
IL. FEM.
ILFEM. EXT.
ILFEM. INT.
ILFIB.
IL. TIB.
ILTIB. CRAN.
IL. TROC. CAUD.
IL. TROC. CRAN.
IL. TROC. MED.
INT. COS. EXT.
INT. COS. INT.
INT. DOR.
INT. VEN.
ISCH. FEM.
LAT. DOR. CAUD.
LAT. DOR. CRAN.
LAT. DOR. MET.
OBT. LAT.
OBT. MED.
PECT. SUB. ABD.
PECT. THO.
PLAN.
PROPAT.
PUB.-IS.-FEM.
RHOM. PRO.
RHOM. SUP.
SCAP. HUM. CAUD.
SERR. PRO.
SERR. SUP. CAUD.
SERR. SUP. CRAN.
STER. COR.
STER. TRACH.
SUBCOR.
SUBSCP. (CAP. LAT.)
SUBSCP. (CAP. MED.)
SUP. COR.
SUPIN.
TIB. CRAN.
TRI. HUM.
TRI. SCAP.
UL. META. DOR.
Gastrocnemius pars lateralis
Gastrocnemius pars medialis
Iliofemoralis
Iliofemoralis externus
Iliofemoralis internus
Iliofibularis
Iliotibialis
Iliotibialis cranialis
Iliotrochantericus caudalis
Iliotrochantericus cranialis
Iliotrochantericus medius
Intercostalis externus
Intercostalis internus
Interosseus dorsalis
Interosseus ventralis
Ischiofemoralis
Latissimus dorsi caudalis
Latissimus dorsi cranialis
Latissimus dorsi metapatagialis
Obturatorius lateralis
Obturatorius medialis
Pectoralis pars subcutanea
abdominalis
Pectoralis thoracica
Plantaris
Propatagialis
Pubo-ischic-femoralis
Rhomboideus profundus
Rhomboideus superficialis
Scapulohumeralis caudalis
Serratus profundus
Serratus superficialis caudalis
Serratus superficialis cranialis
Sternocoracoideus
Stemotrachialis
Subcoracoideus
Subscapularis caput laterale
Subscapularis caput mediate
Supracoracoideus
Supinator
Tibialis cranialis
Triceps humeralis
Triceps scapular is
Ulnimetacarpalis dorsalis
33
34 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
RHOM. SUP
LAT. DOR. CRAN
PAT.
T R I . SCAP. (DOR.)
LT. MAJ.
,SUP. COR.
E. META. RAD.
LAT. DOR. M E T . _
ILTIB. CRAN
E. LON. AL.
 E ( N ? TA.UL.
. DIG. COM.
NT. DOR.
FIGURE 1.?Eudyptes pachyrhynchus, dorsal view of superficial muscles of the right wing.
DELT. MAJ.
PROPAT,.
TRI. SCAP. (DOR.
TRI. SCAP. (VEN.
LAT. DOR. CRAN
SIBSCP. (CAP. LAT.]
PHOM. SUP
SCAP. HIM. CAUD
RHOM. PRO
MIN
IL. TROC. CAUD
FIGURE 2.?Eudyptes pachyrhynchus, dorsal view of second layer of muscles of the right wing.
NUMBER 341 35
PROPAT.
T R I . SCAP, (DOR.).
COR, BRA. CAUD,
SUBSCP. (CAP. LAT.)
RHOM. PRO.
SCAP. HUM. CAUD
.PECT. THO.
,DELT. MIN.
.SUP. COR.
T R I . HUM. (VEN.)
UPIN.
ECT.-ULN.
E. LON. AL.
E. META. RAD.
. DIG. COM.
T R I . HUM. (DOR.)
. THO.
LON. DIG. MAJ.
UL. META. DOR,
FIGURE 3.?Eudyptes pachyrhynchus, dorsal view of deepest muscles of the right wing.
PECT. THO.
/ R I . HUM. (VEN.)
TRI. HUM. (DOR.)
. DIG. MIN.
FIGURE 4.?Eudyptes pachyrhynchus, ventral view of superficial muscles of the left wing.
36 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
PECT. THO,
SUBSCP. (CAP. LAT.)
COR. BRA. CAUD
SUP. COR. -
.COR. BRA. CRAN.
,PECT. THO.
JRI. HUM. (VEN.)
tl, HUM. (DOR.)
F. DIG. PROF.
. DIG. MAJ.
INT. VEN.
FIGURE 5.?Eudyptes pachyrhynchus, ventral view of second layer of muscles of the left wing.
PECT. THO
SUBSCP. (CAP. LAT.)
DELT, MIN. (VEN.
COR. BRA. CAUD.
BRA. CRAN.
,TRI. HUM, (VEN.)
I. HUM. (DOR.)
F. DIG. PROF.
FIGURE 6.?Eudyptes pachyrhynchus, ventral view of deepest muscles of the thorax.
NUMBER 341 37
SCAP, HUM. CAUD.
. SUP. CRAN.
SERR. SUP. CAUD
INT. COS. EXT,
INT. COS. INT
COS. STER. MAJ.
COS. STER. MIN.
STER. TRACH,
FIGURE 7.?Eudyptes pachyrhynchus, medial view of deep muscles of the thorax.
SCAPULA
FIBROUS PULLEY
LAT. DOR. CRAN
HWERUS
LAT. DOR.
FIGURE 8.?EtufypUs pachyrhynchus, dorsal view of fibrous pul-
ley and insertion of the latissimus dorsi cranialis and cau-
dalis.
38 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
ILTIB. CRAN
IL. TIB.
PUB.- IS. -FEM
EXT. DIG. L . e
IL FEM.
ILFIB.
FL. CR. LAT,
FEM.
IV III
FIGURE 9.?Eudyptes pachyrhynchus, lateral view of superficial muscles of the left leg (caudal
part of abdomen and most of tail muscles are not shown).
NUMBER 341 39
IL TROC. CAUD,
IL. TROC. CRAN, AND MED,
AMBIENS.
FEM. TIB. MED
PUB. - IS . -FEM.
F. HAL. L.
. FEM.
I L F I B . a
FLEX. PER. D . I l l
F . D I G . L
L. CR. LAT.b
FIGURE 10.?Eudyptes pachyrhynchus, lateral view of a second layer of muscles of the left leg.
40 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
I L . TROC. CAUD,
IL . TROC. CRAN. AND MED
PUB.-IS.-FEM
FEM. T I B . MED
FLEX. PER. D. I
F
FLEX.
AMBIEN
. HAL.
PER.
GAS.
FLEX.
S
L.
D.
(P.
38
\\C
MED.
PER. D.
T IB .
F.
H
i f "
CRAN-
DIG. L
\, LONG
FIB. BREV.
ILFEM. EXT.
FIGURE 11.?Eudyptes pachyrhynchus, lateral view of a third layer of muscles of the left leg.
NUMBER 341 41
I L . TROC. CRAN. AND MED
FEM. T I B . EXT.
ANT. ORIGIN OF
PERFORATED FLEXORS
EXT. DIG. L
F. HAL. L
OBT. MED. AND LAT.
PUB.- IS. -FEM.
FIGURE 12.?Eudyptes pachyrhynchus, lateral view of deepest muscles of the left leg.
42 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
OBT. MED
DEPR. CAUDAE
L. TIB.
LTIB. CRAN,
FEM. T IB . MED,
AMBIENS
FEM. T IB . INT.
PUB.-IS.-FEM.
U P FROM EXT
EXT. OBL.
II
III
FIGURE 13.?Eudyptes pachyrhynchus, medial view of superficial muscles of the left leg.
NUMBER 341
FEM. T IB . MED.
ILFEM. INT.
FEM. T IB. INT'.
F. HAL. L.
PLAN.
FLEX. PER, D. I I
F. DIG. L
43
FL, CR. MED.
ABD. DIG. II
NOTCH FOR
AMBIENS TENDON
IV
FIGURE 14.?Eudyptes pachyrhynchus, medial view of deeper
muscles of the left leg.
ABD, DIG. I
EXT. HAL. L.
J I B . CRAN.
EXT. BREV. D. IV
EXT. BREV. D. I l l
: _ F I B . LONG.
I B . CRAN.
. BREV. D. IV
EXT. DIG. L . a
E X T . B R E V . D . I l l
II
IV
ICURE 15.?Eudyptes pachyrhynchus, dorsal view of superficial
muscles of the left foot.
ABD. DIG. IV
ABD. DIG. I I
F. HAL. L.
ICURE 16.?Eudyptes pachyrhynchus, cranial view of deep :IGURE 17.?Eudyptes pachyrhynchus, caudal view of tarsus
muscles of the left tarsus. showing short foot muscles.
44 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
F. DIG. L.a
FIB, LONG
ABD. DIG. IV
FLEX. PER. D. I l l
FLEX. PER. D. IV -~T
HAL. L.b
ABD. DIG. I I
P. ET P. D. I I I C
. P. ET P. D. I I d
FLEX. PER. D. I I
II
FIGURE 18.?Eudyptes pachyrhynchus, plantar view of left foot
with most tendons displaced.
S. MAGELLAMCUS
S-KMERSUS
5 HUMBOLOTI
6 MENUCULUS
EU MINOR
M. ANTIPOOES
E. CHRYSOLOPHUS
E. CHRYSOCOME
E. PACHYRHYNCHUS
R ANTARCTICA
P. AOELIAE
R PAPUA
A. FORSTERI
A PATA60MCUS
FIGURE 19.?Proposed phylogeny of the Spheniscidae (Sphen-
iscus, Eudyptula, Megadyptes, Eudyptes, JPygoscelis, and Apteno-
dytes) based on total scores of difference between species and
genera derived from numerical analysis.
Index to Muscles
(Pages of primary descriptions in italics.)
Abductor alulae, 14, 29
Abductor digiti II, 25
Abductor digiti IV, 25
Abductor digiti majoris, 13, 26, 29
Adductor alulae, 14, 29
Adductor digiti II, 25, 27, 30
Adductor digiti IV, 25, 30
Ambiens, 16, 26, 30
Biceps brachii, 9, 26, 29
Biceps femoris, 16
Brachialis, 9, 11,26,29
Caudofemoralis, 17
Caudo-ilio-femoralis, 17, 27, 30
Coracobrachialis caudalis, 5, 6
Coracobrachialis cranialis, 6, 29
Deltoideus major, 6, 7, 8, 26, 29
Deltoideus minor, 6, 8, 26, 29
Ectepicondylo-ulnaris, 12, 29
Entepicondylo-ulnaris, 14, 29
Expansor secundariorum, 14, 26, 29
Extensor brevis alulae, 14, 29
Extensor brevis digiti III, 24
Extensor brevis digiti IV, 25, 30
Extensor digitorum communis, / / , 12, 13, 29
Extensor digitorum longus, 20, 30
Extensor hallucis longus 24, 30
Extensor longus alulae, 11, 12, 26, 29
Extensor longus digiti majoris, 11, 12,29
Extensor metacarpi radialis, / / , 12, 26, 29
Extensor metacarpi ulnaris, 12, 29
Extensor proprius digiti III, 25, 30
Femorotibialis externus, 16, 30
Femorotibialis internus, 16, 17, 30
Femorotibialis medius, 15, 17, 30
Fibularis brevis, 20, 30
Fibularis longus, 20, 22, 23, 30
Flexor alulae, 14, 29
Flexor carpi ulnaris, 10, 29
Flexor cruris lateralis, 18, 27, 30
Flexor cruris medialis, 18, 27, 30
Flexor digiti minoris (Flexor digiti HI), 14, 26, 30
Flexor digitorum longus, 21, 22, 23, 24
Flexor digitorum profundus, 10
Flexor digitorum superficial^ 10, 29
Flexor hallucis brevis, 25, 27, 30
Flexor hallucis longus, 21, 23, 27, 30
Flexor perforans et perforatus digiti II, 21, 22, 30
Flexor perforans et perforatus digiti III, 21, 22, 23, 30
Flexor perforatus digiti II, 21, 22, 23
Flexor perforatus digiti III, 20, 21, 22, 23
Flexor perforatus digiti IV, 21, 22, 23, 30
Gastrocnemius, 18, 19, 21, 22, 30
Iliofemoralis, 17
Iliofemoralis externus, 14, 15, 26, 30
Iliofemoralis internus, 16, 17
Iliofibularis, 18, 22, 23, 27, 30
Iliotibialis, 16, 18, 26, 30
Iliotibialis cranialis, 16
Iliotrochantericus caudalis, 14, 15, 26
Iliotrochantericus cranialis, 15, 17, 19, 26, 30
Iliotrochantericus medius, 15, 16, 17, 19, 26
Interosseus dorsalis, 13, 30
Interosseus ventral is, 14, 26
Ischiofemoralis, 15, 18, 19, 30
Latissimus dorsi, 2, 8, 26
Latissimus dorsi caudalis, 2, 3, 8, 27, 29
Latissimus dorsi cranialis, 2, 3, 27, 29
Latissimus dorsi matapatagialis, 2, 3, 26, 29
Lumbricalis, 25, 27, 30
Obturatorius lateralis, 19, 30
Obturatorius medialis, 19, 30
Pectoraiis, 5
Pectoraiis pars subcutanea abdominalis, 5, 6, 29
Pectoraiis propatagialis, 5
Pectoraiis thoracica, 5, 6, 9, 26
Plantaris, 21
Popliteus, 24, 30
Pronator profundus, 14, 26, 29
Pronator superficial is, 14, 26, 29
Propatagialis, 5, 7, 8, 9, 10, 11, 26, 29
Pubo-ischio-femoralis, 19, 21, 30
Rhomboideus profundus, 3
Rhomboideus superficialis, 3, 4
Scapulohumeralis caudalis, 5
Scapulohumeralis cranialis, 14, 26, 29
Serratus profundus, 4
Serratus superficialis caudalis, 4, 5
Serratus superficialis cranialis, 4, 7, 29
Serratus superficialis metapatagialis, 14, 26, 29
Sternocoracoideus, 6
Subcoracoideus, 7, 29
Subscapularis, 7
Subscapularis caput laterale, 4, 7, 29
Subcapularis caput mediate, 4, 7
45
46 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
Supinator, // , 29
Supracoracoideus, 5, 6, 26, 29
Tensor patagii longus, 7, 8
Tibialis cranialis, 19, 20, 21, 30
Triceps brachii, 8, 26
Triceps humeralis, 8, 9, 26, 29
Triceps scapularis, 3, 8, 9, 26, 29
Ulnimetacarpalis dorsalis, 13, 26, 29
Ulnimetacarpalis ventralis, 10, 29


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