PROC. ENTOMOL. SOC. WASH.
115(2), 2013, pp. 173?181
PTENIDIUM KISHENEHNICUM (COLEOPTERA: PTILIIDAE), A NEW
FOSSIL DESCRIBED FROM THE KISHENEHN OIL SHALES, WITH
A CHECKLIST OF PREVIOUSLY KNOWN FOSSIL PTILIIDS
FLOYD W. SHOCKLEY AND DALE GREENWALT
(FWS) Department of Entomology, National Museum of Natural History,
Smithsonian Institution, P.O. Box 37012, MRC?165, Washington, DC 20013?7012
(e-mail: ShockleyF@si.edu); (DG) Department of Paleobiology, National Museum of
Natural History, Smithsonian Institution, P.O. Box 37012, MRC?121, Washington,
DC 20013?7012 (e-mail: GreenwaltD@si.edu)
Abstract.?Ptenidium kishenehnicum Shockley and Greenwalt, a new species
of feather-winged beetle (Coleoptera: Ptiliidae), is described from 46 million year
old Kishenehn oil shales in Montana, USA. This compression fossil is the ?rst beetle
species to be described from this formation. A checklist of known fossils and their
ages is provided.
Key Words: compression fossil, feather-winged beetles, fossil beetles, taxonomy,
paleoentomology
DOI: 10.4289/0013-8797.115.2.173
The feather-winged beetles (Coleoptera:
Ptiliidae), while worldwide in their dis-
tribution, constitute a relatively small
family, with approximately 635 described
species (Grebennikov 2009). They are
unique in that they are among the small-
est insects known, with body lengths of
400 mm or less reported, and with fe-
males having a single ovary?the insect
can accommodate only one maturing egg
at a given time (Polilov 2005). The small
size of the Ptiliidae may also be re-
sponsible for other unusual character-
istics, such as complete lack of a heart
(Grebennikov 2008) and the extremely
small wing membranes, often 20 times
greater in length than width, with nu-
merous long setae attached to their mar-
ginal edges that contribute the majority of
the wing?s surface area (Horridge 1956,
Grebennikov 2008).
The fossil record for Ptiliidae is better
than one might expect given the numbers
of described extant species and the bee-
tles? small physical size. Several major
catalogs of fossil beetles (Klebs 1910,
Spahr 1981, Carpenter 1992) have in-
cluded Ptiliidae. Ptiliids have been found
in amber from the Baltic, the Dominican
Republic, Lebanon, Rovno, Myanmar and
Mexico (Table 1). In fact, ptiliids have
been reported to make up 11% of all
Coleoptera in the American Museum of
Natural History collection of Myanmar
amber (Grimaldi et al. 2002). Isolated
ptiliid elytra have also been found in
Holocene, Pleistocene and Pliocene de-
posits (Matthews 1977, Matthews and
Telka 1997). Despite the relatively large
number of reports of fossil ptiliids, only
?ve species of Ptiliidae have been de-
scribed (Table 1). Compression fossils
of Ptiliidae are even more rare, with only
a single such fossil described (Statz and
Horion 1937). The small number of fossil
species is not only a result of their ex-
tremely small size, but also the result of
a reliance on anatomical details rarely
preserved in fossilized specimens but re-
quired for ptiliid species identi?cation.
The oil shales of the Kishenehn For-
mation in northwestern Montana have re-
cently been shown to contain exquisitely
preserved insects with a bias for the pres-
ervation of very small insects (Greenwalt
et al. 2011). For example, six new species of
Mymaridae (Hymenoptera: Chalcidoidea),
the ?rst ever to be described from com-
pression fossils, were recently described
from the Kishenehn Formation (Huber and
Greenwalt 2011).
Although Constenius et al. (1989)
recorded two different beetle families,
Scarabaeidae and Chrysomelidae, from
the Kishenehn Formation, these speci-
mens were never formally described. We
herein describe the ptiliid fossil Ptenidium
kishenehnicum Shockley and Greenwalt,
new species, the ?rst species of any
Coleoptera to be described from the
Kishenehn oil shales and the ?rst fossil
ptiliid to be described from the New
World.
MATERIALS AND METHODS
The compression fossil described herein
is housed in the National Museum of
Natural History (NMNH). It was col-
lected in 2010 at the Constenius Spring
site along theMiddle Fork of the Flathead
River in northwestern Montana under the
auspices of USFS Permit HUN281. It was
collected from the middle sequence of
the Coal Creek member of the Kishenehn
Formation, which has been estimated to be
46.2 +/? 0.4 Ma by 40Ar/39Ar analysis and
Table 1. References to fossils of Ptiliidae Erichson, 1845, with approximate age of formations. Ages of formations
largely derived from Grimaldi and Engel (2005).
Taxon Reference(s) Fossil Type Age
Ptiliidae Poinar 1992, Poinar and Poinar 1999,
Wu 1996
Dominican amber 20?17 Ma
Ptiliidae Poinar 1992 Mexican amber 29.0?23.6 Ma
Ptiliidae Poinar and Poinar 2008 Lebanese amber 125 Ma
Ptiliidae Rasnitsyn and Ross 2000, Grimaldi
et al. 2002, Poinar and Poinar 2008
Burmese amber 95 Ma
Ptiliidae Helm 1896, Klebs 1910, Larsson 1978,
Kulicka and Slipinski 1996
Baltic amber 44 Ma
Acrotrichis sp. Matthews 1977 Disarticulated fragments 5.7 Ma
Acrotrichis sp. Matthews and Telka 1997 Disarticulated fragments 9.36 Ka
Acrotrichis sp. Matthews and Telka 1997 Disarticulated fragments 125 Ka
Acrotrichis sp. Matthews and Telka 1997 Disarticulated fragments 5.2?1.7 Ma
Micridium groehni Polilov and Perkovsky 2004 Baltic amber 44 Ma
Micridium sp. Matthews 1977 Disarticulated fragments 5.7 Ma
Microptilium geistautsi Dybas 1961 Baltic amber 44 Ma
Ptilium tertiarium Horion (in Statz and Horion) 1937 Compression 23.6?21.0 Ma
Ptilium sp. Polilov and Perkovsky 2004 Baltic amber 44 Ma
Ptilium sp. Polilov and Perkovsky 2004 Rovno amber 54.8?33.7 Ma
Ptinella oligocenica Parsons 1939 Baltic amber 44 Ma
Ptinella rovnoensis Polilov and Perkovsky 2004 Rovno amber 54.8?33.7 Ma
Ptenidium kishenehnicum Present paper Compression 46.2?43.5 Ma
Ptenidium sp. Klebs 1910, Handlirsch 1925,
Bachofen-Echt 1949, Polilov
and Perkovsky 2004
Baltic amber 44 Ma
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON174
43.5 +/? 4.9 Ma by ?ssion-track analysis
(Constenius et al. 1989, Constenius 1996).
An interesting feature of fossils re-
covered from this formation is that their
details are best seen when the shale is
wetted. The compression fossil was there-
fore immersed in 95% ethanol for exami-
nation and photography. The dorsal habitus
imagewas captured using a Canon EOS 7D
attached to a Visionary Digital Imaging
System (Visionary Digital?, Palmyra,
VA). Images were then montaged and
edited using Adobe Photoshop.
The following measurements were re-
corded as part of the description. Total
length (TL) was measured from the an-
terior margin of the head capsule to the
apex of the abdomen, and total width
(TW) was measured at the widest point
across the elytra. Head length (HL) was
measured at the midline from the anterior
to posterior margin of the head capsule,
and head width (HW) was measured at
the widest point across the head capsule.
Pronotal length (PL) was the length mea-
sured at the midline from the anterior to
posterior margin, and pronotal width (PW)
was measured at the widest point across
the pronotum. Elytron length (EL) was the
length measured from the anterior margin
to the apex along the suture, and elytron
width (EW) was measured at the widest
point across one elytron. Abdomen length
(AL) was measured at the midline from
the anterior margin of abdominal ventrite
1 to the apex of abdominal ventrite 6, and
abdomen width (AW) was measured at
the widest point across the abdomen.
RESULTS
Ptenidium kishenehnicum Shockley
and Greenwalt, new species
(Figs. 1?2)
Diagnosis.?This new species differs
markedly from the other five described
species of fossil ptiliids, known mostly
from amber. Its relative small size (0.65
mm) distinguishes it from Microptilium
gestautsi Dybas, Ptinella oligocoenica
Parsons, and Ptinella rovnoensis Polilov
and Perkovsky, which are all 0.80?0.91
mm in length. The large mesoscutellum
and the shape and sculpturing of the pro-
notum readily separates P. kishenehnicum
from Micridium groehni Polilov and
Perkovsky and Ptilium tertiarium Horion,
the only other species described from a
compression fossil.
Description.?Overall body shape elon-
gate oval, body widest across middle of
elytra. TL = 0.65 mm, TW = 0.35 mm.
Body coloration reddish-brown, head dark
brown, antennae lighter. Clypeus is dark
gray in appearance.
Fig. 1. Ptenidium kishenehnicum Shockley and
Greenwalt, new species. Scale bar = 0.1 mm.
VOLUME 115, NUMBER 2 175
Head: Head broadly oval, 1.4X as
broad as long, HL = 0.14 mm, HW =
0.20 mm. Partially obscured from above
by pronotum such that the anterior an-
gles approach the posterior margin of the
eyes. Antennal insertions fully exposed
(dif?cult to see on the left), positioned
medially on vertex near anteromedial
margin of eye. Eyes prominent, coarsely
faceted. Fronto-clypeal suture conspic-
uous due to discoloration of clypeus,
evenly arcuate between the antennal in-
sertions. Clypeus large and laterally lobed,
expanded apically (possibly an artifact
of compression), convex along anterior
margin. Mouthparts directed ventrally
and obscured dorsally by head capsule.
Antennae 11-segmented with loose
3-segmented club. Scape and pedicel
subequal in length, enlarged and barrel-
shaped; antennomere 3 smaller; anten-
nomeres 4?6 elongate and narrow, each
subequal in length to pedicel but only
0.5X as wide; antennomeres 7?8 signif-
icantly shorter and progressively wider
than preceding segments, bead-like in ap-
pearance; antennomeres 9?11 forming a
loose 3-segmented club, as long as pre-
ceding 4 segments combined; antennomeres
9?10 as long as wide; terminal anten-
nomere more elongate, 1.5X as long as
wide. Lengths of antennomeres (mm):
25.5, 21.3, 8.4, 21.3, 23.4, 14.9, 14.9, 19,
25.5, 31.9. No anterior whorls of setae
visible on any of the segments.
Thorax: Pronotum strongly convex and
transverse, much wider than long; PL =
0.12 mm, PW = 0.27 mm. Lateral margins
slightly arcuate, widest near middle; pro-
notum nearly as wide as the elytra. Ante-
rior margin nearly straight (but appearing
concave due to distortion), anterior angles
narrowly rounded, indistinct; posterior
margin nearly straight (but appearing
convex due to distortion), posterior angles
obtuse to subrectangular. Pronotum pos-
teriorly bearing 4 faint punctiform struc-
tures, possibly foveae (dif?cult to discern
as they lie on top of anterolateral notches
of mesosterna). Mesonotum with scutel-
lum large, acutely triangular posteriorly.
Metanotum with dorsomedial portion of
metascutum, scutellar groove and alary
ridges visible through the elytra, extend-
ing to a point just beyond 1/3 length of
elytra. Elytra elongate (EL = 0.41 mm,
EW = 0.18 mm) and complete, widest just
anterior to midlength, narrowing api-
cally, exposing part of tergite VI and py-
gidium (likely an artifact of compression).
Fig. 2. Ptenidium kishenehnicum Shockley and
Greenwalt, new species. Labeled structures: bsw =
basal strut of hind wing; cly = clypeus; e = eye;
el = elytron; fov = fovea; N1 = pronotum; scl =
scutellum; sclg = scutellar groove; st2 = meso-
sternum; st3 = metasternum; t = tergite; v = ventrite.
Scale bar = 0.1 mm.
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON176
Metathoracic wings visible under the
elytra, membrane narrow, basal stalk with
a single strut, trichia faint but visible
posteromedially.
Legs: Legs entirely missing or buried
in the next layer down from the re-
mainder of the body, making examina-
tion impossible.
Abdomen: Abdomen strongly com-
pressed, appearing wider (due to ?atten-
ing of the abdominal pleura) and longer
(due to stretching of the intersegmental
membranes); AL = 0.25 mm, AW =
0.30 mm. Tergites and ventrites visible
through elytra, 7 visible tergites, 6 visible
ventrites (posteriormost ventrites dif?cult
to discern). Pygidium distinct, posterior
margin smooth, acute apically, apex bear-
ing a small tuft of setae medially, no
serrations or teeth apparent. Genitalic
structures not preserved.
Material examined.?Holotype (Sex un-
known), labeled ?Ptenidium kishenehnicum
Shockley and Greenwalt. Holotype USNM
# 545816?. Deposited in NMNH. A
second specimen from an adjacent lo-
cality, Constenius Park, collected in 2012
was also examined, labeled ?Ptenidium
kishenehnicum Shockley and Greenwalt.
USNM # 553512?. Deposited in NMNH.
Etymology.?The specific epithet is a
Latinized adjective based on the geo-
logical formation where the fossil was
discovered.
Comments.?The Kishenehn ptiliid
specimen appears slightly distorted, most
likely due to dorsoventral compression
immediately postmortem or during fossil-
ization. Without a doubt the elytra and the
abdomen have been distorted from their
antemortem position by this compression,
thus making the abdomen much wider
than it would have appeared naturally.
Similarly, the pronotum appears slightly
rotated with the anterior margin appear-
ing higher than the posterior margin,
making the anterior margin artificially
appear convex rather than straight, as it
would have been in life. Although dor-
soventral compression introduced some
artifacts into the fossil, it also made
observation of more ventral structures
possible as the entire specimen was
compressed into the same focal plane.
For example, the right antenna which
bends medially at the 4th antennomere is
obscured by the head and pronotum but
is still visible due to this phenomenon.
Similarly, some abdominal features, the
struts and membrane of the hind wings
and the scutellar groove, are all visible
directly through the elytra and abdominal
tergites. Unfortunately, this ?transparency?
also makes it dif?cult to discern the two
lateral pronotal foveae (already quite
faint) because they lie directly above
the anterolateral notches of the meso-
sternum, which are heavily sclerotized
and plainly visible in the specimen. One
of the most conspicuous diagnostic fea-
tures of the family is the whorls of
setae present on the antennae. However,
poor preservation of setae and surface
sculpturing is a known artifact of com-
pression fossils so their absence in this
specimen is not particularly surprising.
Likewise, soft genitalic structures are
often not preserved and are absent in
this fossil as well, so in the absence of
secondary sexual characteristics it is
impossible to determine the sex of the
specimen.
The other specimen found at an ad-
jacent locality in 2012 is not as well
preserved as the holotype. Therefore,
we are reluctant to declare it a para-
type, despite it presenting a nearly
identical habitus to the holotype. The
relatively poor condition of this sec-
ondary fossil makes it impossible to
definitively place as P. kishenehnicum,
but it is not unreasonable to assume that
it is the same species, based on what
features are visible.
VOLUME 115, NUMBER 2 177
DISCUSSION
Carpenter (1992) ?rst suggested a
Tertiary origin for the family, most likely
during the late Eocene, as they were well
known from Baltic amber. Ponomarenko
(1995) also concluded that Ptiliidae orig-
inated in the late Eocene or early Oli-
gocene, later revising his estimate for
the origin of the family to the mid to late
Cretaceous (Ponomarenko 2002), an es-
timate congruous with the discovery of
ancient ptiliids in Lebanese and Myanmar
amber, dated to 125 and 95 Ma, respec-
tively (Rasnitsyn and Ross 2000, Grimaldi
et al. 2002, Poinar and Poinar 2008). The
presence of large numbers of ptiliids in 95
Ma Myanmar amber suggests that past
abundance and diversity may be compa-
rable or even greater than that found to-
day. The ptiliids of the Eocene likely lived
in much warmer and wetter environments
than those that exist in the Nearctic today,
and the known Kishenehn fossils thus far
represent a subtropical/temperate fauna
(Constenius et al. 1989).
Ptenidium kishenehnicum Shockley
and Greenwalt is a remarkably preserved
specimen that can be readily identi?ed as
belonging within the subfamily Ptiliinae,
tribe Ptiliini. Members of this tribe are
generally recognized by the following
combination of characters: 11-segmented
antennae, elytra complete or only slightly
shortened (last abdominal tergite only
exposed), eyes normal, procoxal cavities
open or coxae moderately separated by a
narrow prosternal process, and posterior
margin of the pygidium variable in form
(but generally not armed apically) (Hall
2000). Unfortunately, as with many fossil
descriptions, its placement in the genus
Ptenidium cannot be considered de?ni-
tive given that the ventral aspect of the
insect is not visible and characters such as
the relative placement of the coxae and
mesosternal processes, characters integral
for generic assignment, are unavailable.
However, the elytra slightly shortened,
pygidium hindmargin without a conspic-
uous apical tooth, possible presence of
pronotal fovea along hind margin, pro-
notum not constricted basally, hind an-
gles of pronotum not acute, and prothorax
without median longitudinal depression
suggest its appropriate assignment to
Ptenidium (Hall 2000, 2005).
Prior to the present study, only five
fossil ptiliids had been described at the
species level. The first to be described
was a compression fossil (Statz and
Horion 1937). This particular fossil, Ptilium
tertiarium, consisted of both a part and
counterpart, which allowed for exami-
nation of both the ventral and dorsal
surfaces. Assignment of this specimen to
the genus Ptilium was apparently based
on the presence of two ?tubercles? on the
posterior margin of the pygidium and
the pronotum with a median groove and
two smaller adjacent transverse grooves.
Polilov and Perkovsky (2004) dismissed
this assignment and suggested that, since
Ptilium tertiarium dates from the Early
Miocene (23.6?21.0 Ma) and could not
be distinguished from modern species, it
is probably an extant species. However,
the lifespan of an insect species is thought
to be 3 to 10 million years (Grimaldi and
Engel 2005) and an age of only 20+
million years is not a scienti?cally valid
basis for assuming that P. tertiarium is an
extant species.
Ptinella oligocoenica and Microptilium
geistautsiwere both described from Baltic
amber (Parsons 1939, Dybas 1961). The
description of P. oligocoenica did not
include a basis for the assignment to the
genus Ptinella and the assignment of
M. geistautsi appears to be based on a
comparison of drawings of the specimen
to an accompanying description of the
extant species M. pulchellum. The de-
scription of M. geistautsi consists only of
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON178
a detailed description of the antennae, the
fossil?s color and presence of dorsal setae.
The two species described by Polilov and
Perkovsky (2004) were both identi?ed
as female. Ptinella rovnoensis retained a
small spherical spermatheca, a remark-
able example of preservation given that
this fossil insect is only 910 mm long.
Ptinella rovnoensis lacks hind wings and
is thought to be a vestigial morph, a form
known to exist within the genus Ptinella
(Dybas 1978). Polilov and Perkovsky
(2004) also reported two poorly pre-
served specimens identi?ed to the genus
Ptenidium and ?ve additional specimens
of Ptilium to which they did not assign
species names as they were unable to ex-
amine the male genitalia and thus could
not distinguish them from recent species.
We would counter that inability to
distinguish new fossil ptiliids from ex-
tant species should not, in and of itself,
preclude their designation as new spe-
cies. Although there are large numbers
of fossil Ptiliidae reported from several
amber sites around the world ranging
in age from 20 Ma to 120 Ma, only six
specimens of Ptiliidae have been officially
designated as new species. Dismissal of
Ptilium tertiarium as an extant species and
the requirement by Polilov and Perkovsky
(2004) of comparing genitalia to recent
species are based on unrealistic criteria
that inhibit efforts to describe the many
ptiliid fossils that exist. We do not mean
to propose that, when feasible, such
comparisons should not be made, but
the literature is rife with descriptions of
fossil species that have never been com-
pared to extant species or are anatomically
indistinguishable from extant species.
Similarly, specimens assigned the status
of ?incertae sedis? or ?species indeter-
minate?, the only alternative to formal
designation as new species, are rarely
fully described in the scienti?c litera-
ture. Unfortunately, since so many fossil
ptiliids remain undescribed or unassigned
generic or species names, evaluating those
records becomes impossible without some
explicit method for identifying speci?c
specimens and determining if those re-
cords are distinct or duplicate.
Although P. kishenehnicum is the ?rst
fossil of its family to be described from
the New World, specimens have been
recorded from both Dominican and
Mexican amber. Thus, we hope that its
description will renew interest in de-
scribing those specimens as well, with-
out the constraints adopted by Polilov
and Perkovsky (2004). Increased input
into the comparative database of fossil
Ptiliidae is much needed and desirable
for a greater understanding of the evolu-
tion of this unique and interesting family
of miniscule beetles.
ACKNOWLEDGMENTS
We thank Karie Darrow (Dept. of
Entomology, National Museum of Nat-
ural History, Smithsonian Institution) for
taking the high resolution habitus im-
ages. We also thank the two anonymous
reviewers whose comments and sugges-
tions significantly improved the manu-
script. This is contribution number 279 of
the Evolution of Terrestrial Ecosystems
consortium at the National Museum of
Natural History in Washington, D.C.
Literature Cited
Bachofen-Echt, A. 1949. Der Bernstein und
seine Einschlu?sse. Springer-Verlag, Wien.
204 pp.
Carpenter, F. M. 1992. Treatise on Invertebrate
Paleontology. Part R, Arthropoda 4, Volume
4. Superclass Hexapoda. Geological Society
of America, Boulder, CO. 655 pp.
Constenius, K. N., M. R. Dawson, H. G. Pierce,
R. C. Walter, and M. V. H. Wilson. 1989. Re-
connaissance paleontologic study of the
Kishenehn Formation, northwestern Montana
and southeastern British Columbia. Montana
Geological Society 1989 Field Conference,
VOLUME 115, NUMBER 2 179
Montana Centennial. Geological Resources of
Montana 1: 189?203.
Constenius, K. 1996. Late Paleogene extensional
collapse of the Cordilleran foreland fold and
thrust belt. Geological Society of America
Bulletin 108(1): 20?39. doi:10.1130/0016-
7606(1996)108<0020:LPECOT>2.3.CO;2
Dybas, H. S. 1961. A new fossil feather-wing
beetle from Baltic amber (Coleoptera:
Ptiliidae). Fieldiana. Zoology (Jena, Germany)
44(1): 1?9.
Dybas, H. S. 1978. Polymorphism in featherw-
ing beetles, with a revision of the genus
Ptinelloides (Coleoptera: Ptiliidae). Annals
of the Entomological Society of America 71:
695?714.
Erichson, W. F. 1845. Vol. 3. Naturgeschichte der
Insecten Deutschlands. Erste Abtheilung, Cole-
optera. Verlag der Nicolaischen Buchhandlung,
Berlin. 320 pp.
Grebennikov, V. V. 2008. How small you can go:
Factors limiting body miniaturization in winged
insects with a review of the pantropical genus
Discheramocephalus and description of six
new species of the smallest beetles (Pterygota:
Coleoptera: Ptiliidae). European Journal of
Entomology 105: 313?328.
Grebennikov, V. V. 2009. Discheramocephalini,
a new pantropical tribe of featherwing bee-
tles (Coleoptera: Ptiliidae): description of
new taxa and phylogenetic analysis. System-
atic Entomology 34: 113?136. doi:10.1111/
j.1365-3113.2008.00444.x
Greenwalt, D. E., F. Marsh, and C. C. Labandeira.
2011. Preliminary Characterization of the En-
tomofauna of the Middle Eocene Kishenehn
Basin. Proceedings of the GSA Joint Rocky
Mountain/Cordilleran Sections meeting 43(4):
13.
Grimaldi, D. A., M. S. Engel, and P. C. Nascimbene.
2002. Fossiliferous Cretaceous amber from
Myanmar (Burma): Its rediscovery, biotic diver-
sity, and paleontological signi?cance. American
Museum Novitates 3361: 1?72. doi:10.1206/
0003-0082(2002)361<0001:FCAFMB>2.0.
CO;2
Grimaldi, D. and M. S. Engel. 2005. Evolution of
the Insects. Cambridge University Press, New
York. 755 pp.
Hall, W. E. 2000. Ptiliidae Erichson, 1845, pp.
233?246. In Arnett, Jr., R. H., and M. C.
Thomas, eds. American Beetles. Vol. 1. Arch-
ostemata, Myxophaga, Adephaga, Polyphaga:
Staphyliniformia. CRC Press, Boca Raton, FL.
443 pp.
Hall, W. E. 2005. Ptiliidae, pp. 251?261. In
Beutel, R. G. and R. A. B. Leschen, eds.
Handbook of Zoology, Volume 4. Arthropoda:
Insects: Part 38. Coleoptera, Beetles. Volume
1: Morphology and Systematics. De Gruyter,
Berlin/New York. 567 pp.
Handlirsch, A. 1925. Pala?ontologie, pp. 117?306.
In C. W. M. Schro?der, ed. Handbuch der
Entomologie, Vol. 3. Gustav Fischer, Jena,
Germany. 1201 pp.
Helm, O. 1896. Beitra?ge zur Kenntniss der Insecten
des Bernsteins. Schriften der Naturforschenden
Gesellschaft in Danzig N.F. 8: 220?231.
Horridge, G. A. 1956. The ?ight of very small
insects. Nature 178: 1334?1335. doi:10.1038/
1781334a0
Huber, J. T. and D. Greenwalt. 2011. Compres-
sion fossil Mymaridae (Hymenoptera) from
Kishenehn oil shales, with description of two
new genera and review of Tertiary amber
genera. ZooKeys 130: 473?494. doi:10.3897/
zookeys.130.1717
Klebs, R. 1910. U?ber Bernsteineinschlu?sse im
allgemeinen und die Coleopteren meiner
Bernsteinsammlung. Schriften der Physikalisch-
O?konomischen Gesellschaft zu Ko?nigsberg
51(3): 217?242.
Kulicka, R. and S. A. Slipinski. 1996. A review of
the Coleoptera inclusions in the Baltic amber.
Prace Muzeum Ziemi 44: 5?11.
Larsson, S. G. 1978. Vol. 1. Baltic Amber ? a
palaeobiological study. Scandinavian Science
Press Ltd., Klampenborg, Denmark. 192 pp.
Matthews, J. V., Jr. 1977. Tertiary Coleoptera
fossils from the North American Arctic. Co-
leopterists Bulletin 31(4): 297?308.
Matthews, J. V., Jr. and A. Telka. 1997. Insect
fossils from the Yukon, pp. 911?962. In H. V.
Danks and J. A. Downes, eds. Insects of the
Yukon. Biological Survey of Canada. Ter-
restrial Arthropods, Ottawa. 1034 pp.
Parsons, C. T. 1939. A ptiliid beetle from Baltic
amber in theMuseum of Comparative Zoology.
Psyche 46: 62?64. doi:10.1155/1939/86451
Poinar, G. O., Jr. 1992. Life in Amber. Stanford
University Press, Stanford, CA. 350 pp.
Poinar, G. O., Jr. and R. Poinar. 1999. The Amber
Forest: A Reconstruction of a Vanished World.
Princeton University Press, Princeton. 239 pp.
Poinar, G. O., Jr. and R. Poinar. 2008. What
Bugged the Dinosaurs? Insects, Disease, and
Death in the Cretaceous. Princeton Univer-
sity Press, Princeton. 264 pp.
Polilov, A. A. 2005. Anatomy of the feather-
winged beetles Acrotrichis montandoni and
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON180
Ptiliummyrmecophilum (Coleoptera, Ptiliidae).
Entomological Review 85: 467?475.
Polilov, A. A. and E. E. Perkovsky. 2004. New
species of late Eocene feather-winged beetles
(Coleoptera, Ptiliidae) from the Rovno and
Baltic amber. Paleontological Journal 38(6):
664?668.
Ponomarenko, A. G. 1995. The geological history
of beetles, pp. 155?171. In J. Pakaluk and
S. A. Slipinski, eds. Biology, Phylogeny, and
Classi?cation of Coleoptera: Papers Celebrating
the 80th Birthday of Roy A. Crowson. Muzeum
i Instytut Zoologii PAN, Warszawa. 1092 pp.
Ponomarenko, A. G. 2002. Superorder Scar-
abaeidea Laicharting, 1781. Order Coleoptera
Linne, 1758. The beetles, pp. 164?176. In A. P.
Rasnitsyn and D. L. J. Quicke, eds. History of
insects. Kluwer, Dordrecht. 524 pp.
Rasnitsyn, A. P. and A. J. Ross. 2000. A pre-
liminary list of arthropod families present in
the Burmes amber collection at The Natural
History Museum, London. Bulletin of the
Natural History Museum. London (Geology)
56: 21?24.
Statz, G. and A. Horion. 1937. Ein fossiler
Ptiliidenfund aus den mitteloligocanen Abla-
gerungen von Rott am Siebengebirge. Ento-
mologische Blatter 38: 8?10.
Spahr, U. 1981. Systematischer Katalog der Bern-
stein- und Kopal-Ka?fer (Coleoptera). Stuttgarter
Beitrage zur Naturkunde. Serie B, Geologie und
Palaontologie 80: 1?107.
Wu, R. J. C. 1996. Secrets of a Lost World: Do-
minican Amber and its Inclusions. R. J. C.
Wu, Santo Domingo, Dominican Republic.
222 pp.
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