THE CRETACEOUS AND PALEOCENE PLEUROTOMARIID
(GASTROPODA: VETIGASTROPODA) FAUNA OF SEYMOUR
ISLAND, ANTARCTICA
M. G. HARASEWYCH,1 ANTON OLEINIK,2 AND WILLIAM ZINSMEISTER3
1Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, PO Box 37012,
Washington, DC 20013-7012, ,HARASEWYCH@si.edu.; 2Department of Geosciences, Florida Atlantic University, 777 Glades Road,
Boca Raton, FL, 33431-0991, ,aoleinik@fau.edu.; and 3Department of Earth and Atmospheric Sciences, Purdue University,
1397 Civil Engineering Building, West Lafayette, IN 47907-1397, ,wjzins@purdue.edu.
THE CRETACEOUS AND PALEOCENE PLEUROTOMARIID
(GASTROPODA: VETIGASTROPODA) FAUNA OF SEYMOUR
ISLAND, ANTARCTICA
M. G. HARASEWYCH,1 ANTON OLEINIK,2 AND WILLIAM ZINSMEISTER3
1Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, PO Box 37012,
Washington, DC 20013-7012, ,HARASEWYCH@si.edu.; 2Department of Geosciences, Florida Atlantic University, 777 Glades Road,
Boca Raton, FL, 33431-0991, ,aoleinik@fau.edu.; and 3Department of Earth and Atmospheric Sciences, Purdue University,
1397 Civil Engineering Building, West Lafayette, IN 47907-1397, ,wjzins@purdue.edu.
ABSTRACT?Leptomaria antipodensis and Leptomaria hickmanae are described from the Upper Cretaceous
[Maastrichtian] Lopez de Bertodano Formation, Seymour Island, and represent the first Mesozoic records of the
family Pleurotomariidae from Antarctica. Leptomaria stillwelli, L. seymourensis, Conotomaria sobralensis and C.
bayeri, from the Paleocene [Danian], Sobral Formation, Seymour Island, are described as new. Leptomaria
larseniana (Wilckens, 1911) new combination, also from the Sobral Formation, is redescribed based on better-
preserved material. The limited diversity of the pleurotomariid fauna of Seymour Island is more similar to that of
the Late Cretaceous faunas of Australia and New Zealand in terms of the number of genera and species, than to the
older, more diverse faunas of South America, southern India, or northwestern Madagascar, supporting the status of
the Weddelian Province as a distinct biogeographic unit. The increase in the species richness of this fauna during the
Danian may be due to the final fragmentation of Gondwana during this period.
INTRODUCTION
THE THICK sequence of loosely consolidated fossiliferousrocks on Seymour Island represents the most nearly
complete and well-exposed shallow-marine section of Upper
Cretaceous to lower Tertiary rocks known in the Southern
Hemisphere (Zinsmeister, 1982a). Cretaceous and Tertiary
marine mollusks from Seymour Island were first described a
century ago by Sharman and Newton (1894) and Wilckens
(1910, 1911). However, extensive field work on Seymour
Island from 1970 through the 1990s revealed much greater
molluscan species diversity than had previously been encoun-
tered. This was particularly true for the Late Cretaceous and
early Paleocene molluscan faunas, which are neither as
common nor as well preserved as those of the Eocene (Stillwell
et al., 2004). Only one species of the family Pleurotomariidae,
Leptomaria larseniana (Wilckens, 1911), had previously been
described from the Paleocene of the Seymour Island. The 1994
to 1995 field season on Seymour Island yielded six additional
species of Pleurotomariidae belonging to two genera?
Leptomaria E. Eudes-Deslongchamps, 1864, and Conotomaria
Cox, 1959. These species from the Lopez de Bertodano and
Sobral formations range in age from Late Maastrichtian to
Early Danian. Three Early Paleocene species of Conotomaria
were figured by Stillwell et al. (2004) but were not formally
described. This review of the pleurotomariid assemblage
constitutes the first detailed record of Late Cretaceous to
Early Paleocene pleurotomariid gastropods from the continent
of Antarctica. This newly described pleurotomariid fauna
sheds light on the evolution and biogeographic history of the
family Pleurotomariidae in the Southern Hemisphere.
GEOLOGIC SETTING
The upper Cretaceous and lower Paleocene sedimentary
sequence of Seymour Island was described by Anderson
(1906), Rinaldi et al. (1978), Zinsmeister (1982a), Macellari
and Huber (1982), Macellari and Zinsmeister (1983), Huber
(1984), Macellari (1984, 1986, 1988), Sadler (1988), and
Stilwell and Zinsmeister (1992) and consists of approximately
1600 m of gently eastward-dipping fossiliferous marine
clastics. Two major stratigraphic units are recognized for the
upper Cretaceous and lower Paleocene part of the sequence,
the Lopez de Bertodano and Sobral formations. These units
comprise the upper part of the Marambio Group (Rinaldi,
1982; Macellari, 1984).
The Lopez de Bertodano Formation (Figs. 1, 2) consists of
approximately 1,200 m of tan to medium-gray, concretion-
bearing sandstone with occasional horizons of silty sandstone
and siltstone (Fig. 2). Some horizons are enriched with
limonite, which gives them a reddish-brown color. Hard
carbonate concretions are scattered throughout the section.
Concretions are spherical to irregularly rounded, range in size
from 2 cm up to 1 m in diameter, and commonly contain
mollusks preserved in the center. Near the top of the Lopez de
Bertodano Formation, concretions seem to become less
abundant, and the sandstone grades into light tan siltstone.
Finer-grained, medium-gray, sandy siltstones without concre-
tions occur at several horizons throughout the formations.
Beds with a large number of concretions tend to form higher
and steeper hills as compared with layers free of concretions
(Zinsmeister, 1982a). The Lopez de Bertodano Formation is
characterized by a large number of well-preserved ammonites,
most of which occur in concretions (Zinsmeister, 1982a;
Macellari, 1986). Bored and abraded wood debris ranging in
size up to 1 m in diameter, bivalves, and gastropods are
commonly encountered throughout the sequence. The highly
bioturbated nature of the sediments and the absence of
primary sedimentary structures indicate that deposition was,
in all likelihood, mid-shelf below effective wave-base (Macel-
lari and Zinsmeister, 1983; Macellari, 1988). The age of the
Lopez de Bertodano Formation ranges from Maastrichtian
through Early Paleocene. An Early Paleocene (Danian stage)
age determination of the uppermost unit of the Lopez de
Bertodano Formation was based on dinoflagellates (Palmarc-
zuk et al., 1984) and siliceous microfossils (Harwood, 1988), as
well as planktic and benthic foraminifers (Huber, 1988). The
Lopez de Bertodano Formation is overlain by the slightly
sandier Lower Paleocene Sobral Formation. Although there is
a disconformity between the Lopez de Bertodano and Sobral
J. Paleont., 83(5), 2009, pp. 750?766
Copyright ? 2009, The Paleontological Society
0022-3360/09/0083-0750$03.00
750
FIGURE 1?Localities on Seymour Island from which Cretaceous and Paleocene pleurotomariids have been collected.
FIGURE 2?Stratigraphic distribution of Pleurotomariidae in the Upper Cretaceous and Lower Paleogene sediments of the Seymour Island. 1 5
medium to fine-grained sandstone, 2 5 mudstone, 3 5 siltstone, 4 5 glauconite.
FIGURES 3?4?Drawings of 3, umbilicate [phaneromphalous] and 4, non-umbilicate [anomphalous] pleurotomariids, illustrating descriptive terms
used in the text. b, base; p, periphery; pb, peripheral bulge; ra, ramp angle; s, suture; sa, spire angle; sl, slit; st, spiral threads, sz, selenizone; u, umbilicus.
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 751
formations, faunal similarities between the two units indicate
that little time is missing (Elliot and Trautman, 1982; Rinaldi
et al., 1978; Macellari and Zinsmeister, 1983; Macellari, 1988).
The Sobral Formation (Figs. 1, 2) consists of approximately
255 m (Macellari, 1988) of silty to medium-grained, well-
bedded, dark brown to greenish-grey concretionary sandstone.
The lower part of the Sobral Formation consists of 40?90 m of
loosely consolidated greenish-grey glauconitic sandstone. The
upper 120?170 m of Sobral sandstones is essentially the same
in composition but better cemented and more resistant to
erosion than the lower part. The combination of numerous
concretions in the lower part of the formation and resistant
beds overlying the concretionary horizons results in the
development of higher and steeper hills as compared to the
lower gently rolling topography of the Lopez de Bertodano
Formation. Cross-bedding on a scale of 1?3 m becomes well
developed and fossil remains become more poorly preserved
and less abundant in the uppermost 100 m of the Sobral
Formation (Zinsmeister and Macellari, 1988; Stillwell and
Zinsmeister, 1992). The upper half of the Lopez de Bertodano
Formation and lower part of the Sobral Formation are
characterized by diverse and well-preserved marine mega-
fossils, dominated by mollusks. Corals, brachiopods, annelid
tubes, scaphopods, decapods, echinoderms, marine reptiles
and fishes are locally abundant. An early Paleocene (Danian
stage) age of the Sobral Formation has been established based
on the dinoflagellates (Hall, 1977), planktonic and benthic
foraminifers (Huber, 1988; Palmarczuk et al., 1984), and
spores and pollen (Askin, 1988), as well as on radiometric
dating of glauconite (Macellari, 1984). Specimens used and
figured in this paper were collected during the 1994?1995 field
seasons on Seymour Island.
Figured types are housed in the United States National
Museum of Natural History, Smithsonian Institution, Wash-
ington, D.C. (USNM). Additional material is housed in the
invertebrate fossil collection of the Department of Earth and
Atmospheric Sciences, Purdue University (EASPU).
SYSTEMATIC PALEONTOLOGY
Class GASTROPODA Cuvier, 1797
Subclass ORTHOGASTROPODA Ponder and Lindberg, 1997
Superorder VETIGASTROPODA Salvini-Plawen, 1989
Superfamily PLEUROTOMARIOIDEA Swainson, 1840
Family PLEUROTOMARIIDAE Swainson, 1840
Genus LEPTOMARIA E. Eudes-Deslongchamps, 1864
Type species.?Pleurotomaria amoena J. A. Eudes-Deslong-
champs, 1849 (By original designation). Bajocian (Middle
Jurassic) of France.
Diagnosis.???Conical or cyrtoconoid, anomphalous to
broadly phaneromphalous; whorls weakly to strongly convex,
not angular, last one rounded at periphery of convex base;
selenizone at mid-whorl; ornament spiral threads that may be
cancellated by collabral threads. Middle Jurassic (Bajocian) to
Upper Cretaceous (Danian). Cosmopolitan.?? (Knight et al.,
1960, p. I219)
Range.?Middle Jurassic (Bajocian) to Paleocene (Thane-
tian; range extended by Pacaud, 2004:fig. 20). Cosmopolitan.
Remarks.?Harasewych and Kiel (2007, p. 77?78) provided
an updated synopsis of the supraspecific classification within
the family Pleurotomariidae and summarized the currently
recognized geological ranges of the genera and subgenera
(Harasewych and Kiel (2007, fig. 3, Appendix 1) as well as the
characters used to distinguish them (Harasewych and Kiel
(2007, table 1). Pacaud (2004, fig. 20) reported Pleurotomaria
Defrance, 1826 from multiple Danian (Paleocene) records
throughout Europe and extended the ranges of both
Conotomaria and Leptomaria into the Thanetian (Paleocene).
These three genera are the only genera that are currently
recognized as having survived from the Mesozoic into the
Cenozoic.
Whereas the generally applied diagnosis of Leptomaria
accommodates a broad range of morphologies, the type
species, Leptomaria amoena, is large, with strongly convex
whorls, a well-rounded periphery along the last whorl, a
selenizone situated at mid-whorl, and lacking an umbilicus.
LEPTOMARIA LARSENIANA (Wilckens, 1910) new combination
Figures 5?6, Table 1
Pleurotomaria larseniana WILCKENS, 1910, p. 73, pl. 3, fig. 24.
Original description (translated).???Only the internal
mold of the shell is present. Apex and aperture are
missing. Not quite three whorls are preserved. The shape
of the shell is broadly conical, the whorls are laterally
flattened and roundly edged below. The selenizone seems
to have lain quite close above this edge. The base of the
last preserved whorl shows weak curvature. Toward the
final whorl, the shell seems to have had strong growth
striae.
I name this species after the deserving leader of the ship
of the Swedish South Pole expedition, Captain Larsen,
who brought the first fossils from the Antarctic.
Dimensions:
Height (incomplete!). . . . . . . . . . . . . . . . . . . 98 mm.
Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 mm.
Discovery site: Seymour Island, Locality 9: 1 specimen
(internal mold).
Similar species: Comparison with other species is made very
difficult by the poor preservation of the single specimen,
which makes the description of a new species appear
somewhat daring. A Pleurotomaria of similarly enormous
dimensions, but with a flatter shell shape is Pl. tardensis
Stanton from the Belgrano layers. The form of the whorls is
not very different from that of Pl. larseni. Stanton noted that
no other Cretaceous species is known to him that could be
considered for comparison. There are no similar forms
described from the Cretaceous of India, and the Upper
Cretaceous and Tertiary of Argentina have not yet produced
any Pleurotomaria.?? (Wilckens, 1910, p. 73).
Redescription.?Shell large for genus (maximum diameter
100.4 mm, minimum diameter 85.1 mm, height 108.8 mm),
with a tall, broadly conical spire consisting of eight preserved
teleoconch whorls. Base weakly but evenly convex, lacking an
FIGURE 5?Leptomaria larseniana (Wilckens, 1911). Reproduction of
the original illustration (Wilckens, 1911, pl. 3, fig. 24, as Pleurotomaria
larseniana). Scale bar 5 2 cm.
752 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
umbilicus (Fig. 6.4). Spire angle ,68u. Spire evenly conical in
profile. Suture (Fig. 6.5) weakly adpressed, joining previous
whorl at or above a weak peripheral bulge (Fig. 6.1).
Protoconch and approximately first two teleoconch whorls
missing. Subsequent early whorls very weakly gradate, slightly
convex, without distinct ramp angle. Spiral sculpture domi-
nant, of six to seven low, narrow cords as broad as intervening
spaces between suture and selenizone, and 12?15 between
selenizone and peripheral bulge. Base with similar spiral cords,
estimated to be 19?22 on final whorl. Selenizone (Fig. 6.5)
broad (selenizone width/suture to suture distance 5 0.24),
weakly convex, situated at mid-whorl. Surface without spiral
cords, sculpture limited to strong lunulae. Axial sculpture
limited to fine growth striae that become conspicuously
FIGURE 6?Leptomaria larseniana (Wilckens, 1911). 1, apertural; 2, dorsal; 3, apical, and 4, basal views of specimen from locality 9, Seymour Island,
USNM 467213. 5, Details of sculpture on the dorsal surface of whorls five through seven. Scale bars 5 2.0 cm, pb, peripheral bulge; s, suture;
sz, selenizone.
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 753
coarser and more irregular on last quarter whorl. Aperture
broadly elongate, long axis deflected from the coiling axis by
,104u. Outer lip damaged, slit broad (6.2 mm), extending for
less than J whorl. Inner lip thickest along columellar region,
where it forms a narrow parietal callus.
Type locality.?Seymour Island, Antarctic Peninsula
(Fig. 1, Locality 9, 64u16952.580S, 56u42950.640W).
Material examined.?USNM 467213, Paleocene, Danian,
Sobral Formation.
Stratigraphic occurrence.?1,167 m (Fig. 2).
Remarks.?The taxon Pleurotomaria larseniana was based
on a unique, partial internal mold comprising nearly three
whorls, but lacking apex, aperture, or any remnants of shell
material (Fig. 5). A redescription of this species, based on
a more nearly complete specimen (Fig. 6.1?6.5) from the
type locality is provided. This species is transferred to the
genus Leptomaria on the basis of its high spire, rounded
whorl profile, position of selenizone at mid-whorl, absence
of shoulder, lack of nodes along periphery or significant
axial sculpture and, like the type species, lack of an
umbilicus.
Wilckens (1910, p. 73) compared his new species with
Pleurotomaria tardensis Stanton, 1901 from the Belgrano beds
[Barremian, Lower Cretaceous] of Argentina, noting that P.
larseniana was of similar size but that P. tardensis had a much
flatter shape. Subsequently, Weaver (1931) reported on four
species of pleurotomariids from the Jurassic and early
Cretaceous of west-central Argentina. Of the Argentinian
pleurotomariids known to date, the Jurassic [Callovian]
Leptomaria leufuensis (Weaver, 1931), new combination, most
closely resembles L. larseniana in shape. However, it is much
smaller (55 mm diameter), slightly lower spired (spire angle
estimated at 70u), with a narrow selenizone, and a moderately
developed umbilicus.
Leptomaria larseniana does not appear to have close
relatives in the Maastrichtian of western Australia (Darragh
and Kendrick, 1994). Wilckens (1922, p. 3) compared his
Pleurotomaria maoriensis [Amuri Group, Late Cretaceous and
Paleocene, of New Zealand (Roberts, 1992, fig. 2)] with L.
larseniana, but the two can be easily distinguished, as P.
maoriensis has a shoulder. Among the Cretaceous species from
India, L. indica Stoliczka, 1868 [Ootatoor Group, Cenoma-
nian and Arrialoor Group, Maastrichtian] is comparable is
size, but is broadly umbilicate, whereas P. glabella Stoliczka,
1868 [Ootatoor Group] is similarly high spired, but smaller,
with less inflated whorls, much broader selenizone and more
sharply angled periphery.
Leptomaria larseniana resembles L. gyroplata (Eudes-
Deslongchamps, 1849) (see Gru?ndel, 2003, pl. 1, figs. 12?14)
from the Bajocian (Middle Jurassic) of southern Germany in
terms of size, proportions, absence of umbilicus, shape of
whorls, and position and of selenizone.
LEPTOMARIA STILWELLI new species
Figure 7, Table 1
Diagnosis.?Shell large, cyrtoconoid, spire angle ,96u,
weakly gradate, anomphalous; whorls convex; aperture
broadly oval; selenizone narrow, just below mid-whorl;
peripheral band weak; spiral sculpture dominant, intersected
by weak growth striae.
Description.?Shell large (holotype, maximum diameter
95.1 mm, minimum diameter 78.0 mm, height 68.4 mm), with
a moderately high, broadly trochiform spire, consisting of
three and three quarter preserved teleoconch whorls. Base
somewhat inflated, broadly convex, lacking an umbilicusTA
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754 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
(Figure 7.4). Spire angle ,96u. Spire conical, weakly gradate
in profile. Suture (Fig. 7.5) abutting, joining previous whorl
long the top of a weak peripheral bulge (Fig. 7.1). Protoconch
and first several teleoconch whorls missing. Subsequent whorls
weakly gradate, smoothly convex, with a distinct ramp angle.
Spiral sculpture dominant, with an estimated 13?15 broad,
closely spaced cords between suture and selenizone, and three
to five between the selenizone and periphery. Sculpture along
base not well preserved, region near columella smooth
(Fig. 7.4). Selenizone (Fig. 7.5) narrow (selenizone width/
suture to suture distance 5 0.16), weakly convex, situated
slightly below mid-whorl. Lunulae concave, surface sculpture
unknown. Axial sculpture limited to fine growth striae on
early whorls, with weak, low rugae (about 40) developing on
final whorl. Aperture broadly ovate, long axis deflected from
the coiling axis by ,100u. Outer lip damaged, slit narrow,
4.1 mm, extending for less than one quarter whorl. Shell
thickest along inner lip and base near columellar region
(2.2 mm), adjacent to a broad, nacreous parietal callus
(Fig. 7.4).
Etymology.?This species is named for Dr. Jeffery D.
Stilwell, School of Geosciences, Monash University, Mel-
bourne, Australia, for his contribution to the study of
Cretaceous and early Tertiary faunas of the Southern
Hemisphere.
Types.?Holotype, USNM 467214, Paleocene, Danian,
Sobral Formation, Seymour Island, Antarctic Peninsula
(Fig. 1, Locality 9; 64u16952.580S, 56u42950.640W).
Stratigraphic occurrence.?1,167 m (Fig. 2).
Remarks.?Leptomaria stilwelli co-occurs with L. larseniana
but can be readily distinguished from that species by its lower,
more gradate spire, more inflated base, and narrower
FIGURE 7?Leptomaria stillwelli new species. 1, apertural; 2, dorsal; 3, apical, and 4, basal views of the holotype, USNM 467214. Locality 9, Seymour
Island. 5, Details of sculpture on dorsal surface. Scale bars 5 2.0 cm, p, periphery; pb, peripheral bulge; pc, parietal callus; s, suture; sz, selenizone.
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 755
selenizone, as well as by the presence of axial rugae on the final
whorl.
It does not appear to be similar to fossils reported from the
Cretaceous of New Zealand or Australia, but it resembles
Leptomaria leufuensis [Callovian, Argentina], from which it may
be separated on the basis of its larger size, more inflated whorls,
and absence of an umbilicus, and from L. daityai Das, Bardhan
and Kase, 2005 [Callovian?Oxfordian, NW India], which is
similar in size and sculpture, but is umbilicate and has strong
spiral sculpture along the base, which is lacking in L. stillwelli.
FIGURE 8?Leptomaria seymourensis new species. 1, apertural; 2, dorsal; 3, apical, and 4, basal views of the holotype, USNM 467215. Station 746,
Seymour Island. 5, Details of sculpture on dorsal surface of holotype; 6, apertural, and 7, basal views of paratype 1. USNM 467216. Locality 746,
Seymour Island. Scale bars 5 2.0 cm, p, periphery; pb, peripheral bulge; pc, parietal callus; s, suture; sz, selenizone.
756 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
LEPTOMARIA SEYMOURENSIS new species
Figures 8?9, Table 1
Conotomaria species C; STILWELL, ZINSMEISTER AND OLEI-
NIK, 2004, p. 26, pl. 4, fig. 5, 6.
Diagnosis.?Shell large, cyrtoconoid, weakly gradate, spire
angle ,84u, anomphalous; whorls weakly convex; aperture
broadly rhomboidal; selenizone narrow, just below mid-
whorl; peripheral band weak; spiral sculpture dominant,
reticulate sculpture present on early whorls and along shell
base.
Description.?Shell large for genus (holotype, maximum
diameter 94.4 mm, minimum diameter 75.8 mm, height
81.4 mm; paratype 2, maximum diameter 118.4 mm, mini-
mum diameter 102.2 mm, height 87.5 mm), with a broadly
conical spire consisting of eight preserved teleoconch whorls.
Base weakly sigmoidal, slightly concave near periphery,
slightly convex near axis, lacking an umbilicus (Fig. 8.4).
Spire angle ,84u. Spire weakly gradate in profile. Suture
(Fig. 8.5) abutting previous whorl along top of a peripheral
bulge (Figs. 8.2, 8.4) that becomes more pronounced in later
whorls. Protoconch and first few teleoconch whorls absent in
holotype and paratypes. Subsequent teleoconch whorls
become progressively more convex between suture and
selenizone without producing an angled shoulder. Region
between selenizone and periphery straight to slightly convex.
Spiral sculpture dominant, with 13?15 low, narrow cords
between the suture and selenizone, 9?11 between the
selenizone and periphery. Cords more prominent and closely
spaced near the suture and periphery, finer and more widely
spaced near the selenizone. Base with 31?33 evenly spaced
spiral cords that become slightly more pronounced adaxially.
Selenizone (Fig. 8.5) narrow (selenizone width/suture to
suture distance 5 0.13), flat to weakly convex, situated
slightly below mid-whorl. Surface with strong lunulae and
zero to one spiral cords in early whorls, thereafter with
weaker, less concave lunulae and without spiral sculpture.
Axial sculpture of fine growth striae that may produce
reticulate sculpture on early whorls and along shell base.
Aperture broadly rhomboidal, long axis deflected from the
coiling axis by 112?114u. Outer lip damaged, slit narrow
,3.5 mm, extending for less than one third whorl. Inner lip
thickest along base and columellar region, where it forms a
narrow, nacreous parietal callus.
Etymology.?Named after its type locality, Seymour Island,
Antarctica.
Types.?Holotype, USNM 467215, Paratype 1, USNM
467216, Paratype 2, USNM 467217, all Paleocene, Danian,
Lopez de Bertodano Formation, Seymour Island, Antarctic
Peninsula (Fig. 1, Locality 746; 64u19902.40S, 56u48942.40W).
Stratigraphic occurrence.?1,134 m (Fig. 2).
Remarks.?Leptomaria seymourensis appears lower in the
stratigraphic column than L. larseniana and L. stillwelli. It is
similar to L. stillwelli in spire height but can be readily
distinguished from this species on the basis of its more gradate
spire, angled periphery, more pronounced peripheral band,
and flatter base. Leptomaria seymourensis more closely
resembles L. larseniana in whorl profile but has a narrower
selenizone and stronger spiral cords, especially along the base.
Unlike other species from Seymour Island, L. seymourensis
has finely reticulate sculpture on the early whorls. Leptomaria
seymourensis also resembles L. asurai Das, Bardhan and Kase,
2005 [Callovian?Oxfordian, NW India] but has a lower, more
stepped spire, less inflated whorls, and a more quadrate
aperture.
LEPTOMARIA HICKMANAE, new species
Figure 10, Table 1
Diagnosis.?Shell large, cyrtoconoid, spire angle ,70u,
anomphalous; whorls strongly convex; aperture broadly
ovate; selenizone broad, just below mid-whorl; peripheral
band weak; spiral sculpture dominant.
FIGURE 9?Leptomaria seymourensis new species. 1, apertural; 2, apical,
and 3, basal views of paratype 2, USNM 467217. Locality 746, Seymour
Island. Scale bar 5 2.0 cm.
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 757
Description.?Shell large for genus (maximum diameter
90.2 mm, minimum diameter 79.9 mm, height 81.0 mm), with
a tall, broadly trochiform spire, consisting of three and a half
preserved teleoconch whorls. Base inflated, broadly convex,
lacking an umbilicus (Fig. 10.4). Spire angle ,70u. Spire
evenly conical in profile. Suture adpressed, joining previous
whorl at or above a weak peripheral bulge (Figs. 10.1, 10.2).
Protoconch and approximately first four teleoconch whorls
missing. Subsequent whorls very weakly gradate, smoothly
convex, without distinct ramp angle. Spiral sculpture domi-
nant, with an estimated 15?18 low, narrow cords slightly
broader than intervening spaces between suture and seleni-
zone, and 9?11 between selenizone and periphery. Base with
similar but weaker spiral cords, estimated to be 36 on final
whorl. Selenizone moderately wide (Fig. 10.2; selenizone
width/suture to suture distance 5 0.17), weakly convex,
situated slightly below mid-whorl. Lunulae concave, surface
sculpture unknown. Axial sculpture limited to fine growth
striae. Aperture broadly ovate, long axis deflected from the
coiling axis by ,102u. Outer lip damaged, slit moderately wide
5.5 mm, extending for less than one third whorl. Inner lip
thickest along columellar region, where it forms a narrow,
nacreous parietal callus (Fig. 10.4).
Etymology.?This species is named for Dr. Carole S.
Hickman of the University of California at Berkeley, in
recognition of her contributions to the study of living and
fossil Pleurotomariidae.
Types.?Holotype, USNM 467218, Upper Cretaceous,
Maastrichtian, Lopez de Bertodano Formation, Sey-
mour Island, Antarctic Peninsula (Fig. 1, Locality K 423;
64u15918.10S, 56u46902.30W).
Stratigraphic occurrence.?855 m (Fig. 2).
Remarks.?Leptomaria hickmanae may easily be distin-
guished from all other pleurotomariids presently known from
Seymour Island on the basis of its cyrtoconoid shape, strongly
convex whorls, well rounded periphery, very broadly ovate
(nearly circular) aperture, and broad selenizone situated just
below mid-whorl. It resembles L. amoena [Bajocian, France],
the type species of the genus in shape and general proportions
but is larger in size and appears to lack the reticulate surface
sculpture of that species.
Leptomaria hickmanae closely resembles Pleurotomaria
vacavillensis Hickman, 1976 [California, USA], which is here
reassigned to the genus Leptomaria. Leptomaria vacavillensis
appears to be higher spired than L. hickmanae, and also to
have a broader selenizone that is situated above rather than
FIGURE 10?Leptomaria hickmanae new species. 1, apertural; 2, dorsal; 3, apical, and 4, basal views of the holotype, USNM 467218. Locality K-423,
Seymour Island. Scale bar 5 2.0 cm, pb, peripheral bulge; pc, parietal callus; sz, selenizone.
758 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
below mid-whorl. Hickman (1976, p. 1099) noted that the
locality data accompanying the holotype of L. vacavillensis
??are not sufficiently precise to determine its stratigraphic
position, which is either lower Eocene or Upper Cretaceous.??
Similarities of this species to other Leptomaria would suggest
that L. vacavillensis lived during the Upper Cretaceous rather
than the Eocene.
LEPTOMARIA ANTIPODENSIS new species
Figure 11, Table 1
Diagnosis.?Shell small, conoidal, spire angle ,62u, anom-
phalous; whorls very weakly convex; aperture rhomboidal;
selenizone broad, well below mid-whorl; peripheral band
prominent; spiral sculpture weak to absent, axial sculpture
limited to growth striae of varying prominence.
Description.?Shell small for genus (maximum diameter
76.5 mm, minimum diameter 68.5 mm, height 75.1 mm), with
a tall, conical spire, consisting of four and one half preserved
teleoconch whorls. Base weakly convex, nearly flat, lacking an
umbilicus (Fig. 11.4). Spire angle ,62u. Spire evenly conical in
profile. Suture (Fig. 11.5) abutting previous whorl below
periphery of a pronounced peripheral bulge (Figs. 11.2, 11.5).
Protoconch and approximately first three teleoconch whorls
missing. Subsequent whorls conical, not gradate, very weakly
convex. Spiral sculpture weak to absent between suture and
selenizone, limited to weak threads and cords most conspic-
uous near peripheral bulge. Base without discernible spiral
sculpture. Selenizone moderately wide (Fig. 11.5; selenizone
width/suture to suture distance 5 0.19), flat to weakly convex,
situated below mid-whorl. Lunulae strongly concave, surface
sculpture unknown. Axial sculpture limited to growth striae of
varying intensity. Aperture narrowly ovate, long axis deflected
from the coiling axis by ,107u. Outer lip damaged, slit
moderately wide 4.5 mm, extending for less than one third
whorl. Shell relatively thin, thickest along columellar region
and base. Columella with a narrow, nacreous parietal callus
(Fig. 11.4).
Etymology.?Antipodes Greek?having the feet opposite, +
ensis, Latin?place of origin or habitat. 5 from the opposite
end of the world.
Types.?Holotype, USNM 467219, Upper Cretaceous,
Maastrichtian, Lopez de Bertodano Formation, Seymour
Island, Antarctic Peninsula (Fig. 1, Locality K-384;
64u16927.70S, 56u46948.30W).
Other material examined.?Paratype, USNM 468220, Up-
per Cretaceous, Maastrichtian, Lopez de Bertodano Forma-
tion, Seymour Island, Antarctic Peninsula (Fig. 1, Locality K-
46; 64u18956.70S, 56u48943.40W).
Stratigraphic occurrence.?K-384 5 703 m, K-46 5 666 m
(Fig. 2).
Remarks.?This new species is placed in the genus
Leptomaria with some reservation, as it lacks the strongly
convex whorls, rounded periphery and medial placement of
the selenizone characteristic of the type species. Leptomaria
antipodensis resembles L. larseniana in spire height, but its
shell is more conical, with whorls that are nearly straight-
sided. Unlike L. larseniana, the suture of L. antipodensis is
situated below a pronounced peripheral bulge, the selenizone
is closer to the shell periphery, and the spiral sculpture
appears to be much weaker, limited to the peripheral bulge
and adjacent areas. It is similar to Conotomaria sobralensis
(see below) in terms of size and shell profile but can be readily
distinguished from that species by the absence of an
umbilicus.
Genus CONOTOMARIA Cox, 1959
Type species.?Pleurotomaria mailleana d?Orbigny, 1843,
(by original designation). Cenomanian (Late Cretaceous) of
France.
Diagnosis.???Conical, anomphalous to broadly phanerom-
phalous; whorls flat or slightly sigmoidal in outline, last whorl
with sharply angular, often bulging periphery; selenizone at or
above mid-whorl, quite close to suture in some species, not
coinciding with an angulation; predominant ornament of
spiral cords. Jurassic and Cretaceous.?? (Cox, 1959, p. 238).
Range.?Middle Jurassic (Bajocian) to Paleocene (Thane-
tian; range extended by Pacaud, 2004, fig. 20). Cosmopolitan.
Remarks.?As with Leptomaria, Conotomaria has been
broadly defined to include a wide range of shell forms. The
type species of Conotomaria, C. mailleana, has a shell that is
large and broadly conical with whorls that are sigmoidal in
profile, and an angular, slightly bulging periphery, a
selenizone that is situated at or above mid-whorl, and a broad
umbilicus.
CONOTOMARIA SOBRALENSIS new species
Figure 12, Table 1
Conotomaria species A; STILWELL, ZINSMEISTER AND OLEI-
NIK, 2004, p. 25, pl. 4, fig. 1, 2.
Diagnosis.?Shell large, conical, spire angle ,68u, narrowly
phaneromphalous; whorls weakly convex; aperture trapezoi-
dal; selenizone broad, at mid-whorl; peripheral band promi-
nent; spiral sculpture of weak broad cords; base with only
axial growth striae.
Description.?Shell large for genus (holotype maximum
diameter 107.5 mm, minimum diameter 94.0 mm, height
108.1 mm), with a high conical spire consisting of eight
preserved teleoconch whorls. Base very weakly convex, with
narrow umbilicus (Fig. 12.4). Spire angle ,68u. Early whorls
conical, trochiform, final whorl broader. Suture (Fig. 12.2)
abutting previous whorl along base of peripheral bulge
(Fig. 12.2). Protoconch and first few teleoconch whorls absent
in holotype. Subsequent teleoconch whorls convex between
suture and selenizone, with maximum curvature just below the
suture but without producing an angled shoulder. Region
between selenizone and periphery straight. Spiral sculpture of
10?12 weak, broad cords between suture and selenizone, four
to five barely discernible cords between the selenizone and
periphery, and three to four stronger cords along the
peripheral bulge. Base with only axial growth lines and rugae.
Selenizone moderately broad (Fig. 12.2; selenizone width/
suture to suture distance 5 0.15), flat to weakly convex,
situated slightly below mid-whorl. Surface with weak lunulae
and without discernible spiral cords. Axial sculpture of fine
growth striae that become weakly rugose on final whorl, most
evident between selenizone and periphery, and along the base.
Aperture broadly rhomboidal, long axis deflected from the
coiling axis by ,117u. Outer lip worn, slit broad ,14 mm,
extending for about one quarter whorl. Inner lip thickest along
base and columellar region. Umbilicus deep and narrow,
forming a narrow, nacreous, parietal callus.
Etymology.?Named after the Sobral Formation, described
by Rinaldi (1977) as a part of the Marambio Group. Known only
from Seymour Island, it was named after Punta Sobral, better
known as Penguin Point on the maps of the Seymour Island.
Types.?Holotype, USNM 467221, Paleocene, Danian,
Sobral Formation, Seymour Island, Antarctic Peninsula
(Fig. 1, Locality A47; 64u16956.00S, 56u42958.90W).
Stratigraphic occurrence.?1,240 m (Fig. 2).
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 759
FIGURE 11?Leptomaria antipodensis new species. 1, apertural; 2, lateral; 3, apical, and 4, basal views of the holotype, USNM 467219. Locality K-384,
Seymour Island. 5, details of sculpture on lateral surface of the holotype; 6, apertural, and 7, apical views of the paratype. USNM 467220. Locality K-46,
Seymour Island. Scale bars 5 2.0 cm, pb, peripheral bulge; pc, parietal callus; s, suture; sz, selenizone.
760 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
Remarks.?This species is assigned to the genus Conoto-
maria on the basis of its broadly conical shell, sigmoidal whorl
profile, angular periphery with distinct bulge, and broad
umbilicus. It is closely allied with the Cretaceous type species,
C. mailleana from France but has slightly more convex whorls,
a broader, lower selenizone, and a slightly less developed
peripheral bulge. Of the Seymour Island pleurotomariids, it
resembles Leptomaria antipodensis (see above) in general form,
but may easily be distinguished by its broad umbilicus, and in
having the selenizone above rather than below mid-whorl.
CONOTOMARIA BAYERI new species
Figure 13, Table 1
Conotomaria species B; STILWELL, ZINSMEISTER AND OLEI-
NIK, 2004, p. 25?26, pl. 4, fig. 3, 4.
Diagnosis.?Shell small, conical, spire angle ,87u, narrowly
anomphalous; whorl profile weakly sigmoidal; aperture
trapezoidal; selenizone broad, at mid-whorl; peripheral broad
and weak; spiral sculpture of low broad cords also present on
base.
Description.?Shell small (maximum diameter 48.1 mm,
minimum diameter 40.9 mm, height 29.4 mm), thick
(1.0 mm on ramp of last whorl), with a broad, low conical
spire consisting of three preserved teleoconch whorls. Base
evenly convex, lacking an umbilicus (Fig. 13.4). Spire angle
,87u. Spire evenly conical, with pronounced peripheral bulge
(Figs. 13.1, 13.5). Suture (Fig. 13.5) abutting previous whorl
along base of peripheral bulge. Protoconch and first several
whorls absent in holotype. Subsequent teleoconch whorls
sigmoidal, slightly convex between suture and selenizone,
slightly concave between selenizone and peripheral bulge.
Spiral sculpture dominant, with seven to nine low, broad cords
between the suture and selenizone, five to six between the
selenizone and peripheral bulge. Base poorly preserved, with
vestiges of broad, shallow cords (estimated 20?25) and narrow
parietal callus (Fig. 13.4). Selenizone moderately broad
((Fig. 13.4; selenizone width/suture to suture distance 5
FIGURE 12?Conotomaria sobralensis new species. 1, apertural; 2, dorsal; 3, apical, and 4, basal views of the holotype, USNM 467221. Locality A47,
Seymour Island. Scale bar 5 2.0 cm, p, periphery; pb, peripheral bulge; s, suture; sz, selenizone; u, umbilicus.
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 761
0.20), weakly convex, situated at mid-whorl, with weak
lunulae and two to three spiral cords. Axial sculpture of fine,
oblique growth striae. Aperture narrowly rhomboidal, long
axis deflected from coiling axis by ,100u. Outer lip not
preserved, slit narrow ,2.7 mm, extending for less than one
third of a whorl. Parietal callus narrow, nacreous.
Etymology.?This species honors the late Dr. Frederick
Bayer, in recognition of his contributions to the systematics of
living Pleurotomariidae.
Types.?Holotype, USNM 467222, Paleocene, Danian,
Sobral Formation, Seymour Island, Antarctic Peninsula
(Fig. 1, Locality 9-2; 64u18934.90S, 56u43956.90W).
Stratigraphic occurrence.?1,167 m (Fig. 2).
Remarks.?This small species is very easily distinguished
from all other Pleurotomariidae on Seymour Island by its
comparatively small size, distinctly angulated appearance, and
prominent spiral sculpture. It also has a significantly thicker
shell, in proportion to the size. In outline and size, C. bayeri is
comparable to Pleurotomaria gurgitis Brongniart in Cuvier
and Brongniart, 1822 (p. 96, pl. 9, fig. 7A?B; d?Orbigny, 1843,
p. 249?250, pl. 192, fig. 4?6) from the Gault region, France,
but the whorls in C. bayeri are slightly more flush and less
convex, and the ornamentation is a bit weaker, compared with
P. gurgitis. The specimen figured in Brongniart (1822; see
FIGURE 13?Conotomaria bayeri new species. 1, apertural; 2, dorsal; 3, apical, and 4, basal views of the holotype, USNM 467222, Locality 9-2,
Seymour Island. 5, Details of sculpture on apertural surface of the holotype. Scale bar 5 2.0 cm, pb, peripheral bulge; pc, parietal callus; s, suture;
sz, selenizone.
762 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
especially pl. 9, fig. 7A), is higher spired, with no visible details
of a selenizone.
DISCUSSION
The Late Cretaceous and early Tertiary fossiliferous
deposits of Seymour Island contain the most nearly complete
boundary section in the southern hemisphere, and encompass
two major events with profound influence on the biota of the
region: the K/T extinction event, and the final breakup of
Gondwana. The effects of the massive terminal extinction
event that marked the end of the Cretaceous appear to have
been more gradual and less severe at high southern latitudes
(Zinsmeister et al., 1989). Indeed, Feldmann et al. (2005)
reported that there is no evidence that the brachyuran fauna of
southern Argentina was seriously affected by the K-T
extinction event. Many mollusks also survived the K-T
extinction event (Stilwell et al., 2004). Sohl (1987, p. 1105)
noted that Pleurotomariidae had a cosmopolitan distribution
during the Jurassic and Early Cretaceous but experienced a
marked reduction in the number of genera surviving into the
Tertiary. More recently, Pacaud (2004, fig. 20) documented
the survival of three genera into the Danian of northern
Europe. Pleurotomariid diversity at the species level was
greatest during the Cenomanian, declined rapidly by the
Turonian, and remained relatively stable during the remainder
of the Cretaceous (Sohl, 1987, p. 1105, fig. 10).
During the Late Cretaceous, the southern continents were
separated by shallow seas extending from the southern tip of
South America to eastern Australia. The resulting shallow
shelf, cool-temperate seaway, extending along the western
margin of Antarctica, was named the Weddelian Province by
Zinsmeister (1979) based on a highly endemic (.50%
endemism) molluscan fauna. As a result of the final
fragmentation of Gondwana, the shelf regions of Antarctica,
southern South America, and Australia were increasingly
isolated during the early Tertiary. The combination of
extinction events at the end of the Cretaceous and the
geographic isolation of the continents set the stage for rapid
diversification of many components of marine molluscan
faunas in this region during the early Paleocene (Oleinik and
Zinsmeister, 1996).
Including the species described in this paper, the known
species richness of the pleurotomariid fauna of Seymour
Island has increased to seven, two species of Leptomaria of
FIGURE 14?Paleogeography of the Antarctic and the Weddelian Province during the Late Maastrichtian?Early Paleocene, showing locations of
deposits containing pleurotomariid fossils (See Table 2 for list of pleurotomariid taxa occurring at these localities). &?Seymour Island, Antarctica. Late
Maastrichtian, Lopez de Bertodano Formation, Danian, Sobral Formation (herein).??Late Maastrichtian, Miria Formation, Northwestern Australia
(Darragh and Kendrick, 1994). &?New Zealand, Senonian, Amuri Group (Wilckens, 1922). N?Southern India, Campanian-Maastrichtian, Arrialoor
Group (Stoliczka, 1868). .?Northwestern Madagascar, Lower Albian, Mahajanga Basin, (Collignon, 1959; Kiel, 2006). ?West Central Argentina,
Jurassic and Early Cretaceous, (Stanton, 1901; Weaver, 1931; Feruglio, 1936).
HARASEWYCH ET AL.?ANTARCTIC CRETACEOUS AND PALEOCENE GASTROPODS 763
Late Maastrichtian age, and three species of Leptomaria and
two species of Conotomaria of Danian age. Given that
molluscan fossils of Late Cretaceous and Early Paleocene
age on Seymour Island are well preserved and moderately well
collected (Stillwell et al., 2004), it is likely that this represents
but a subset of the true species richness.
The Seymour Island Late Cretaceous pleurotomariid fauna
is comparable in species richness and generic composition to
the coeval faunas of Australia (Darragh and Kendrick, 1994),
New Zealand (Wilckens, 1922), and southern India (Stoliczka,
1868), less so to the older, more diverse faunas of southern
South America (Weaver, 1931), and Madagascar (Delpey,
1948; Collignon, 1959; Kiel, 2006) (Fig. 14). Comparisons of
the Danian pleurotomariid fauna to regional contemporane-
ous faunas are not possible, since Danian Stage pleurotomar-
iid records are presently known only from northern Europe
(Hickman, 1976, p. 1092, text-fig. 2; Pacaud, 2004, p. fig. 20).
However, there does appear to be an increase in the species
richness of the pleurotomariid fauna of Seymour Island during
the Paleocene. The pattern of diversification immediately
following the K/T extinction in Antarctic faunas has been
previously observed in the gastropod genus Seymourosphaera
(Oleinik and Zinsmeister, 1996) as well as in palynomorphs
(Askin, 1988), diatoms, and silicoflagellates (Harwood, 1988).
The pleurotomariid fauna of the Late Maastrichtian Miria
Formation of Northwestern Australia, which was contempo-
raneous with the Lopez de Bertodano Formation of Seymour
Island, consisted of two species of Conotomaria and a single
species of Leptomaria (Darragh and Kendrick, 1994). The
ratio of Conotomaria to Leptomaria sampled in this fauna was
25:1 (n 5 390) (Darragh and Kendrick, 1994, table 1).
However, given the tentative generic assignments for the most
common Seymour Island species?L. antipodensis (herein), C.
(?) cypsela (Darragh and Kendrick, 1994, p. 15) and L.
perancisa (Darragh and Kendrick, 1994, p. 20), the apparent
difference in generic composition between the two faunas may
be an artifact of our currently accepted taxonomy. Alterna-
tively, it may indicate that patterns of fine-scale allopatry,
possibly on the basis of depth or substrate type, are similar to
those evident in Recent pleurotomariid faunas. Although up
to four species of living pleurotomariids may be collected on a
single sub dive, they are, in fact, allopatric, occurring at
different depths and on different substrates. These patterns are
both consistent and dramatic (Harasewych, 2002, p. 274, fig.
12) and may also have been present in Late Cretaceous faunas.
The sediment type, lack of an associated hard substrate
fauna, and co-occurrence of a number of soft-substrate
bivalves and gastropods, indicate that Late Maastrichtian
and Danian Pleurotomariidae from the Seymour Island
inhabited fine-grained sandy and silty substrates of the outer
continental shelf, a habitat more similar to that of Permian
(Batten, 1958) than Recent pleurotomariids, which inhabit
hard substrates and steeply sloped walls along the outer
continental shelf and upper continental slope (Harasewych,
2002). Batten (1958) hypothesized that environments with
high levels of fine suspended sediments resulted in dwarfing,
based on studies of Paleozoic pleurotomarioideans. However,
Seymour Island Pleurotomariidae are of larger size, and more
similar to the Recent species than to the smaller Paleozoic
forms. The shift in habitat from shallow water to deeper water
was evident by the early Eocene (Hickman, 1976, p. 1093).
Kanno (1961, p. 115) hypothesized that this shift reflected an
ontogenetic pattern, while Hickman (1976, p. 1093) consid-
ered it more likely that the shift was due to range constriction
and elimination of the shallow-water forms. The elimination
of the shallow-water Pleurotomariidae may be related to
competition with rapidly diversifying groups of other shelf
mollusks following the K/T extinction event. Direct observa-
tions from the submersibles and in aquaria, supplemented by
gut content analysis, indicate that Recent Pleurotomariidae
are primarily spongivorous (Harasewych et al., 1988).
However, when kept in aquaria under stressed conditions,
pleurotomariids consumed a variety of organisms (Arakawa et
al., 1978; Hickman, 1984; Harasewych, 2002), raising the
possibility that, in spite of today?s restricted diet and highly
specialized radula (Hickman, 1981, 1984; Harasewych, 2002),
they may have occupied a broader trophic niche in the past.
Radley (1992, p. 173) deduced that Jurassic pleurotomariids
lived in warm, shallow-water, photic habitats, and fed at least
partly on algae.
In terms of size and morphology, many of the Seymour
Island species resemble more closely taxa from the Jurassic of
Europe and southern South America than more geographi-
cally proximal Late Cretaceous species. Leptomaria hickma-
nae, for example, more closely resembles L. amoena [Jurassic,
France], Pleurotomaria vacavillensis Hickman, 1976 [Creta-
ceous, California, USA] and L. tardensis [Lower Cretaceous,
Argentina] than contemporaneous southern hemisphere spe-
cies. Similarly, Early Paleocene L. stilwelli new species, closely
morphologically resembles L. leufuensis [Late Jurassic, Ar-
TABLE 2?Summary of pleurotomariid occurrences in the Late
Cretaceous/Paleocene of the Weddelian Province. See Figure 46
for locations.
& Seymour Island, Antarctica. (Sobral Formation Paleocene [Danian]
(Wilckens, 1910; herein)
Conotomaria sobralensis Harasewych Oleinik and Zinsmeister (herein)
Leptomaria larseniana (Wilckens, 1910)
Leptomara stillwelli Harasewych Oleinik and Zinsmeister (herein)
Conotomaria bayeri Harasewych Oleinik and Zinsmeister (herein)
Leptomaria seymourensis Harasewych Oleinik and Zinsmeister (herein)
(Lopez de Bertodano Formation?Late Cretaceous [Late Maastrichtian]
(herein)
Leptomaria hickmanae Harasewych Oleinik and Zinsmeister (herein)
Leptomaria antipodensis Harasewych Oleinik and Zinsmeister (herein)
? Northwestern Australia?Miria Formation?Late Cretaceous [Late
Maastrichtian] (Darragh and Kendrick, 1994)
Conotomaria? cypsela Darragh and Kendrick, 1994
Conotomaria minacis Darragh and Kendrick, 1994
Leptomaria perancisa Darragh and Kendrick, 1994
& New Zealand?Amuri Bluff?Late Cretaceous [Santonian] (Wilckens,
1922)
Pleurotomaria maoriensis Wilckens, 1922
Pleurotomaria woodsi Wilckens, 1922N Southern India?Ootatoor Group?Late Cretaceous [Cenomanian]
(Stoliczka, 1868)
Pleurotomaria glabella Stoliczka, 1868
Pleurotomaria loricatula Stoliczka, 1868
Leptomaria indica (Forbes, 1856)
. Madagascar?Ambaramaninga?Lower Cretaceous [Albian]
(Collignon, 1949; Kiel, 2006)
Leptomaria magneti Collignon, 1949
Argentina (Stanton, 1901; Weaver, 1931; Feruglio, 1936)
Pleurotomaria? andina Feruglio, 1936. Late Cretaceous [Senonian],
Arroyo Calafate
Pleurotomaria cf. provincialis d?Orbigny, 1842. Early Cretaceous
[Valanginian] Quintuco Fm
Pleurotomaria gerthi Weaver, 1931. Early Cretaceous [Barremian],
Agrio Fm
Pleurotomaria cf. jaccardi Picte and Campiche, 1861. Early Cretaceous
[Barremian], Agrio Fm
Pleurotomaria tardensis Stanton 1901. Early Cretaceous [Barremian],
Belgrano Beds
764 JOURNAL OF PALEONTOLOGY, V. 83, NO. 5, 2009
gentina] and L. daityai [Late Jurassic, India]. Those similarities
support the conclusion of Stilwell et al. (2004) concerning the
breakup of the Weddelian Province by the end of Cretaceous
and interrupted connections with the Australia-New Zealand
region. It may also indicate that Antarctic Cretaceous and
Early Tertiary Pleurotomariidae were remnants of a once
cosmopolitan group that was widespread in the Jurassic and
had their habitats fragmented as a result of the progress in the
breakup of Gondwana.
ACKNOWLEDGMENTS
We are grateful to Dr. Ru?diger Bieler for translating the
original description of Pleurotomaria larseniana. Thanks are
due to Dr. Shiladri Das for many informative discussions on
the systematics and ecology of Mesozoic Pleurotomariidae,
particularly from the Kutch region of India. We appreciate
and gratefully acknowledge the many helpful comments and
insights of the referees, Dr. Steffen Kiel and Dr. Andrzei
Kaim, as well as of the editors, Dr. Peter Harries and Dr.
Richard Lupia, which markedly improved this paper. The field
work on Seymour Island was supported by the National
Science Foundation grant OPP 93-16034.
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