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A new species of the rare batomorph genus Hypolophodon (?latest
Cretaceous to earliest Paleocene, Argentina)
Alberto Luis Cione, Marcelo Tejedor and Francisco Javier Goin
With 5 figures
Cione, A.L., Tejedor, M. & Goin, F.j. (2013): A new species of the rare batomorph genus Hypolo-
phodon (?latest Cretaceous to earliest Paleocene, Argentina). – N. Jb. Geol. Paläont. Abh., 267: 1–8;
Stuttgart.
Abstract: Isolated teeth of a new species of the rare batomorph genus Hypolophodon were found
in Paleocene beds of the Lepán Formation (Maastrichtian-Paleocene) of southern Argentina. The
new species H. patagoniensis differs from the type species H. sylvestris in the absence of an occlusal
tranverse crest on the crown of unworn teeth and of a broad and rounded central uvula on the lingual
face of the crown; and in the presence of a lower boundary of the enameloid smooth on all crown
faces, many expanded basoapically striae on all sides of the root, and a deep root. It differs from the
Eocene species H. dockery in the larger size, the less widely separated root branches, the presence
of root foraminae or striae, the absence of uvula, and the deeper crown. The new species material,
the two teeth from Jaguel Formation, and an indeterminate tooth of Hypolophodon from the Lower
Cenozoic of Chile represent the sole records of the genus in the Southern Hemisphere. The shark
fauna helped to date the bearing beds.
Key words: Batomorphii, Hypolophodon, Argentina, South America, Paleocene, Cenozoic.
1. Introduction
During the Late Cretaceous and Early Paleogene
different batomoph clades suffered extinctions
and diversications (KriweT & BenTon 2004).
Hypolophodon has been considered to be one of the
batomomorphs that replaced the taxa that became
extinct during the Cretaceous-Paleogene event. In South
America, there are few relatively recent descriptions of
Maastrichtian to Danian elasmobranchs (i.e. reBouçAs
& sAnTos 1956; sChAeFFer 1963; CAppeTTA 1975, 1991;
ArrATiA & Cione 1996; GonzáLez riGA 1999; GAyeT
et al. 2001; BoGAn & AGnoLin 2010; BoGAn & GALLinA
2011). Additionally, there here are very few records
of the batomorph genus Hypolophodon CAppeTTA,
1980 around the world, especially from the Southern
Hemisphere (see Bourdon 1999a). In this contribution,
a new species of Hypolophodon is described from
the latest Cretaceous and the earliest Paleogene of
southern Argentina.
2. Geological setting
Most of the material here described comes from a
section of the Lepán Formation (LesTA & FereLLo
1972) located in the Estancia “26 de Mayo,” owned by
the Grenier family (42°46’ S and 69°51’ W), about 20
km to the west of Paso del Sapo, near the Río Chubut,
northwestern Provincia del Chubut, Argentina (Fig. 1).
The Lepán Formation is maximal 370 m thick,
marine to proximal marine siliciclastic unit, which
crops out discontinuously in northwestern Chubut
©2012 E. Schweizerbart ’sche Verlagsbuchhandlung, Stuttgart, G ermany www.schweizerbart.de
DOI: 10.1127/0077-7749/2012/0293 0077-7749/2012/0293 $ 2.00
N. Jb. Geol. Paläont. Abh. 267/1, 1–8 Article
Published online December 2012
eschweizerbart_xxx
2 A.L. Cione et al.
Province of southern Argentina (oLivero et al. 1990;
oLivero & MedinA 1993; sCAsso et al. 2012). Along
the Río Chubut, it is recognized from Piedra Parada to
Estancia T. Ibarra (formerly Estancia Lepán; peTers-
en 1946; FeruGLio 1949; MedinA et al. 1990; oLivero
et al. 1990).
The Lepán Formation is mainly composed of
massive and heterolithic mudstones with several in-
tercalations of sandstone lenses and coquinas with
well preserved molluscan faunas of Maastrichtian
and Paleocene age (sCAsso et al. 2012). Sandstones
are massive, or display parallel or cross-bedding. Oc-
cassionally they show well preserved bioturbation of
the Skolithos-Cruziana-like ichnofacies and contain
phosphatic concretions (pereirA & sCAsso 2002). The
complete unit was deposited in a shallow epeiric sea
and the sandstones were interpreted as bars and shoals
accumulated in a shoreface environment (spALLeTTi
1996). The Lepán Formation overlies the Late Cre-
taceous Paso del Sapo Formation (Campanian-Maas-
trichtian; pApú et al. 1988) and underlies the Eocene
strata of the Laguna del Hunco Series.
The unit can be divided into three sections (Me-
dinA et al. 1990). These sections can be recognized
in the Estancia “26 de Mayo” prole, where 65 m of
exposures represent the Cretaceous-Paleocene transi-
tion. The lower 12 m are characterized by brown mud-
stones with concretions and rare heterolithic bedding,
and rusty-brown massive sandstones. It is conformably
overlaid by a 5 m thick packet of massive sandstones of
the middle section, with large carbonatic concretions,
bivalves, gastropods, callianassid crabs, and shark and
ray teeth. The upper section is mainly composed of
unconsolidated to slightly consolidated mudstones
and exposure is poor. The uppermost bed is a strongly
bioturbated, fossiliferous sandstone with abundant
Fig. 1. Location map.
Fig. 2. Prole at Estancia “26 de mayo.”
eschweizerbart_xxx
A new species of the rare batomorph genus Hypolophodon 3
Ophiomorpha and Thalassinoides. In the farm Estan-
cia “Don Félix”, owned by Mr. CreTTon, a few kilo-
meters west of Estancia “26 de Mayo,” one Hypolo-
phodon tooth was found. The Lepán Formation here
conformably underlies possible early Paleocene conti-
nental strata composed mainly by gray sandstones and
mudstones, including abundant leaf impressions and
volcaniclastic agglomerates (Fig. 2; peTersen 1946;
ArAGón & MAzzoni 1997). The middle section of
Lepán Formation is also exposed at Estancia “Don
Félix”, and the fossil sh material is well represented,
as in the Grenier farm.
Apparently, a continuous Cretaceous-Cenozoic
transition is represented in the Grenier section, with-
out any apparent unconformity. The lower section of
the Lepán Formation was assigned to the Maastrich-
tian because of some of the invertebrate fossils (Ostrea
cf. rionegrensis, Pterotrigonia (Rinetrigonia) wind-
hausenia, Pacitrigonia patagonica, Tagelus gratus,
Pugnelus sp., Struthioptera pastorei; see MedinA et al.
1990; oLivero et al. 1990).
The middle and upper sections were assigned to
the Paleocene (MedinA et al. 1990). They include the
bivalve Meretrix chalcedonica, among others, which
also occur in the Danian Salamanca Formation. In
the upper section, Pycnodonte miradonensis pre-
dominates, which also is known from the Salamanca
Formation (MedinA et al. 1990). There are additional
invertebrates that support a Paleocene age.
The sh material described here comes from the
middle section. The ichthyofauna includes isolated
teeth of teleosteans and neoselachians and it is in
agreement with a Cenozoic age because A) there are
neither specimens of families or genera that became
extinct before the Cretaceous-Paleocene boundary
(e.g. Hybodontidae, Acrodontidae, Anacoracidae,
Polyacrodontidae, Sclerorhynchidae, Ptychodontidae,
Rhombodontidae, Scapanorhynchus, Igdabatis), nor
of those families that are relatively abundant in the
Cretaceous (Palaeospinacidae, Orthacodontidae, Cre-
toxyrhinidae) in an ichthyofauna with predominance
of Carcharias, and (B) several teeth of a new species
of the batoid genus Hypolophodon have been record-
ed. Until recently, Hypolophodon was only known
from the Paleocene-middle Eocene (but see below).
Crab and foraminifera remains do not include any
denite Cretaceous taxa. Besides, there are no records
of Cretaceous marine tetrapods such as plesiosaurs or
mosasaurs. The same level that the new species of Hy-
polophodon yielded the oldest Cenozoic mammal of
South American was reported (Goin et al. 2006).
3. Systematic palaeontology
Subclass Elasmobranchii BonApArTe, 1838
Order Myliobatiformes CoMpAGno, 1973
Family indet.
Genus Hypolophodon CAppeTTA, 1980
Hypolophodon patagoniensis nov. sp.
Figs. 3-4
2010 cf. Pseudohypolophus mcnultyi BoGAn & AGnoLin,
p. 184
2011 Hypolophodon sylvestris BoGAn & GALLinA, p. 59
Etymology: The species name is derived from the South
American region called Patagonia.
Holotype: LIEB-PV 1600. Anterior tooth. Crown width:
6.4, crown length: 4.6, ratio of crown width/length: 1.4, total
height: 4.4. Estancia “26 de Mayo” (measurements in mm).
Repository: Laboratorio de Investigaciones en Evolución y
Biodiversidad, Facultad de Ciencias Naturales, Sede Esquel,
Universidad Nacional de la Patagonia “San Juan Bosco,”
Sarmiento 849, 9200 Esquel, Chubut, Argentina (LIEB).
Referred material: LIEB-PV 1601. Fragmentary tooth.
Estancia “26 de Mayo.” LIEB-PV 1602. Lateral tooth.
Crown width: 2.2, crown length: 2.0, rate crown width/
length: 1.1, total height: 2.0. Estancia “26 de Mayo.” LIEB-
PV 1603. Anterior tooth. Crown width: 4.8, crown length:
4.0, rate crown width/length: 1.2, total height: 3.4. Estancia
“Don Félix.” LIEB-PV 1604. Anterior tooth. This tooth
was sectioned (Fig. 4). Crown width: 5.2, total height:
3.3. Estancia “26 de Mayo.” LIEB-PV 1605. Fragmentary
lateral tooth. Crown width: 2.1, crown length: 2.0, rate
crown width/length: 1.05. Estancia “26 de Mayo.”
Type locality and horizon: Estancia “26 de Mayo” (LIEB-
PV 1600, 1601, 1602, 1604, 1605), and Estancia “Don
Félix” (LIEB-PV 1603), northwestern Chubut Province,
central Patagonia, Argentina (Fig. 1). Middle section of
Lepán Formation. Early Paleocene. Collectors: FrAnCisCo
Goin and MArCeLo Tejedor. Two other teeth, reported as
Hypolophodon sylvestris by BoGAn & GALLinA (2011) come
from Maastrichtian beds of the Jagüel Formation at Cerro
Dientes, provincia de Río Negro Argentina.
Diagnosis: Species of Hypolophodon that differs from the
type species (H. sylvestris) in the absence of an occlusal
tranverse crest on the crown of unworn teeth and of a
broad and rounded central uvula on the lingual face of
the crown; and in the presence of the lower boundary of
the enameloid which is smooth on all crown faces, many
expanded basoapically striae on all sides of the root (not
only the lingual one as in H. sylvestris), and a deep root.
H. patagoniensis differs from another putative species (H.
dockery) in the larger size, the less widely separated root
branches, the presence of root foraminae or striae, the
absence of uvula, and the deeper crown.
eschweizerbart_xxx
4 A.L. Cione et al.
Description: The teeth have a strongly grinding
morphology. The crown is deep. The crown oral face is
smooth and usually almost at, without any transverse crest.
In the holotype the oral face is slightly convex. The crown
width/length ratio ranges from 1.4 to 1.05. The smaller ratio
of 1.4 probably corresponds to anterolateral teeth and those
near equant probably represent laterals (see CAppeTTA 1987).
LIEB-PV 1600 presents a clear hexagonal contour, but the
other well preserved teeth are rounded or even quadrangular
in shape. The lower boundary of the enameloid is always
smooth on all crown sides. The crown is broader at the level
of the occlusal face than at the level of the collar and slightly
overhangs the root (Fig. 3). There is no central uvula on the
lingual face of the crown. There is a constriction all around
the teeth in the collar.
The root is deep, bilobate, with a well dened, narrow
labiolingual groove. There is one foramen in the bottom of
the labiolingual groove. Most specimens display numerous
expanded basoapically foramina on all root faces (LIEB-PV
1600, 1602, 1603; see also BoGAn & GALLinA 2011, g. 2).
One tooth was sectioned lengthwise (LIEB-PV 1604;
see also BoGAn & GALLinA 2011). The root show large
vascular spaces. The crown is mostly made up of trabecular
dentine in the crown (Fig. 4). There is no pulp cavity.
The upper part of the crown shows the distinct pattern of
radiating dentine that denes the boundary between the
clusters of orthodentine. We have not seen any structures
in the enameloid.
4. Discussion
The combination of a smooth and almost at crown,
smooth crown faces, the reduced width, the ratio be-
tween root and crown height, the single basal groove
in root, the basoapical elongated foramina in the
root separates the present material from other bato-
morphs such as fossil and extant Torpediniformes,
Pristiformes, Rhiniformes, Rhynchobatiformes, Raji-
formes, and Myliobatiformes and the extinct Sclero-
rhynchoidei, Platyrhinidae, Distobatidae, Archaeono-
batidae, Hypsobatidae, Aegyptobatus, Myledaphus,
Parapaleobates, Protoplatyrhina, Segmetia, Renpe-
tia, Squatirhina, and Ptychotrygon (extant taxa ac-
cording to MCeAChrAn et al. 1996; fossils according
to CAppeTTA 1987, 1992; werner 1989; deLsATe &
CAndoni 2001).
Fig. 3. Hypolophodon patagoniensis sp. nov. Anterior
teeth. LIEB-PV 1600: 1 – lingual view; 2 – labial view; 3
– lateral view; 4 – occlusal view; 5 – basal view. Young
individual, LIEB-PV 1603: 6 – lingual view; 7 – labial view;
8 – occlusal view; 9 – basal view. Scale bar equals 2 mm.
Fig. 4. Hypolophodon patagoniensis sp. nov. LIEB-
PV 1604: Ground section of an anterior tooth showing
trabecular dentine in the crown. Scale bar equals 1 mm.
eschweizerbart_xxx
A new species of the rare batomorph genus Hypolophodon 5
The material resembles species of the Cretaceous
Pseudohypolophus and the Cretaceous-Eocene Hypo-
lophodon genera. Pseudohypolophus includes the spe-
cies P. mcnultyi (CAppeTTA & CAse, 1975) and P. ellip-
sis CAse et al., 2001. The genus ranges in age from the
Barremian to Maastrichtian of North America, Europe,
and South America (Bourdon 1999b) and was consid-
ered to be Rhinobatoidei incertae sedis by CAppeTTA
(1987). However, there are other opinions (see Bour-
don 1999b). Reports from Europe include the Barre-
mian of Teruel, Spain (KriweT 1999). Reports from
the United States include the Aptian to Cenomanian
of North Carolina (CAppeTTA & CAse 1975) and Texas,
United States (weLTon & FArish 1993), the Turonian
of Nebraska and Kansas, United States (KirKLAnd
1989; everhArT et al. 2003; sTewArT & MArTin 1993),
the Santonian-Campanian of Mississippi (MAnninG &
doCKery 1992), Santonian of Alabama (Meyer 1974),
Campanian of New Jersey (LAuGiniGer 1986), Georgia
(sChwiMMer 1986), and North Carolina (roBB 1989, as
Rhombodus levis), and the Maastrichtian of Maryland
(hArTsTein et al. 1999).
Hypolophodon is assigned here to an indetermi-
nate family of Myliobatiformes. Several putative spe-
cies of Hypolophodon were recognized. The species
Hypolophodon sylvestris (whiTe 1931) was reported
from the Danian of New Jersey (The pALeoBioLoGy
dATABAse 2008) and Belgium (herMAn 1975), Thane-
tian of northwestern United States (CvAnCArA & ho-
GAnson 1993), the Thanetian and lower Eocene of Eng-
land, Belgium, and France (KeMp et al. 1990; BAuT &
GenAuLT 1995; duTheiL et al. 2002), the lower Eocene
of the Chesapeake region, United States (KeMp et al.
1990; Bourdon 1999a, b), the middle Eocene of Vir-
ginia, United States, and Uzbekistan (wiLLiAMs 1999;
CAse et al. 1996). Hypolophodon dockery (CAse, 1994),
was formerly assigned to genus Platyrhina and it is
only known from the early Eocene Bashi Formation
of Mississippi (CAse 1994). Another species referred
to Hypolophodon, H. malembensis, from the Eocene
and Miocene of Africa, does not appear to belong to
the genus (see MurrAy et al. 2010).
The Patagonian material resembles the Cretaceous
genus Pseudohypolophus on the smooth occlusal
crown surface, absence of uvula on the lingual face of
the crown, and the lower boundary of the enameloid
usually not irregular on any crown face. However, it
clearly differs in the crown being broader at the level
of the oral surface than at the level of the collar and
not overhanging strongly the root, in having numer-
ous apicobasally elongated foramina on all the crown
faces, and because there is no pulp cavity.
The Patagonian material resembles the genus Hy-
polophodon in its size, the crown being broader at the
level of the oral face than at the level of the collar and
not overhanging strongly the root, and especially, by
its histology. CAppeTTA (1987) and johnson & LuCAs
(2002) indicated that histology is a fundamental char-
acter for distinguishing Pseudohypolophus from Hy-
polophodon.
Hypolophodon patagoniensis differs from the Pa-
leocene and Eocene species H. sylvestris in several
features: the absence of an occlusal tranverse crest on
the crown of unworn teeth and of a broad and round-
ed central uvula on the lingual face of the crown; in
the presence of the lower boundary of the enameloid
smooth on all faces (see for example, teeth of H. syl-
vestris with blunt and broad vertical folds in the base
of enamel in CAppeTTA (1987, g. 140C) and KeMp et
al. (1990, pl. 10, g. 11), the numerous basoapically
elongated striae on all faces of the root (not only on the
lingual one as in H. sylvestris), and the deeper root. It
also differs from the putative Eocene species H. dock-
ery in the larger size, the less widely separated root
branches, the presence of root foraminae or striae, the
absence of uvula, the deeper crown (see CAse 1994).
In northern Patagonia, from Maastrichtian beds of
the Jagüel Formation, BoGAn & AGnoLin (2010) iden-
tied a tooth as cf. Pseudohypolophus mcnultyi. The
following year, BoGAn & GALLinA (2011) reported this
specimen plus a new one to Hypolophodon sylvestris.
We assign both teeth to Hypolophodon patagoniensis
on the basis of their morphology. In Chile, Muñoz et
al. (2007) had gured a specimen under the name of
Dasyatidae indet. (mentioning the similarity to Hy-
polophodon teeth) from putative upper beds of the
Quiriquina Formation (Late Cretaceous). The mate-
rial clearly belongs in Hypolophodon. CArLos Muñoz
(2008, pers. comm.) presently believes that these beds
are Cenozoic in age.
Pseudohypolophus had been reported from Bar-
remian to Maastrichtian strata and Hypolophodon
from latest Maastrichtian to Eocene strata. Both gen-
era present a grinding-type dentition as adaptation to
hard-shelled prey (KriweT & BenTon 2004). Pseu-
dohypolophus became extinct along numerous other
taxa with grinding dentitions (Hypsobatis, Pucabatis,
Rhombodus, and Youssoubatis) at the end of the Creta-
ceous and was replaced by other taxa with the similar
adaptations (e.g., Hypolophodon, Hypolophites, Myli-
obatis) (CAppeTTA 1992; KriweT & BenTon 2004). Re-
markably, the report of Hypolophodon from the Jagüel
eschweizerbart_xxx
6 A.L. Cione et al.
Formation (BoGAn & GALLinA 2011) is the sole record
of the genus from Cretaceous beds. The occurrence of
the genus before the great extinction of the K-P bound-
ary is curious.
Species of Pseudohypolophus and Hypolophodon
inhabited shallow waters. However, we do not know
if also occupied deeper waters. Other than one doubt-
ful report from relatively low latitude areas (CAppeTTA
1987), Hypolophodon appears to have been restricted
to middle palaeolatitudes (Fig. 5). It has not been re-
ported from neither equatorial nor polar areas. The
Patagonian and Chilean material are the sole records
of Hypolophodon from the Southern Hemisphere. The
southern South American specimens might indicate
that the genus would have a bipolar distribution, with
one or two northern species and one southern species.
Acknowledgements
We would like to thank the Geologists’ Association of
London and the Fundación Antorchas of Buenos Aires for
a grant to AC to study collections in Europe. The Natural
History Museum of Los Angeles County, Natural History
Museum of London, California Academy of Sciences of
San Francisco and American Museum of Natural History
of New York, for permission to examine fossil batoid
material (among others, Pseudohypolophus mcnultyi and
Hypolophodon sylvestris specimens). The Agencia Nacional
de Promoción Cientíca y Tecnológica, Consejo Nacional
de Investigaciones Cientícas y Técnicas and Universidad
Nacional de La Plata for nancial support. AGusTín viñAs,
LuCiAno rAsiA, and MA rCeLA ToMeo for the illustrations.
CArLos Muñoz for valuable information. Last but not least,
jürGen KriweT and ChArLie underwood, the two referees,
which greatly contributed to improve the manuscript.
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Manuscript received: July 1st, 2009.
Revised version accepted by the Stuttgart editor: July 20th,
2012.
Addresses of the authors:
ALBerTo Luis Cione (corresponding author), FrAnCisCo
jAvier Goin, División Paleontología de Vertebrados, Museo
de La Plata, 1900 La Plata, Argentina;
e-mails: acione@museo.fcnym.unlp.edu.ar, fgoin@museo.
fcnym.unlp.edu.ar
MArCeLo Tejedor, Laboratorio de Investigaciones en
Evolución y Biodiversidad, Facultad de Ciencias Naturales,
Sede Esquel, Universidad Nacional de la Patagonia “San
Juan Bosco,” Sarmiento 849, 9200 Esquel, Chubut,
Argentina;
e-mail: mtejedor@lieb.org.ar
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