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A GIANT SERRATED - TOOTHED ALOPIAS
In around 2002. rumours were circulating about
another large species of lamniform shark
with serrated teeth from the Miocene
of South Carolina. Some teeth
were dismissed as possibly
being upper laterals
of one of the
known giant
sharks ;
Alopias grandis Early Miocene, Malta.
RECENT THRESHER SHARKS
Thresher sharks (Alopias spp.) are readily identified by
their elongated caudal fins, that allow them to both
swim rapidly and stun prey.
There are three Recent species of thresher with World
Wide [WW]or Indo-Pacific [IP] distribution.
Alopias vulpinus WW – surface waters.
Alopias pelagicus IP– surface waters.
Alopias superciliosus WW – deep water.
All three Recent species have small,
fairly homodont dentitions.
A new giant species of thresher shark
from the Miocene of the
United States
David J. Ward1 & Bretton W. Kent 2
1Department of Earth Sciences, The Natural History Museum, London, SW7 5BD, U.K.
2 College of Computer, Mathematical and Natural Sciences, University of Maryland, College Park, MD 20742 USA
REFERENCES
DIESTER-HAASS, L., K. BILLUPS, D. R. GROCKE,
L. FRANCOIS, V. LEFEBVRE, &K. C. EMEIS. 2009.
Mid-Miocene paleoproductivity in the Atlantic Ocean and
implications for the global carbon cycle,
Paleoceanography, 24: 1209.
SAVIN, S. M., ABEL L., BARRERA, E., HODELL, D.,
KELLER, G., KENNETT, J. P., KILLINGLEY, J.,
MURPHY, J. M. &VINCENT, E. 1985. The evolution
of Miocene surface and near-surface marine temperatures:
oxygen isotopic evidence, GSA Memoir, 163: 49-102
KENT, B. W. & WARD, D. J. in press. Addendum: A
new species of Miocene giant thresher shark (Alopias)
with serrated teeth. In: S. Godfrey (ed.), The geology and
vertebrate paleontology of Calvert Cliffs (Chesapeake
Group), Maryland, USA. Smithsonian Contributions to
Paleobiology.
HISTORICAL BACKGROUND
In 1942, Leriche described a large species of thresher shark
from the Neogene of the USA. He figured two specimens
which he named Alopecias (= Alopias) grandis
One tooth, the holotype, was from the Miocene Calvert
Formation of Nomini Cliffs, Westmorland County,
Virginia. The second, a somewhat larger specimen, was
reworked from the Neogene of the Charleston area
This species, although not particularly rare, has received
little attention in the subsequent literature.
Bretton W. Kent [bkent@umd.edu] David J. Ward
[djw@nhm.ac.uk]
FOSSIL THRESHER SHARKS
The oldest known fossil teeth of Alopias are from the early
Eocene: Alopias crochardi Ward 1978, from the London
Clay and Alopias denticulatus Cappetta 1981, from the
Moroccan phosphates. The latter has small lateral cusps, a
feature still present in juvenile teeth of Alopias vulpinus.
By the late Eocene, teeth resembling those of the Recent A.
vulpinus and A. superciliosus can be picked out, suggesting
that both lineages had already separated.
Tooth of the holotype of the new giant serrated thresher shark.
Left lower jaw, of Alopias vulpinus, lingual view, showing incipient lateral cusplets.
It is unlikely that the new giant
thresher shark possessed an
elongated dorsal tail lobe seen
in the Recent species. As the
dentition is converging on a
great white shark and its size
was similar or larger, it is
reasonable to suppose that the
body outline was similar.
The plastic model (left)
supposedly of a thresher but
with a much shortened tail, by
chance, corresponds to this
body outline.
Teeth of Alopias spp., from the late Eocene of Kazakhstan.
MIOCENE SHARK GIGANTISM
In the late Early and Middle Miocene there was burst of
gigantism in a number of unrelated species of shark. This
event corresponded with the warmest interval of the
Neogene, the "middle Miocene climatic optimum", an
interval of high oceanic productivity (Diester-Hass et al,
2009; Savin et al, 1985). These giant shark genera
included the hexanchiforms (Hexanchus), lamniforms
(Alopias, Carcharocles, Carcharodon, Cosmopolitodus,
Isurus, Parotodus), and carcharhiniforms (Galeocerdo,
Hemipristis). The teeth of these sharks well-known and
present in museum collections with the exception of
those of the both giant thresher sharks, Alopias spp.
A fairly realistic model
of a thresher shark.
A model of a thresher
shark, probably modified
from that of a great white
shark. The elongated tail is
much shorter than that of any
Recent thresher.
Outlines of a Recent and a giant Miocene thresher shark, approximately in
proportion.
ACKNOWLEDGMENTS
This study would not have been possible without the
stratigraphic knowledge and generosity of a number of
amateur fossil collectors, commercial fossil collectors and
fossil dealers from the USA and Europe, including Peter
Pickard, Mark Palatas, after whom the species is named,
Steve Alter and Mark Havenstein. Stratigraphic
information for the Maltese occurrences was supplied by
Charles Bonavia and Arie Janssen.
amateur collectors and fossil dealers but had no mention
in the scientific literature.
Through the generosity of a fossil dealer, a single tooth was
obtained by DJW, on the understanding that it would be
formally described. This, and other teeth examined,
conformed closely to the size and variation seen in Alopias
grandis. The specimen was collected from a river in South
Carolina, so the stratigraphic provenance was uncertain.
During the course of the study it became evident that such
teeth were frequently found in the early/mid Miocene
sediments in Maryland, South Carolina and occasionally on
the island of Malta. A specimen, found in situ at Calvert
Cliffs, Maryland, USA, now in the collections of Calvert
Marine Museum, was chosen to be the holotype.
was that they were a serrated variant of Alopias
grandis. Curiously, these teeth were well known by
Otodus megalodon or Parotodus
benedini, but the general consensus
