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A new giant of thresher from the of the

Poster · October 2015 DOI: 10.13140/RG.2.1.1723.0969

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David John Ward Natural History Museum, London

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The user has requested enhancement of the downloaded file. A new giant species of 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

MIOCENE SHARK RECENT THRESHER SHARKS In the late Early and Middle Miocene there was burst of gigantism in a number of unrelated species of shark. This Thresher sharks (Alopias spp.) are readily identified by event corresponded with the warmest interval of the their elongated caudal fins, that allow them to both , the "middle Miocene climatic optimum", an swim rapidly and stun prey. interval of high oceanic productivity (Diester-Hass et al, There are three Recent species of thresher with World 2009; Savin et al, 1985). These giant shark genera Wide [WW]or Indo-Pacific [IP] distribution. included the hexanchiforms (Hexanchus), lamniforms (Alopias, Carcharocles, , , Alopias vulpinus WW – surface waters. , ), and carcharhiniforms (Galeocerdo, Alopias pelagicus IP– surface waters. A fairly realistic model Hemipristis). The teeth of these sharks well-known and Alopias superciliosus WW – deep water. of a thresher shark. present in museum collections with the exception of All three Recent species have small, those of the both giant thresher sharks, Alopias spp. fairly homodont dentitions.

Alopias grandis , .

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 Tooth of the holotype of the new giant serrated thresher shark. Formation of Nomini Cliffs, Westmorland County, Virginia. The second, a somewhat larger specimen, was It is unlikely that the new giant reworked from the Neogene of the Charleston area thresher shark possessed an This species, although not particularly rare, has received elongated dorsal tail lobe seen little attention in the subsequent literature. in the Recent species. As the dentition is converging on a A GIANT SERRATED - TOOTHED ALOPIAS and its size Left lower jaw, of Alopias vulpinus, lingual view, showing incipient lateral cusplets. In around 2002. rumours were circulating about was similar or larger, it is another large species of lamniform shark reasonable to suppose that the body outline was similar. THRESHER SHARKS with serrated teeth from the Miocene The oldest known fossil teeth of Alopias are from the early of South Carolina. Some teeth The plastic model (left) : Alopias crochardi Ward 1978, from the London were dismissed as possibly supposedly of a thresher but Clay and Alopias denticulatus Cappetta 1981, from the being upper laterals with a much shortened tail, by Moroccan phosphates. The latter has small lateral cusps, a of one of the chance, corresponds to this feature still present in juvenile teeth of Alopias vulpinus. known giant body outline. sharks ; 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.

Outlines of a Recent and a giant Miocene thresher shark, approximately in proportion.

A model of a thresher ACKNOWLEDGMENTS shark, probably modified This study would not have been possible without the from that of a great white stratigraphic knowledge and generosity of a number of shark. The elongated tail is much shorter than that of any amateur fossil collectors, commercial fossil collectors and Recent thresher. fossil dealers from the USA and , including Peter Pickard, Mark Palatas, after whom the species is named, Teeth of Alopias spp., from the late Eocene of Kazakhstan. Steve Alter and Mark Havenstein. Stratigraphic or Parotodus information for the Maltese occurrences was supplied by benedini, but the general consensus Charles Bonavia and Arie Janssen. was that they were a serrated variant of Alopias grandis. Curiously, these teeth were well known by REFERENCES amateur collectors and fossil dealers but had no mention DIESTER-HAASS, L., K. BILLUPS, D. R. GROCKE, in the scientific literature. L. FRANCOIS, V. LEFEBVRE, &K. C. EMEIS. 2009. Mid-Miocene paleoproductivity in the Atlantic Ocean and Through the generosity of a fossil dealer, a single tooth was implications for the global carbon cycle, obtained by DJW, on the understanding that it would be Paleoceanography, 24: 1209. formally described. This, and other teeth examined, conformed closely to the size and variation seen in Alopias SAVIN, S. M., ABEL L., BARRERA, E., HODELL, D., grandis. The specimen was collected from a river in South KELLER, G., KENNETT, J. P., KILLINGLEY, J., Carolina, so the stratigraphic provenance was uncertain. MURPHY, J. M. &VINCENT, E. 1985. The evolution of Miocene surface and near-surface marine temperatures: During the course of the study it became evident that such oxygen isotopic evidence, GSA Memoir, 163: 49-102 teeth were frequently found in the early/mid Miocene sediments in Maryland, South Carolina and occasionally on KENT, B. W. & WARD, D. J. in press. Addendum: A the island of Malta. A specimen, found in situ at Calvert new species of Miocene giant thresher shark (Alopias) Cliffs, Maryland, USA, now in the collections of Calvert with serrated teeth. In: S. Godfrey (ed.), The geology and Marine Museum, was chosen to be the holotype. vertebrate of Calvert Cliffs (Chesapeake Group), Maryland, USA. Smithsonian Contributions to Paleobiology. Bretton W. Kent [[email protected]] David J. Ward [[email protected]]

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