by Sarah Boessenecker (@tetrameryx) and Robert Boessenecker (@CoastalPaleo)
Happy Fossil Friday!
Did you know that walruses used to live in the Southeastern US? From about 4 million years ago to as recently as 300,000 years ago these tusked behemoths were inhabiting in the southern most regions of the North Atlantic – as far south as Florida!
A tusk in the hand is worth 2 in the bush? Photo by R. Boessenecker.
Our Friday Fossil Feature today is a partial tusk from Ontocetus emmonsi, a rare Pliocene walrus found in deposits from the Lee Creek Mine in Aurora, North Carolina, recently donated to CCNHM by the estate of Rita McDaniel. Two more tusks are also present in our collection, and are from South Carolina.
Our newest acquisiton, from Lee Creek, at top; female tusk in middle, and male tusk at bottom, both from South Carolina. Photo by S. Boessenecker.
Ontocetus has a long history; it was first described in 1859 by Joseph Leidy, based off of a partial tusk from the Yorktown Formation, collected by Ebenezer Emmons, and is now in the collections at the Smithsonian Museum of Natural History (USNM). Emmons was a professor at Williams College in Massachusetts, and also the State Geologist of North Carolina from 1851-1863, and was honored with Ontocetus being named after him. Many other species of Plio-Pleistocene walruses from the North Atlantic were subsequently proposed, including: Alachtherium cretsii, Alachtherium antwerpiensis, Trichecodon huxleyi, Trichecodon/Odobenus antverpiensis, and Prorosmarus alleni.
The holotype specimen of Ontocetus emmonsi, from USNM. Photo by R. Boessenecker.
A juvenile maxila and tusk, at USNM. Photo by R. Boessenecker.
A monograph published by Naoki Kohno and Clayton Ray (2008) in the Lee Creek Volume IV through the Virginia Museum of Natural History examined and reconsidered specimens of Ontocetus and other walrus material from Atlantic Pliocene deposits. They realized that many species that had been described and presenting problems for scientists were in fact the same species. Rules of zoological nomenclature dictate that if multiple names (synonyms) have been proposed for a single species, the oldest (and thus first proposed) name for a particular species is the correct one. In this case, Ontocetus emmonsi was the first name proposed for the extinct walrus from the Pliocene of the North Atlantic.
Through the simple act of recognizing that all these problematic species represented the same walrus, much confusion was resolved and the range and number of specimens was significantly improved. The larger sample now available from the Pliocene sediments along the North Atlantic margin (Florida, South Carolina, North Carolina, United Kingdom, Netherlands, Belgium, and Morocco) now indicates that Ontocetus was widely distributed down to subtropical latitudes, had shorter and more highly curved tusks than modern walrus, had a more elongate skull, and may have been slightly larger. This walrus had far more of a presence than previously thought in the Pliocene!
Further Reading:
J. Leidy. 1859. [Remarks on Dromatherium sylvestre and Ontocetus emmonsi]. Proceedings of the Academy of Natural Sciences of Philadelphia 1859:162
D. P. B. Erdbrink and P. J. H. Van Bree. 1986. Fossil cranial walrus material from the North Sea and estuary of the Schelde (Mammalia, Carnivora). Beaufortia 49(1):1-9
C. R. Harington. 1984. Quaternary marine and land mammals and their paleoenvironmental implications – examples from Northern North America. Special publication of the Carnegie Museum of Natural History 8:511-525.
N. Kohno and C. E. Ray. 2008. Pliocene walruses from the Yorktown Formation of Virginia and North Carolina, and a systematic revision of the North Atlantic Pliocene walruses. Virginia Museum of Natural History Special Publication 14:39-80
K. Post. 2004. What’s in a name: Alachtherium cretsii, de Pliocene van de Nordzee. Grundboor & Hammer 58:70-74.
L. Rutten. 1907. On fossil trichechids from Zeeland and Belgium. Proceedings of the Royal Netherlands Academy of Arts and Sciences 10(1):2-14
A.E. Sanders. 2002. Additions to the Pleistocene mammal faunas of South Carolina, North Carolina, and Georgia. Transactions of the American Philosophical Society 92:1-152.
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