2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 221-12
Presentation Time: 9:00 AM-6:30 PM


MANN, Arjan, Earth sciences, University of Toronto, 22 Russel street., Toronto, ON M5S 3B1, Canada, RUDKIN, David M., Department of Natural History (Paleobiology), Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 2C6, Canada, EVANS, David C., Department of Natural History, Royal Ontario Museum, 100 Queens' Park, Toronto, ON M5S2C6, Canada; Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street., Toronto, ON M5S 3B2, Canada and LAFLAMME, Marc, Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada, arjan.mann@utoronto.ca

Middle Devonian strata of southwestern Ontario, Canada, have yielded a surprisingly diverse, albeit rare, assemblage of vertebrate fossils. The Dundee Formation on Pelee Island in Lake Erie, Ontario, spans the Eifelian-Givetian boundary (390-387 Ma) and has produced significant amounts of placoderm and sarcopterygians fossil material, most of which is undescribed until now. Here we report two well-preserved sarcopterygian (Onychodontidae) lower jaws, including the new species Onychodus sarcovenator n.sp.. The large (27.8cm), nearly complete right jaw includes nearly complete dentition with 50 tooth positions on the dentary, in addition to at least two poorly preserved prominent symphysial tusks. The anteriormost teeth in the dentary are incomplete, but the second tooth is notably procurved. The posterior teeth are conical and of similar size for much of the length of the tooth row. Infradentary one and four are present, but the gular, submandibular, and infradentaries two and three are not preserved.

Onychodus sarcovenator’s jaw differs from O. sigmoides in that it has a strong dorsally curved anterior dentary ramus, and a strong anterior expansion of the dentary. O. sarcovenator also differs from O. jandemarrai (and others) in its large size and elongated posterior fourth infradentary. An expanded phylogenetic analysis of Devonian onychodontiformes that includes 9 well-known taxa and 41 morphological characters was performed. Parsimony results suggest that O. sarcovenator is sister to O. jandemarrai, supported by (1) shared presence of a mesial ridge running through the entire dentary, (2) the presence of more than 3 coronoids, (3) ribbed enamel on the parasymphysial teeth, (4) ornamented- tuberculated coronoids, as well as (5) the presence of procurved teeth on the anterior end of the dentary.