A ‘dinosaur’ fossil known as Bathygnathus borealis has been shown to have steak knife-like teeth, and a team of Canadian paleontologists has changed its scientific name to Dimetrodon borealis.
Dimetrodon borealis is shown with an overlay of the ‘Bathygnathus’ fossil from Prince Edward Island, with a Walchia tree in the background – a common fossil found on the island. Dimetrodon borealis lived about 285 million years ago during the Artinskian stage of Permian. Image credit: Danielle Dufault.
Known from a single specimen, Bathygnathus borealis has a long and intriguing taxonomic history. It is the second vertebrate fossil named from Canada (Dendrepeton acadianum was named a few months earlier) and the first non-mammalian synapsid ever found.
Originally collected on Prince Edward Island, Canada, in 1845, the Bathygnathus specimen was not formally named until 1853, and described in 1854 as the dentary of a bipedal saurian.
“Subsequently, it was erroneously considered a dinosaur until the specimen was recognized as a theriodont in 1876, and later identified as the partial snout of a sphenacodontid,” Prof. Robert Reisz from the University of Toronto and his colleagues wrote in a paper in the Canadian Journal of Earth Sciences.
Using family trees and imaging techniques to see the internal anatomy of the fossil, Prof. Reisz and co-authors found that the eight preserved teeth linked the fossil to the Dimetrodon group – the first terrestrial animal to have ‘ziphodont’ teeth.
“These are blade-like teeth with tiny serrations along the front and back of the teeth, similar to a steak knife,” Prof. Reisz said.
“The roots of these teeth are very long, around double the length of the crowns. This type of tooth is very effective for biting and ripping flesh from prey.”
“Dimetrodon borealis is actually more closely related to mammals than it is to dinosaurs. In fact, it’s believed they went extinct some 40 million years before the dinosaurs,” said team member Dr Kirstin Brink, also of the University of Toronto.
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Kirstin S. Brink et al. 2015. Re-evaluation of the historic Canadian fossil Bathygnathus borealis from the Early Permian of Prince Edward Island. Canadian Journal of Earth Sciences 52 (12): 1109-1120; doi: 10.1139/cjes-2015-0100
