Canada has its First Dimetrodon

Canada’s First Dimetrodon

A fossil found by a farmer digging a well on Prince Edward Island over 160 years ago has been finally identified by a student whilst studying for a PhD at the University of Toronto Mississauga.  The fossil, which consists of elements of the snout and upper jaw was once thought to have come from a meat-eating dinosaur, but a new analysis reveals that fearsome Dimetrodons once roamed Canada.  This is the first evidence that these giant, sail-backed reptiles from the Permian lived on the landmass that was to eventually form Canada.

Evidence of Dimetrodon in Canada

The curved teeth in the upper jaw can be clearly made out.

The curved teeth in the upper jaw can be clearly made out.

Picture Credit: (Carleton University/University of Toronto Mississauga)

The location of the fossil find remains a mystery, there may be more elements of this individual preserved, but the farmer did not provide a map of the location and what notes that have been attributed to this specimen make no mention of the actual spot where the discovery was made.  All we know is that the well was being dug near the French River (Prince Edward Island).  The specimen was acquired by the Academy of Natural Sciences (Philadelphia, USA) and Joseph Leidy, one of the world’s most eminent palaeontologists, studied it and named it Bathygnathus borealis.  Leidy thought that the fossilised bones and teeth (fragments of the premaxilla, a partial maxilla and elements of the naris along with several teeth), resembled those of Theropod dinosaurs that had been found in England.  Professor Leidy had incorrectly identified this fossil material as a dinosaur, making it the first dinosaur known from Canada.

A review of the fossil in 1905, identified it as a probable mammal-like reptile, however, it was a paper published in the academic journal “The Canadian Journal of Earth Sciences”, late last year that finally cleared up the mystery identifying the animal as a member of the Dimetrodon genera.

Lead author of the paper, Kirstin Brink who worked on the fossil whilst at the University of Toronto Mississauga, and a specialist in examining the teeth of prehistoric animals, explained:

“It’s really exciting to discover that the detailed anatomy of the teeth has finally allowed us to identify precisely this important Canadian fossil.”

An Illustration of the Canadian Dimetrodon

An illustration of Dimetrodon borealis, the insert shows the location of the fossil on the animal.

An illustration of Dimetrodon borealis, the insert shows the location of the fossil on the animal.

Picture Credit: Danielle Dufault

Dimetrodon – A New Species

Dimetrodon is perhaps one of the most famous of all the animals known from the Palaeozoic Era.  Several species of these sail-backed reptiles are known and their fossils have been found in the United States, Europe and now Canada.  The largest species, animals like D. grandis were the apex predators of terrestrial environments during the Late Permian, with some animals growing to around 3.5 metres in length.  Although not a dinosaur, Dimetrodon seems to have become forever linked with the Dinosauria.  For example, Dimetrodon models are often included in dinosaur model sets.

A Dimetrodon Model

Sail-back reptile with ferocious teeth.

Sail-back reptile with ferocious teeth.

Picture Credit: Everything Dinosaur

Kirstin has specialised in studying the preserved teeth of prehistoric animals.  Using parsimonious relationship analysis (family trees) and high resolution imaging, the researchers were able to link the teeth to the Dimetrodon genus.  The teeth are “ziphodont”, that is, they are serrated along the cutting edge.  Dimetrodon is thought to be the first terrestrial vertebrate to possess such teeth.

Professor Robert Reisz (University of Toronto Mississauga), one of the author’s of the research paper published last year stated:

“These are blade-like teeth with tiny serrations along the front and back of the teeth, similar to a steak knife.  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.”

What’s in a Name?

Long tooth roots and these ziphodont serrations are diagnostic of Dimetrodon, ironically, the renaming of this animal from Bathygnathus borealis to Dimetrodon borealis might spell trouble for all fans of this sail-backed reptile.  As Bathygnathus was named before the Dimetrodon genus was erected, then technically, under the strict guidelines of the International Code of Zoological Nomenclature (ICZN) the name given first should take precedence.

In essence, all fossil material related to the Dimetrodon genus should be renamed as Bathygnathus (the name means “deep jaw from the north”).

Dr. Brink, now based at the University of British Columbia expressed her concern:

“What we’re hoping will happen is the priority will be reversed so we can keep Dimetrodon as a valid name, just because it’s so well known among the public and other scientists as well.”

Although the fossil material has not turned out to be a dinosaur, the naming of a new species of Dimetrodon, one that lived further north than any other species of Dimetrodon so far described, still makes this specimen a very remarkable fossil indeed.

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