Dimetrodon is Greek for “two measures of teeth.” Many are prone to the mistake of calling it a dinosaur, but this ancient creature was actually a reptile. By some estimates, Dimetrodon lived almost 300 million years ago in North American swampland, some 50 million years before the first dinosaur. It existed at the top of its food chain in the early Permian Period.
In a new study in Nature Communications, Kirstin Brink and Robert Reisz, both from the University of Toronto Mississagua, laud Dimetrodon as one of the first Earth-walking vertebrates to have more than one tooth shape, a large skull, and compressed, recurved teeth with a distinct type of cutting edge. It appears to also have been the first animal to have bitten through flesh with serrated teeth.
According to Brink and Reisz, Dimetrodon’s tooth morphology is characterized by smooth edges for cutting as well as pointed ends and pointed projections.
These ancient reptiles exhibited three types of teeth, each characterized by a different species within the genus Dimetrodon. Dimetrodon grandis, the most recent species, had teeth specifically for cutting. Dimetrodon limbatus, more ancient, had small saw-like teeth. Lastly, the earliest Dimetrodon milleri had straight teeth with cutting edges. The change in tooth morphology, hypothesized the authors, were caused by an ongoing battle between Dimetrodon and sphenacodontids, contemporaries of Dimetrodon that had very similar skull anatomy and fed on the same prey. Additionally, the teeth of the D. grandis may have developed to increase the viability of certain animals for prey. Evidence also suggests that the Dimetrodon grew in size as its prey did.
The skull of Dimetrodon with a close-up of a section of the tooth serrations.
Dental morphology changes in this organism can occur without changes in the shape of its skull; this suggests that differences in tooth shape have to do with differences in eating habits and other intra-species interactions within its environment rather than varying morphology of the skull itself. Furthermore, the researchers note that recurved and serrated teeth first evolved in Dimetrodon independent of similar teeth found in a few ancestors of mammals.
Brink and Reisz point out that more data is needed to discover the true association between competition, size, and tooth shape. For now, we can be satisfied with newfound knowledge of dental diversity.
Source: Brink, K. S., & Reisz, R. R. (2014). Hidden dental diversity in the oldest terrestrial apex predator Dimetrodon. Nature Communications, 5. doi: 10.1038/ncomms4269
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