Hypercarnivory, Tooth Development, and Evolutionary Dead Ends – #365papers – 2017 – 78

#365papers for March 19, 2017

Sole and Ladeveze, 2017, Evolution of the hypercarnivorous dentition in mammals (Metatheria, Eutheria) and its bearing on the development of tribosphenic molars: Evolution & Development, v. 19, p. 56-68.

What’s it about?

This paper discusses the teeth of carnivorous mammals, in particular the carnassials, or cutting teeth, characteristic of a meat-eating diet. These are the long, bladelike teeth toward the back of a dog or cat’s jaw, that come together with a scissor-like action to snip off bits of meat. Mammals from many different groups (including marsupials) have developed carnassial teeth.

The degree to which these teeth are blade like or still possess some of the crushing and puncturing features of ancestral mammals is an indication of how dependent on meat the mammal is. Cats, for example, lack the crushing and puncturing structures and are thus ‘hypercarnivores.’ Dogs in contrast, still have these ancient structures and are known to have a broader, more flexible diet.

Why does it matter?

First, the authors observe that hypercarnivory appears to be a dead-end adaptation. When a lineage develops hypercarnivory, it can’t go back to a more flexible diet, and is a great risk of extinction because of its specialized diet.

Second, the authors track the appearance and positions of important cusps on the molars of ancestral mammals toward hypercarnivorous mammals. All living mammals share a basic tooth pattern called the tribosphenic molar, which includes a particular set of cusps, grinding basins, and shearing surfaces. The tribosphenic molar evolved from a more primitive tooth with a row of three cusps. It’s possible that the hypercarnivorous carnassial tooth is a reversion to this primitive condition.

Why did I read this?

My doctoral work was on Paleocene mammals, all of which (72 species) I identified based on the arrangement and relative sizes of cusps on the basic tribosphenic molar plan. Carnivores are cool and interesting, so I wanted to read this.

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