The oldest evidence of a creature with tusks dates back more than 200 million years ago before the dinosaurs roamed the Earth.
The earliest known tusks were found on animals called dicynodonts that were around prior to modern mammals between 270 and 201 million years ago. They could be as small as a rat or as large as an elephant. Their most interesting feature was their protruding tusks in the upper part of their jaws that curved downwards from the canine area. While they’re not considered mammals, they are their distant relatives.
A team of researchers came up with the idea to study ancient tusks during a paleontological dig as explained by Megan Whitney who is a postdoctoral fellow in the Department of Organismic and Evolutionary Biology, Harvard University, “We were sitting in the field in Zambia, and there were dicynodont teeth everywhere.” “I remember Ken picking them up and asking how come they were called tusks, because they had features that tusks don’t have.”
The researchers analyzed fossil tissue on ancient teeth belonging to 19 fossils that came from 10 different dicynodont species. Specifically, they studied how the teeth were connected to the skull and looked at the possibility that they continued to grow throughout the creature’s life.
Several tusk specimens had enamel coatings instead of dentine which was rather odd as Whitney explained in further detail, “There are many different kinds of dicynodonts and they appear to mostly all have tusks.” “However, when you look at the micro structural details they’re very different in those groups.” Enamel makes teeth much stronger than dentine but they wouldn’t be able to grow back if one was lost. Additionally, they had a soft tissue attachment to their jaw.
“If you have these two things, a reduced amount of tooth replacement and a soft-tissue attachment, an ever-growing tooth allows the animal to get around the fact that it cannot replace the tooth. Instead it evolves to continuously deposit the same tooth tissues,” Whitney stated. “And as the animal continues to deposit the tissue, the tooth begins to move outside of the mouth to become functional.” While it’s unclear what the dicynodonts used their tusks for, they could have been for burrowing, competition, defense, moving around, and sexual selection.
Another interesting fact is that dicynodonts only evolved their tusks in the late stages of their evolution as the earlier species had large teeth instead. “Dicynodonts were the most abundant and diverse vertebrates on land just before dinosaur times, and they’re famous for their ‘tusks.’ The fact that in reality only a few have true tusks, and the rest have big teeth, is a beautiful example of evolution we can document,” noted Brandon Peecook who is a curator at the Idaho Museum of Natural History. The study was published in the Proceedings of the Royal Society B.
A picture of a dicynodont skull with a tusk and an image of what the creature would have looked like can be seen here.