Dental examination of fossils more than 200 million years ago showed that the earliest true teeth were composed of monster species called Gemini teeth.
The evidence, published today in the proceedings of the Royal Society B, may help clarify how species from elephants and walruses to pigs and rabbit hyenas grow ivory.
“Ivory has evolved many times, which makes you wonder why? Why?” study co-author Christina? SIDOR is a professor of biology at the University of Washington and curator of the UW Burke Museum of natural history and culture, he said at a news conference. “We now have good data on the anatomical changes required by dicotyledons to evolve ivory. As for other groups, such as warthogs or walruses, there is no final conclusion.”
Bitodontosaurus existed in the Permian and Triassic period from 270 million to 201 million years ago. It seems to be the earliest animal group with ivory. Their label comes from the Greek meaning “two canine teeth”. Different kinds of canine teeth are between the size of today’s mice and elephants. They are classified as mammalian reptiles or reptilian mammals.
In any case, they are considered to be the ancestors of modern mammals. Megan Whitney, the lead author of the study, who received a doctorate, said: “before I started this research, I never really thought about how Ivory was limited to mammals.”. He is now a postdoctoral fellow at Harvard University.
To explore the origin of ivory, Whitney, SIDOR and colleagues at the field museum in Chicago and Idaho State University analyzed 19 tooth fossil samples representing 10 different bidentate species. Most specimens were collected during expeditions to Tanzania and Zambia. These specimens are currently kept in museums in the United States, but they will return to Africa at the end of the research project.
One of the initial research tasks was to determine the actual composition of ivory. “It’s a surprisingly ambiguous term,” Whitney said.
She and her colleagues believe that to become ivory, teeth must extend out of the mouth and grow continuously throughout the life of animals. Unlike most mammalian teeth, the surface of ivory should be soft dentin rather than hard enamel. For example, this requirement would exclude mouse teeth, even if they sometimes protrude.
Some of the teeth found in the odontosaurus samples also do not qualify as ivory because they are coated with enamel rather than dentin. The researchers scanned the teeth with CT and placed paper samples under the microscope to distinguish long teeth from non long teeth, understand how the teeth attached to the skull and how the teeth grew.
Early dinodontosaurus species tended to have large teeth rather than real long teeth, but these samples showed that over time, multiple species evolved independently to have long teeth. The researchers also found that the ligament attachment between the tooth and the jaw adapted to long teeth over time.
The researchers noted that enamel coated teeth were harder than dentin coated ivory, but teeth were easier to repair after being knocked. “Enamel coated teeth and dentin coated ivory are different evolutionary strategies,” Whitney said. “This is a trade-off.”
Toothed animals are good for rooting on the ground. If they damage the ivory in the fight with the attacker, the damage will eventually be repaired. On the contrary, enamel coated teeth will break permanently.
Future research could shed more light on how tusks were used – and, more broadly, how they lived – by dinodactyls and other ancient species.
“Bones and teeth can record animal life in tissue,” SIDOR said. “On growing long teeth, dentin records daily measurements of the growth rate of animals. Does it grow fast or slow in a specific season? Stops growing at a specific time? Creating thin sheets of bones and teeth opens up many other interesting things about animals, almost like analyzing tree rings. These are some of the questions he raised that we can continue to study.”