Researchers find surprising connection between prehistoric dinosaurs and mammals in their teeth


Thin section of a partial Gorgonopsian canine under polarized light. The conditions are clear on the right side of this sample. Sincerely: Megan Whitney

When most people think of cruel, blade-like teeth on prehistoric creatures, they draw Smilodon, Better known as the saber-toothed tiger. But in the world of dinosaurs, theropods are well known to have blade-like teeth and are used to cut cutting edges. And until recently, the complex arrangement of tissues that gave rise to these terrible teeth was considered unique to these meat-eating dinosaurs.

16 December in a letter published in Biology letter, Lead author Megan Whitney, a postdoctoral fellow in the Department of Organism and Evolutionary Biology, Harvard University, examined thin fossil slices of Gorgonopsian teeth and discovered a similarly complex arrangement of tissues that led to steak-nif-like serrations in theropods. .

Gorgonopsian is a group of synopsids from the mid-late Permian to 270–252 million years ago. Like other synonyms, these animals are considered precursors of mammals and fall within the lineage that eventually give rise to mammals. “These animals were the top predators of their day and were characterized by saber-like canine that could grow up to 13 cm long,” Whitney said.

Previous studies of theropod dinosaurs revealed a complex arrangement of tissues composed of both enamel and dentine that formed cracks for their teeth. This complex arrangement was considered unique for the treatment of dinosaurs. But no one had previously made a thin section of a Gorgonopsian tooth to examine the teeth of whites.

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An entire saber-toothed canine from a Gorgenopsian of Zambia. This specimen includes both the crown of the tooth (above) and the root (below). Sincerely: Megan Whitney

Inspired, Whitney and co-authors combined their expertise in paleohistology (studying the microstructure of fossil skeletal tissue) and fossils from three synapsids from three different time periods to test the theory of the structure of sequences in this group. Examined thin sections of. . “We were surprised to see theropod-like disturbances in the gorgonopsians,” Whitney said. “We wanted to see how other carnivorous synapsids made their divisions, so we saw an old analogy [Dimetrodon] And a small, mammalian synonym [Smilodon]. “

Gorgonopsian, Dimetrodon, And Smilodon All are synapsids and as theropods were the top predators of their day and were serrated, knife-like teeth (ie zipodonti). Dimetrodon Is one of the oldest synonyms during the Sisuarian era, dating from about 295 to 2 years2 million years ago; Dimetrodon Often mistakenly described as a dinosaur. Smilodon Lived in the Americas 10,000 years ago during the Pleistocene Era 250 million years ago. “All these animals come with a mammal line that is different from the reptile line with dinosaurs,” Whitney. “In fact, these three animals are more closely related to humans than dinosaurs.”

Whitney’s Ph.D. The focus was on the teeth of mammals’ gorgonopsians and other precursors, so they examined Gorgonopsian specimens that were collected from extensive fieldwork in Zambia, where many of these animals are found. Co-authors Aaron LeBlanc, Postdoctoral Fellow in the Department of Biological Sciences, University of Alberta, Ashley Reynolds, Ph.D. Candidate at the Department of Ecology and Evolutionary Biology, University of Toronto and Kirsten Brink, Assistant Professor at the Department of Geological Sciences, University of Manitoba, contributed expertise in dentistry and animals involved in this study.

Thin sections showed that Gorgonopsian serials were made up of tightly filled serrations made of both enamel and dentine, the same complex arrangement of tissues previously thought to be dinoporous and considered unique. “What’s surprising is that like meat-eating dinosaurs of the Mesozoic era, Gorgonopian has more serian types”, LeBlanc said. “This means that this type of bite tooth first evolved as a lineage for mammals, only later evolved independently into dinosaurs.”

What sharp teeth do i have

Both are magnified images of segments under polarized light. Gorgonopsian serrations are composed of both enamel (thin, light tissue on the right) and dentin (thick tissue on the left) and an interdental fold (the black central structure that is a fold between the serres). This special arrangement allows the teeth to be more tightly packed to fit in and make each series more resistant to wear. Sincerely: Megan Whitney

“The fact is that we only develop this type of seriation in meat-eating animals,” Brink said. “The small microstructures hidden inside the teeth provide a significant benefit to the teeth, which tighten the teeth and help them last longer in the mouth, helping the animal to eat efficiently.”

Although the Gorgopians share this trait with theropod dinosaurs, they actually share more characteristics with other commonalities Dimetrodon And humans. “These animals transitioned to serology morphology of similar teeth because of functional benefits, not because they are close relatives to each other,” Whitney said. “In this case, it probably has something to do with the fact that the animals actually wear and tear too much on their teeth. And so independently they have been able to form a serration that replicates forces of repetition. Is going to cope. It is important to eat to eat. Therefore, there is a lot of selection on the teeth. “

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Gorgonopsian was the first saber-toothed animal. His canine increased to 13 cm. Credit: CCA 3.0 / Dmitry Dogdanov

The Gorgonopsians were a diverse group with body sizes ranging from a medium-sized dog shape to Bear and Whitney’s notes, although the specimens had this type of morphology, it is possible that there was a diversity of serius types that Do you match? Variety of Gorgonopsian.


Fossil evidence of tumors in the 255 million-year-old mammal precursor


more information:
Incorporated dental adaptation into hypercarnivorous synapse and dinosaur sequences. Biology letter, royalsocietypublishing.org/doi… .1098 / rsbl.2020.0750

Provided by Harvard University

Quotes: Researchers Detect Surprising Relationship Between Prehistoric Dinosaurs and Mammals in Their Teeth (2020, 15 December) from https://phys.org/news/2020-12-prehistoric-dinosaurs-mammals-teeth.html 16 December 2020 Was retrieved.

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