Paleontologists have provided new insight into the early changes in the shape of teeth in mammals, providing new insight into the evolutionary history of these ancient animals. The discovery, made by a team of international researchers including Professor Patricia Vickers-Rich from Monash University’s School of Earth, Atmosphere and Environment, was published on: Nature.

The study, conducted by a team of paleontologists from institutions in New York, China and Australia, examines the dental structure of Jurassic Shuteriids to better understand their phylogenetic relationships and evolutionary pathways.

“Our research challenges existing theories and offers a new perspective on the evolutionary history of mammalian forms,” ​​said Professor Vickers-Reach. “We provide vital insight into the phylogenetic relationships and evolutionary trajectories of shuotheriids, little known until recent discoveries in China, by explaining their complex tooth shapes and occlusal patterns,” he said.

Schuotheriids, mammal-like animals of the Jurassic period, surprised scientists with their unique dental features.

Schuotheriids had so-called “pseudotribosphenic teeth”, with a “pseudothalonid” (shell-like structure) located in front of the trigonid on the lower molars, in contrast to the tribosphenic pattern seen in extant Therian mammals, where the talonid is present. behind the trigonid. .

“This unique dental pattern has hindered our understanding of the relationships of scotheriids and the first steps in the evolution of mammalian species,” said Professor Vickers-Rich.

The research team used advanced techniques to uncover new specimens of Jurassic shuotheriids, some with complete skeletons, allowing them to examine their “pseudotribosphene” teeth. In analyzing this new material, researchers were able to analyze tooth structures more comprehensively through various analyses; This revealed that the dental structures of schuteriids were very similar to those of docodontians.

The study shows that shuotheriids lack a true trigonid in their lower teeth, indicating a closer relationship with docodontans than previously thought. This reassessment of dental architecture not only resolves unresolved interpretations but also encourages revision of evolutionary relationships in mammalian forms.

Co-author Dr. from Research Institute Museums Victoria. Thomas Rich said: “In 1982, Minchen Chow and I placed a small four-toothed Jurassic lower jaw at one point in the mammalian family tree. Now, two nearly complete specimens analyzed in a different way place them in a completely different place in the mammalian family tree, and Different methods offer different interpretations.

According to these new data, shuotheriids belong to another class called Docodontiformes, separate from ausctribosphenids, and are therefore united with the docodontan group. This discovery highlights the importance of pseudotribosphene features in explaining the early diversification of mammalian forms.

“The study highlights the existence of significant diversity in tooth morphology in early mammalian forms, indicating unique ecomorphological adaptations throughout the evolutionary development of mammals,” said Professor Vickers-Rich.

“Tooth changes, such as transverse expansion of the posterior teeth, rearrangement and even rotation of the teeth, are indicative of the many ecological niches inhabited by early mammal forms.”