New research sheds light on old fossil and solves evolutionary mystery

A new research paper published in Biology letters revealed that picrodontids, an extinct family of placental mammals that lived several million years after the extinction of the dinosaurs, are not primates as previously believed.

The article, co-authored by Jordan Crowell, who holds a Ph.D. in anthropology. candidate at CUNY Graduate Center; Stephen Chester, associate professor of anthropology at Brooklyn College and the Graduate Center; and John Wible, curator of mammals at the Carnegie Museum of Natural History, is important in settling a paleontological debate that had simmered for more than 100 years while helping to paint a clearer picture of primate evolution .

For the past 50 years, paleontologists have believed that picrodontids, which were no larger than a mouse and likely ate foods such as fruit, nectar and pollen, were primates, based on characteristics of their teeth that they share with living primates. But using modern CT scanning technology to analyze the only known preserved picrodontid skull at Brooklyn College’s Laboratory of Evolutionary Mammal Morphology, Crowell, the lead author of the paper, worked with Chester, the lead author of the ‘article, and Wible to determine that they are not closely related. to primates at all.

“While picrodontids share characteristics of their teeth with living primates, the skull bones, particularly the bone surrounding the ear, are unlike those of any living primate or its fossil relatives,” said Crowell. “This suggests that picrodontids and primates independently evolved similarities in their teeth, likely for similar diets. This study also highlights the importance of revisiting ancient specimens with updated techniques for examining them.”

Chester, who holds Crowell’s Ph.D. advisor, has both a professional and personal interest in this research. It was Chester’s famous colleague and “academic grandfather,” Professor Emeritus Frederick Szalay of Hunter College and the Graduate Center at CUNY, who in 1968 first convincingly classified picrodontids as primates, based on evidence from fossilized teeth. Szalay studied the teeth of the only known picrodontid skull, Zanycteris paleocenus, for his research – the same skull that this team examined with the new technology that led to their discovery.

“The skull of Zanycteris was prepared and partially submerged in plaster around 1917, so researchers studying this important specimen at the American Museum of Natural History were unaware of the extent of cranial anatomy hidden over the 100s last few years,” Chester said. “The micro-CT scanner has revolutionized the field of paleontology and allows researchers to discover much more about fossils previously studied and preserved in natural history museum collections.”