If you went back to visit your earliest known primate ancestors, you’d find them in the trees. New fossil evidence shows Purgatorius, a small, squirrel-like insect and fruit-eating mammal, was a tree-dweller.
Paleontologists analyzed 65 million-year-old fossil ankle bones found in Northeastern Montana to clear up questions about the habitat of Purgatorius, which started kicking around shortly after non-avian dinosaurs went extinct.
“The textbook that I am currently using in my biological anthropology courses still has an illustration of Purgatorius walking on the ground. Hopefully this study will change what students are learning about earliest primate evolution and will place Purgatorius in the trees where it rightfully belongs,” said Stephen Chester, the paper’s lead author, an assistant professor at Brooklyn College, City University of New York.
Before the ankle bones were found in Montana, scientists only had the creature’s teeth and jaws to work with. But the structure of the bones makes it clear that Purgatorius headed for the trees.
“The ankle bones have diagnostic features for mobility that are only present in those of primates and their close relatives today,” Chester said. “These unique features would have allowed an animal such as Purgatorius to rotate and adjust its feet accordingly to grab branches while moving through trees. In contrast, ground-dwelling mammals lack these features and are better suited for propelling themselves forward in a more restricted, fore-and-aft motion.”
The research supports the idea that primates split from other mammals gradually, as they changed to get around the trees better and more efficiently gather food in their arboreal habitats.
[Source: Yale University]
Image by Patrick Lynch