Scientists say new studies of fossilized jaw bones show that mammals began to evolve millions of years earlier than was previously thought
University of Chicago palaeontologist Zhe-Xi Luo co-authored the study. Zhe-Xi told Popular Science that the mammalian jaw hinge is unique because the tooth-bearing dentary bone is directly connected to the jaw hinge.
This enables mammals o create more force from chewing and biting than other vertebrates with jaws.
Modern mammals evolved from within a group of animals called Cynodonts. These had a jaw joint consisting of two separate bones – the quadrate of the skull and the articular in the lower jaw and the quadrate in the skull.
Paleontologists previously believed that all mammal sister groups has similar characteristics, but the fossils hadn’t been reexamined using micro-computed-tomography (CT) scans.
Now, in the new study published in nature, the scientists used these techniques to examine 225-million-year-old fossils of two extinct cynodont species from present-day Brazil.
