6. Something wondrous
A 130-million-year-old skull discovered in Utah is a rare fossil find that suggests primitive relatives of today's mammals lived throughout the supercontinent of Pangea, according to research published Wednesday in Nature.
What they found: Researchers unearthed a small, largely intact skull — about 7 cm long — from a new species, Cifelliodon wahkarmoosuch, that is part of a now extinct group of animals called the haramiyids. Their place on the tree of life is debated. Some scientists consider them members of the mammal family, while others view them as near relatives that share a common ancestor. Going with the former means mammals emerged 215 million years ago, the latter 30 million years later.
- C. wahkarmoosuch's highly specialized teeth and roots, primitive palate and about two-dozen other features indicate it is very closely related to mammals, but just outside the family, says Zhe-Xi Luo, a paleontologist at the University of Chicago and an author of the study.
- The complete skull is important for haramiyids as a whole because "it shows for the first time what the brain structure was like," says Luo.
Key insight: The teeth of C. wahkarmoosuch are very similar to ones in a haramiyid fossil found in Morocco. The authors argue those similarities geographically link North America and North Africa — contradicting the prevailing thought that Pangea was completely broken up by that time.
"Tying this to the breakup of Pangea is an interesting idea but cannot be proven at this point. There are other potential options but this is viable option,” says the University of Louisville's Guillermo Rougier, who was not involved in the research.
For Rougier, the skull highlights how little the southern continents are represented in the fossil record. “Most of what we know from early mammals comes from North America, Europe and Asia. We still have about half of the picture missing.”