A '325-million-year-old shark-like species' could help researchers gain insight into jaw evolution.
The research suggests sharks are more evolutionarily advanced than was previously believed, an American Museum of Natural History news release reported.
"Sharks are traditionally thought to be one of the most primitive surviving jawed vertebrates. And most textbooks in schools today say that the internal jaw structures of modern sharks should look very similar to those in primitive shark-like fishes," Alan Pradel, a postdoctoral researcher at the Museum and the lead author of the study, said in the news release. "But we've found that's not the case. The modern shark condition is very specialized, very derived, and not primitive."
Sharks have jaws along with a set of "arches" that support the jaw and gills; these arches are believed to have been how jaws started out millions of years ago.
Sharks have extremely delicate bones, and looking at full species structures from long ago has proved difficult. The Ozarcus mapesae was preserved in a "three-dimensional state," giving researchers a rare glimpse into the past.
"This beautiful fossil offers one of the first complete looks at all of the gill arches and associated structures in an early shark. There are other shark fossils like this in existence, but this is the oldest one in which you can see everything," John Maisey, a curator in the Museum's Division of Paleontology and one of the authors on the study, said in the news release. "There's enough depth in this fossil to allow us to scan it and digitally dissect out the cartilage skeleton."
We discovered that the arrangement of the arches is not like anything you'd see in a modern shark or shark-like fish," Pradel said. "Instead, the arrangement is fundamentally the same as bony fishes."
