Shark-Headed Human Ancestor Swam With Fishes
Peer far enough back in the human family lineage, and you’ll find a fishy ancestor that looked surprisingly like a shark. In fact, this now-extinct fish was among the first to split from sharks, whose bones are made of cartilage, to evolve into a line of tough-boned species that includes everything from bony fish to human beings. A new analysis finds that this controversial class of animals was more shark-like than expected.
The study also revised the relationships between early gnathostomes, or vertebrates with jaws (whose members range from fish and sharks to birds, reptiles and humans), and the most primitive members of that group, armored fish called placoderms. The researchers found distinctive anatomical differences between placoderms and other gnathostomes. All of the updated relationships will allow researchers to look more closely at how fish made the transition from jawless to jawed.