Myological variability in a decoupled skeletal system: Batoid cranial anatomy

What is it about?

Fishes have their jaws unattached directly to the skull, unlike our jaws. In the cartilaginous fishes (sharks and rays) - the connection between the jaws and skull is even more detached - allowing these fishes the incredible ability to protrude their jaws away from their face during feeding. We document which muscles stingrays use to support their jaw skeletal system, as stingrays have the most detached system of all!

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Why is it important?

We found a trend throughout sharks, rays, and their relatives ratfishes that the greater separation between the jaws and the skull, the greater the diversity in muscle anatomy. Stingrays, with the most detached jaws, have more muscles and more complex muscle arrangements than sharks or ratfishes. This fundamental difference between these enigmatic fishes suggests that the evolution of greater jaw protrusion in stingrays has also drastically changed their anatomy: jaws in stingrays have only a single connection to the skull - muscles provide a large amount of the support for the jaws.