Carboniferous shark fed like a teleost

[Halichoeres]

Suction feeding is widespread in teleost fishes (from goldfishes to tunas). The trunk muscles pull on the back of the head, as well as on the gill cover and lower jaw, rapidly opening the jaws and allowing the sudden pressure difference to transport food into the mouth. It's a really efficient way to eat something that's a short distance away. Modern sharks, by contrast, usually must bite their prey. The Carboniferous stem-shark Tristychius arcuatus, in a new study, shows evidence of having fed by suction, millions of years before actinopterygian fish acquired the same ability. This figure shows the cycle of motions of each of the several mobile jaw elements, as well as the change in volume of the mouth, creating the necessary pressure differential.


If you click through to the supplement there are some cool animations of the jaw working.

An illustration by Kristen Tietjen, one of the study's authors:


Open access in Science Advances: https://advances.sciencemag.org/content/5/9/eaax2742

And a nice write-up from the University of Chicago press office: https://www.sciencedaily.com/releases/2019/09/190911142835.htm

[ZoPteryx]

That's really cool!  So how is this different from what modern carpet sharks do?

[Ravonium]

That's really cool!  So how is this different from what modern carpet sharks do?

I would like to know this as well (although regardless of the answer, this is still a pretty cool discovery  )

[Halichoeres]

It's really quite similar to a carpet shark, which the paper points out. They also CT scanned a brownbanded bamboo shark, and the only difference they find worthy of mention is the larger retroarticular process of the Meckel's cartilage in Tristychius. The reason this is a big deal isn't that it's a completely novel morphology, it's that it happened in the Carboniferous (carpet sharks don't appear until the Jurassic). It also means that this kind of feeding evolved in sharks first, rather than in bony fishes as previously supposed (but both are independent of each other, of course).