A pycnodont with piranha teeth

[Halichoeres]

Piranhas aren't really that scary unless you step on their nests or otherwise harass them, but one reason they can do damage to larger animals is that their teeth interlock and can cut pieces (contrast to a pike, which has serious teeth but they're all piercing teeth). Pycnodonts, the coral- and algae-eating fishes of the Mesozoic, produced some fishes that work a lot like piranhas. Here's one called Piranhamesodon (from "piranha" obviously, and "Mesodon", another pycnodont genus), which is the earliest known actinopterygian capable of cutting chunks of animals.

The fossil:


The paper (open access): https://www.cell.com/current-biology/fulltext/S0960-9822(18)31208-9

And another paper describing some other predatory pycnodonts last year, including the genus Serrasalmimus ("piranha mimic"): https://www.nature.com/articles/s41598-017-06792-x

And finally, a write-up on CNN with a somewhat goofy illustration: https://www.cnn.com/2018/10/18/world/flesh-eating-fish-fossil-jurassic/index.html

[Gothmog the Baryonyx]

The fossil looks quite interesting. Are there any other pycnodonts like this?

[Halichoeres]

I'm only aware of this one and the three genera described in the Scientific Reports paper in 2017, including Serrasalmimus. The new one is more complete than any of those, though.