Its lower fangs slid into holes in its upper jaw.
It's a fish called Brazilichthys. Without those holes, it couldn't shut its jaws all the way.
About two hundred and eighty million years ago, it hunted in the rivers and lakes of what is now Brazil.
All we have is one skull, about as long as your finger.
Scientists scanned it with X-rays and rebuilt the jaws on a computer.
Each jaw had three lines of teeth, and the biggest were curved fangs.
When it bit down, the lower fangs slid into a line of holes on the inside of the upper jaw.
The front fangs were smaller, so the front of the jaw has no holes.
Were the holes just sockets for new teeth? The scientists say no. Those sockets sit between the upper fangs, and the holes don't line up with the upper teeth.
A few living fish, like gars, have a hole or two near the tip of the snout. Brazilichthys had a long line of them.
So those big fangs were never in the way. Its upper jaw made room for them.
