Cephalaspis could grow to about one foot long, about the size of a trout. The headshield probably would have slowed Cephalaspis down, because carrying around a heavy shield would be hard to do, even in water, especially for a small fish. Cephalaspis certainly wasn't very fast, so it probably would have relied on the tough head shield for defense.
|©Copyright 2008 by Mike Viney|
Cephalaspis had two fins right behind the headshield, and also a long, powerful tail with what looks to me like muscle bands, similar to those on a lancelet. They were probably bottom dwellers, hiding among rocks and debris like modern catfish, sturgeon, and stingrays.
Most fossils of armored fish only preserve the bony headshield, but in the case of Cephalaspis many fossils also reveal the tail.
Cephaslaspis was a jawless fish, so it probably had to eat very small prey. But with its bony headshield, it still could have been a formidable hunter of these tiny creatures. It could easily dig up these tiny burrowers with its head and then suck them in quickly, like a modern angel shark.
Cephalaspis probably had a similar lifestyle to Bothriolepis, a bizarre placoderm from the late Devonian.