Placoderm
by Kevin K.
Millions of years ago, a ferocious beast hunted in the ocean water. That beast is a placoderm. The placoderm is a huge fish ranging from 15 to 25 feet. It is an armored fish because of the armor covering the upper torso of this animal. It was the first jawed fish. The placoderm was the most active predator in the marine and fresh waters. Anything it could fit in its mouth, it would eat. Some types of placoderm, would even eat another placoderm.
The two traits that the placoderm evolved were the vertebrate trait and the gnathostome trait. The vertebrate trait means that the placoderm had a backbone and a skull. The gnathostome trait means that the placoderm had a jaw. Those two are very important because they helped the body evolve. The name placoderm means tablet + skin in Greek. The jaw enabled them to bite rather harder food, so they didn’t have to suck up their food.
The closest relative to the placoderm is every animal on the cladogram other than the ostracoderm. I know this because if you follow the line from the placoderm and get to the gnathostome node, which is the most advanced node, and then see what branches come off of that node, you will see that every single animal other than the ostracoderm branches off of the node. That is why every single animal other than the ostracoderm is the placoderm’s closest relative.
Last updated April 7, 2007.