It's 2 sided you play the dinosaurs one round then the humans the next. It is not a fighting game like Primal Rage (that game was great!), it is an FPS. It's really fun, and the best thing is that playing the humans you really get the survival feeling of I better stick with my friends or a raptor is going to jump on my back and tear my throat out (btw - that is a real attack the raptor has).
As a dinosaur it just feels right, you can stomp the humans to kill them (as T-Rex), but they are smaller and move into buildings and can get away, so you need the smaller dinosaurs to help out.
Honestly, my favorite is the Carnotaurus as the dinos, and the firestarter (armed with a chainsaw and flame thrower) as the humans. The sides are not balanced in the typical fps way (i.e. there is no real sniper for the dinos, no flyer for the humans for example) but it is immensely fun.