The majority of these have been found in freshwater sediments, though such a large range suggests that they may have been able to enter saltwater.

It also had an internal joint between its neck vertebrae and the back of the skull, allowing for the mouth to be opened even wider.

As with all other arthrodires, Coccosteus had bony dental plates embedded in its jaws, forming a beak.

[3] Overall the creature looked similar to its gigantic cousin Dunkleosteus, save that its eyes were closer to the end of its snout than in its larger relative.

The cladogram below shows the phylogeny of Coccosteus:[4] Millerosteus minor Coccosteus cuspidatus Dickosteus threiplandi Watsonosteus fletti Protitanichthys rockportensis Plourdosteus canadensis Panxiosteus ocullus Janiosteus timanicus Harrytoombsia elegans Torosteus tuberculatus Torosteus pulchellus Mcnamaraspis kaprios Compagopiscis croucheri Trematosteus fontanellus Incisoscutum ritchiei Incisoscutum sarahae Rolfosteus canningensis Tubonasus lennardensis Fallacosteus turneri Camuropiscis laidlawi Latocamurus coulthardi Pachyosteomorphi