Middle Silurian to Late Devonian | image = Cephalaspis tenuicornis.jpg | image_caption = Cephalaspis species | regnum = Animalia | phylum = Chordata | subphylum = Vertebrata | unranked_classis = Cephalaspidomorphi | classis = Osteostraci | subdivision_ranks = Orders | subdivision = Cephalaspida Zenaspida Kiaeraspidida Benneviaspida Thyestiida }} The class Osteostraci ("Bony Shields") was a group of bony-armored jawless fish, termed "ostracoderms", that lived in what's now North America, Europe a… (More on Osteostraci)