Darriwilian first appearances

Gnathostomata (; from Ancient Greek: ('''') 'jaw' + ('''') 'mouth') are jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all extant vertebrates, including all living bony fishes (both ray-finned and lobe-finned, including the terrestrial tetrapods) and cartilaginous fishes, as well as extinct prehistoric fish such as placoderms and acanthodians. Most gnathostomes have retained ancestral traits like true teeth, a stomach, and paired appendages (pectoral and pelvic fins, limbs, wings, etc.). Other traits are elastin, horizontal semicircular can

Sphaerexochus is a genus of trilobites from the Middle Ordovician to Late Silurian (468.1 to 418.7 Ma) of Asia, Australia, Europe, and North America.