Montag, 29.01.2018, 17:15, Hörsaal Geologie. Dr.Oskar Bremer, Uppsala University, "Early fishes, old bones". The majority of vertebrates today are represented by those with jaws (gnathostomes) including chondrichthyans (sharks, rays, and ratfishes) and osteichthyans (bony fishes and tetrapods), while jawless vertebrates are only represented by the cyclostomes (hagfishes and lampreys). This division was largely established in the Devonian Period (419–359 mya), often called the “Age of Fishes”, when gnathostomes increased in abundance and diversified to fill a wide variety of trophic roles.