Given the task definition and input, reply with output. Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.

Fish reached substantial diversity during this time , leading the Devonian to often be dubbed the '' Age of Fish '' . The first ray - finned and lobe - finned bony fish appeared , while the placoderms began dominating almost every known aquatic environment . The ancestors of all four - limbed vertebrates ( tetrapods ) began adapting to walking on land , as their strong pectoral and pelvic fins gradually evolved into legs . In the oceans , primitive sharks became more numerous than in the Silurian and Late Ordovician .
Devonian