Input (grade 13): The first armored agnathansâ "the Ostracoderms, precursors to the bony fish and hence to the tetrapods (including humans) â" are known from the middle Ordovician, and by the Late Silurian the agnathans had reached the high point of their evolution.
Output (grade 8): Not to be confused with the Osteichthyes ("bony fish"), who were ancestors of the bony fish, and hence of tetrapods (including human beings). By the upper Silurian the Agnathans had reached the high point of their evolution.