was a genus of gigantic pachycormid fish that lived in the oceans of the Mesozoic. Largely considered to be one of the largest bony fish to ever live, this behemoth could grow up to 32 feet long (some estimates put it at 53 feet). This giant fish although it had alot of teeth was probably a gentle filter feeder like extant basking sharks. leedsichthys had no recorded predator with specimens known to escape the Liopleurodon which was the top predator of the time, their large and powerful tail probably helped them out run and out maneuver the giant reptile.
Pycnosteus is an extinct genus of jawless fish from the Devonian period. these ancient aganathans probably cruised through the primal vegetation, eating any small invertebrates it displaces.