adaptation of Ophiacodon, supposedly because the hindlimbs would have been used to propel it through water. Several of these features are no longer thought to be evidence of an aquatic lifestyle; for example, broad claws are seen in most early tetrapods, even those that are known to have been almost exclusively terrestrial, and the long hindlimbs of Ophiacodon would not have been an effective means of propulsion because the feet were still relatively small and had little surface area over which to form a paddle. Analysis of the vertebrae of Ophiacodon indicate that it was most likely terrestrial and spent little time in water. A paleobiological inference model for the femur likewise suggests a terrestrial lifestyle for Ophiacodon, even though the rather thick cortex might also suggest amphibious, rather than truly terrestrial habits. Skeletons of Ophiacodon show a fast growth pattern called fibrolamellar bone (FLB), suggesting at least partial warm-bloodedness. The FLB pattern is also found in birds and mammals. References Ophiacodontids Prehistoric synapsid genera Carboniferous synapsids Cisuralian synapsids of Europe Cisuralian synapsids of North America Carboniferous North America Permian North America Pennsylvanian genus first appearances Cisuralian genus extinctions Taxa named by Othniel Charles Marsh Fossil taxa described in 1878