In the Carnian stage of the Late Triassic ( 228 @.@ 0 - 216 @.@ 5 Mya ) , capitosauroids were joined by the superficially very similar Metoposauridae . Metoposaurids are distinguished from capitosauroids by the positioning of their eye sockets near the front of their skulls . Another group of stereospondyls , the plagiosaurs , had wide heads with external gills , and adapted to life at the bottom of lakes and rivers . By this time , temnospondyls had become a common and widespread component of semiaquatic ecosystems . Some temnospondyls , such as Cryobatrachus and Kryostega , even inhabited Antarctica , which was covered in temperate forests at the time .