Temnospondyli became a commonly used name at the turn of the century . Paleontologists included both embolomeres and rhachitomes in the group . Cope 's Ganocephala and Labyrinthodonta fell out of use . In 1919 , British paleontologist D. M. S. Watson proposed that the evolutionary history of these large amphibians could be seen through changes in their vertebrae . Embolomerous forms in the Carboniferous graded into rhachitomous forms in the Permian , and finally into stereospondyls in the Triassic . More importantly , Watson began using the term Labyrinthodontia to refer to these groups . The name Temnospondyli was rarely used in the decades that followed . Swedish paleontologist Gunnar Säve @-@ Söderbergh removed embolomeres from the group , narrowing its scope to rhachitomes and stereospondyls . His classification of labyrinthodonts was based heavily on characteristics of the skull rather than the vertebrae .