Question

Compare and contrast in essay format the anatomical features of the three modern amphibian groups to each other and to their extinct ancestors the Temnospondyli and before them the Ichthyostegalia.

Answer 1

temnospondyls were classified according to the structure of their vertebrae. Early forms, with complex vertebrae consisting of a number of separate elements, were placed in the suborder Rachitomi, and large Triassic aquatic forms with simpler vertebrae were placed in the suborder Stereospondyli. With the recent growth of phylogenetics, this classification is no longer viable. The basic rhachitomous condition is found in many primitive tetrapods, and is not unique to one group of temnospondyls. Moreover, the distinction between rhachitomous and stereospondylous vertebrae is not entirely clear. Some temnospondyls have rhachitomous, semirhachitomous, and sterospondylou

Ichthyostegalia is an order of extinct amphibians, representing the earliest landliving vertebrates. The group is thus an evolutionary grade rather than a clade.While the group are recognized on having feet rather than fins, most, if not all, had internal gills in adulthood and lived primarily as shallow water fish and spent minimal time on land.