Lepospondyli

Article By:

Anderson, Jason S. Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.

Last reviewed:2014

DOI:https://doi.org/10.1036/1097-8542.377900

An assemblage of diverse, extinct, small tetrapods found in rocks from the Mississippian to Permian periods (340–245 million years ago). In older Linnean classifications, Lepospondyli is a subclass of Amphibia, along with Labyrinthodontia (other Paleozoic tetrapods) and Lissamphibia (the modern amphibians). Recent analyses of interrelationships of all Paleozoic tetrapods have changed this view. Labyrinthodontia, for instance, has been found not to include all descendant lineages and has been abandoned as a technical name. However, research demonstrates that Lepospondyli includes all descendants of a single common ancestor (a clade), and continues to be used in both Linnean and phylogenetic classifications. Anatomical features uniting lepospondyls include a lack of labyrinthine infolding of tooth dentine, paired palatal fangs and replacement pits, absence of an otic notch in the back of the skull, a small forwardly oriented projection on the first vertebra (reduced in some), and single spool-shaped vertebrae (see illustration). However, these features are also characteristic of juvenile or small amphibians. Since all lepospondyls are small, a few specialists still question the group's integrity. See also: Amphibia; Lissamphibia

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