This tiny amphibian was very similar to the Rachitomi, differing primarily in size. Other distinguishing characteristics include a cartilaginous, less ossified skeleton and a shorter skull. Clear traces of gills are present in many fossilized samples, hence the name.
Originally thought to have vertebrae distinct from rachitomous vertebrae, it was placed in a separate order named Phyllospondyli. Later analysis of growth stages showed increasing ossification in larger specimens, which showed that at least some of the species was the larval stage of much larger rachitomes like Eryops, while others represent paedomorphic species which retained the larval gills in adulthood.
There are four known species in the genus Branchiosaurus;
- Branchiosaurus gracilis
- Branchiosaurus pusillus
- Branchiosaurus salamandroides
- Branchiosaurus umbrosus