The family was named by English naturalist Richard Lydekker in 1889 and includes the well-known genera Urocordylus and Sauropleura, as well as several others based on less-complete material.
[1] Urocordylids belong to a large group of Paleozoic amphibians called lepospondyls, which are distinguished from other early land vertebrates by their simple spool-shaped vertebrae.
Urocordylids have traditionally been considered the most primitive nectrideans because they lack some of the more unusual features of other members of the group, such as the tabular horns of diplocaulids.
The analysis of Ruta et al. (2003), for example, places the Urocordylidae as the closest relatives of a group of legless lepospondyls called the Aistopoda, while other nectrideans fall into a more basal position on the evolutionary tree.
Below is part of the cladogram from Ruta et al.:[2] Batropetes fritschi Tuditanomorpha Microbrachis pelikani Hyloplesion longicostatum Odonterpeton triangulare Lysorophia Adelospondyli Scincosauridae Diplocaulidae Urocordylidae Aistopoda