Nectridea is an extinct order of lepospondyl tetrapods from the Carboniferous and Permian periods, including animals such as Diplocaulus.

[4] A trace fossil known as Hermundurichnus fornicatus of a tetrapod resting on a lake bed may have been attributed to Diplocaulus or an animal like it.

This trace indicates that the underside of nectrideans was covered in small, diamond-shaped scales and that the "horns" of the skull were connected with the body by flaps of skin.

[5] There has been some controversy over the precise classification of Nectridea over the past century, and even whether it constitutes a valid monophyletic clade.

For example, Anderson (2001) positioned diplocaulids as close relatives of Aistopods with urocordylids and scincosaurids as progressively more primitive members of the group.

[6] The following is a cladogram from the Ruta et al. (2003): Batropetes fritschi Tuditanomorpha Microbrachis pelikani Hyloplesion longicostatum Odonterpeton triangulare Lysorophia Adelospondyli Aistopoda Urocordylidae Diplocaulidae Scincosauridae