The skull of the bizarre mudpuppy (Necturus) under review

Necturus maculosus (Rafinesque 1818, Fig. 1) is the extant mudpuppy, a salamander with gill slits.

Strangely,
the upper tooth row is divided in three parts (Fig. 1). The short maxilla is fused to the premaxilla. The vomer is fused to the laterally exposed palatine. The ectopterygoid is ventral to the pterygoid. All jaw bones that reach the margin have large teeth.

On the palate,
the choana (internal naris, Fig. 1) is barely open and it does not have a posterior border. A central opening perforates the anterior palate. Otherwise the parasphenoid is wider than in any other taxon. It creates a nearly solid palate.

On the mandible,
both the dentary and the coronoid have teeth.

Online images
do not identify the maxilla, but label the entire set of fused bones a premaxilla. Sister taxa do not have such a long premaxilla. Similarly online images do not identify the palatine, but label the entire bone a vomer. Traditionally and in sister taxa vomers do not extend to the lateral skull. Thus, several skull bones here are reidentified based on homologs with sister taxa. Thus Necturus is not quite as bizarre as dissection guides indicate.

Postcranially,
pedal digit 5 is absent, distinct from all sister taxa. In the large reptile tree (LRT, 1471 taxa) Necturus nests between Rana, the bullfrog, and Andrias, the Chinese giant salamander.

References
Rafinesque CS 1818. The American monthly magazine and critical review 4: 41.

wiki/Necturus