[2] Rugarhynchos was a close relative of Doswellia and shared several features with it, such as the absence of an infratemporal fenestra and heavily textured skull bones.

However, it could also be distinguished by many unique characteristics, such as a thick diagonal ridge on the side of the snout, blunt spikes on its osteoderms, and a complex suture between the quadratojugal, squamosal, and jugal.

Non-metric multidimensional scaling and tooth morphology suggest that Rugarhynchos had a general skull anatomy convergent with some crocodyliforms, spinosaurids, and phytosaurs (particularly Smilosuchus).

[2] The only known specimen of Rugarhynchos is NMMNH P-16909, a partial skeleton consisting of several bones scattered over a small area.

A fragment originally described as an articulated parietal and postorbital was later considered part of the palate.

The only preserved portion of the jaw is a left surangular, although a large right pterygoid fragment was originally considered an articular.

[1][2] The top of the Bluewater Creek Member was separated from overlying strata by a distinct tuffaceous sandstone layer (the "SMC bed") at Six Mile Canyon.

The genus name is derived from Latin words for "wrinkle" and "nose", in reference to the wide variety of rough ridges on its snout.

Four enlarged teeth in the front half of the tooth row are covered by a convex extension, giving the maxilla a sigmoid lower edge akin to that of "robust-morph" phytosaurs.

The rear of the nasals are incised by the triangular front edge of the frontals, creating a wedge-shaped suture also seen in Proterochampsa.

One autapomorphy (unique distinguishing feature) of Rugarhynchos is the presence of a thick diagonal ridge on the side of the snout.

Its front edge formed the rear rim of a supratemporal fenestra, a hole in the upper part of the skull behind the orbits.

The quadrate is steeply angled to the rest of the skull (like Chanaresuchus and Doswellia) and also has a large, hooked upper portion (like Vancleavea and allokotosaurians).

This is similar to Proterochampsa and Chanaresuchus, though insufficient data on basal archosauriform palates prevents comparison to many other taxa.

Unique to Rugarhynchos, there is a cup-shaped depression on the rear edge of the surangular below where it connects to the articular bone.

They were roughly square-shaped and ornamented by large circular pits which radiated from the center of each plate, like other doswelliids.

Also in line with doswelliids, the osteoderms articulate with each other via a smooth and flat front edge rather than spines or notches.

The pits are shallower and the upper surface of the osteoderm has a central blunt spike-like eminence rather than a raised keel.

More irregularly shaped osteoderms near the skull may have connected to form a "nuchal shield" similar to that of Doswellia.

[1][2] To test its relations to other early archosauriforms, Rugarhynchos was placed into a phylogenetic analysis derived from an earlier study by Ezcurra et al.

Instead of having a clean break between proterochampsids and doswelliids, the bayesian analysis suggested that Proterochampsidae in its traditional form was paraphyletic rather than monophyletic.

The results of the bayesian analysis are shown below:[2] Proterosuchidae Fugusuchus Sarmatosuchus Cuyosuchus Erythrosuchidae Dorosuchus Asperoris Euparkeria Vancleavea Litorosuchus Proterochampsa Jaxtasuchus Doswellia Rugarhynchos Cerritosaurus Tropidosuchus Pseudochampsa Gualosuchus Chanaresuchus Rhadinosuchus Avemetatarsalia Pseudosuchia