It was a huge predator about 5–6 metres in length and, like all rauisuchians, was equipped with a large head of long sharp teeth.

In Polonosuchus, the rostromedial foramen is on the medial surface of the maxilla, and the foramina for replacement teeth are not connected by a dental groove but are set together in a straight line, unlike in Teratosaurus.

From the skull are preserved both maxillae, premaxillae, nasals, prefrontals, palatines and quadrates, the left jugal, the right pterygoid, quadratojugal, surangular, articular, squamosal and lacrimal, and fragments of the dentary.

A ridge extending to form a suture with the palatine is present above the sixth, seventh and eighth dental alveoli.

The premaxillae are very similar to those of Postosuchus, but slightly smaller; the posterodorsal process is broken off, but sutures present on the nasal bones show it would have extended all the way up to the anterior border of the naris.

There is also a descending process of the lacrimal which forms most of the posterior border of the antorbital fenestra, with a noticeably striated ridge.

A small facet at its base forms part of the articulation with the basisphenoid, which is common for Triassic archosaurs.

[2] The centrum of the atlas vertebra is the only part preserved, and has a crescent shape and rounded anterior surface.

The axis has a triangular neural spine and relatively small prezygapophyses, at least compared to the stout postzygapophyses.

The caudal vertebrae have pronounced facets for the haemal arches, and tall plate-like neural spines.

The centra have smooth convex ventral surfaces, and as the vertebrae are fairly large, they probably come from the anterior part of the tail.

The three smaller plates are leaf-shaped and their articulatory processes are in a different place, indicating the presence of at least two distinct rows of medial dermal armour.