page_title: Polonosuchus
section_title: Skull
hierarchical_section_title: Polonosuchus / Description / Skull
caption_attribution_description: Polonosuchus skull bones, Museum of Evolution of Polish Academy of Sciences, Warsaw.
context_page_description: Polonosuchus is a genus of rauisuchian known from the late Triassic of Poland. 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. The legs were placed almost underneath the body, unlike most reptiles, which would have made it quite fast and a powerful runner. The appearance was very similar to that of the more known Postosuchus, of North America, and shared with the latter the ecological niche of the apex predator.
context_section_description: The maxillae are tall and laterally compressed, forming most of the borders of the antorbital fenestra (visible on the photo above). The palatal process extends anteroventrally and is very short. A ridge extending to form a suture with the palatine is present above the sixth, seventh and eighth dental alveoli. Small infraorbital foramina are located around the edge of the antorbital fenestra, near the teeth. At least eleven dental alveoli were present, although the total is not certain as both maxillae are broken off at the posterior ends. Small replacement teeth are visible above some of the alveoli, indicating it was probably a polyphyodont.
  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. The palatal processes of the premaxillae are incompletely preserved, but would almost certainly have articulated with those of the maxillae. There are certainly four alveoli present, with a small cavity which may be a fifth.
  The nasals have a long dorsoventrally compressed process which would have extended down between the maxilla and premaxilla. They also have a long anterior process with a triangular cross-section. The surface for articulation with the lacrimal is clearly visible on the right nasal.
   
  The lacrimal has a thick rugose ridge extending back from that on the nasal. Its lamellar part forms the posterodorsal border of the antorbital fenestra, and is articulated with the maxillae which form much of the rest of the borders. 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. This descending process would probably have contacted the jugal at its ventral end.
  The prefrontals are large triangular plates which overhang the orbits, with rugose lateral surfaces. All the surfaces which articulate with the other bones of the skull roof are narrow and oblique.
  The squamosal has five projections. Two of these bordered the superior temporal fenestra and met with the parietal and postorbital, which are not known. A hook-like ventral projection would have met the quadrate head, and a lateral projection would have overhung the quadratojugal. The fifth projection is broken off and missing.
  Much of the jugal is preserved, although not the anterior or ascending processes. The posterior process has straight margins. The ascending process had a triangular cross-section at the base, where it articulates with the pterygoid. The quadratojugal is only partial, with a broken dorsal edge. Its process for articulating with the quadrate is clearly visible, and that for the jugal is long and indented.
   
  The palatines have a robust anterior and fragile posterior. Relative to their overall length, the region between the choanae and the suborbital fossae is very long. An oblique vertical wall rises from the dorsal surface, separating part of the nasal fossa. There are two ridges which cross on the ventral surface.
  The pterygoid has a missing anterior ramus. Its posteroventral ramus has missing parts, but the centre is preserved and exhibits a cleft for the ectopterygoid. The quadrate ramus extends back with a narrow shelf on the ventral side. A small facet at its base forms part of the articulation with the basisphenoid, which is common for Triassic archosaurs.
  The quadrate has a rounded dorsal head which contacts the squamosal, and a high and narrow pterygoid ramus. There is a strong posterior ridge along the quadrate's main axis. Above the two parts of the mandibular condyle, there is a well-defined facet for articulation with the quadratojugal.
  The anterior parts of the dentary are preserved, up to the first eight teeth. The lateral faces bear a series of vascular foramina.
  The articular and surangular are fragmentary, and one of the few features preserved is a foramen for a branch of the facial nerve.
caption: Skull bones
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