Polonosuchus silesiacus Sulej, 2005

Brusatte, Stephen L., Butler, Richard J., Sulej, Tomasz & Niedźwiedzki, Grzegorz, 2009, The taxonomy and anatomy of rauisuchian archosaurs from the Late Triassic of Germany and Poland, Acta Palaeontologica Polonica 54 (2), pp. 221-230 : 228

Polonosuchus silesiacus Sulej, 2005

Holotype: ZPAL AbIII/563, series of cranial and axial elements, including left and right maxillae, from a single associated individual.

Type horizon: Late Carnian (Late Triassic).

Type locality: Krasiejów, Opole Silesia, Poland (for further details, see Sulej 2005 and Dzik and Sulej 2007).

Emended diagnosis.—Rauisuchid rauisuchian archosaur with the following combination of characters: thick and swollen rim delimiting the antorbital fossa on the maxilla, which continues caudally onto the jugal; absence of rostral ramus of maxilla; rugose ridge on the lateral surface of the skull roof (nasals, lacrimal, palpebral, postorbital, squamosal); large triangular palpebral ossification dorsal to the orbit (previously identified by Sulej 2005 as an enlarged prefrontal, but clearly a separate ossification); deep pit on the caudodorsal corner of the lateral surface of the squamosal; subdivided lower temporal fenestra. Differentiated from Teratosaurus by: a medial groove for the dental lamina that is subtle and entirely absent in some places; groove for the dental lamina (and associated tooth replacement foramina) oriented in a straight line across its entire length; first maxillary alveolus approximately equal in size to subsequent alveoli; ventral margin of the maxilla sinuous and highly convex in outline; the caudoventral groove on medial surface of the palatal process short and poorly defined; a prominent and sharply defined caudodorsally arched ridge extending from the base of the palatal process; and a deep fossa present dorsal to the palatal process. Differentiated from Postosuchus kirkpatricki by: ventral margin of the maxilla sinuous and highly convex in outline; first maxillary alveolus approximately equal in size to subsequent alveoli; absence of fossa on the dorsal surface of the nasal; absence of dorsoventral expansion of the rostral end of the dentary.

Remarks.— The entire preserved skeleton of the holotype specimen of Polonosuchus silesiacus , including the maxilla, was described in detail by Sulej (2005) and does not warrant redescription here. Overall, the maxilla of Polonosuchus is very similar to that of T. suevicus , but several differences are apparent (see above). Although Polonosuchus has been separated from Teratosaurus , it is possible that further discoveries of Teratosaurus material may reveal characters shared by the two genera, thus supporting a sister taxon relationship. If this is the case, then Polonosuchus could be transferred back to Teratosaurus , although this is a subjective decision if the two are sister taxa. A detailed description of all previously described material of Polonosuchus silesiacus , as well as and new cranial and postrcranial bones, is in preparation by the authors.