Therapsida: Biarmosuchia: Biarmosuchidae / Eotitanosuchidae

Known from two skulls and postcrania, Biarmosuchus was a medium-sized predator, similar in size to a large dog. It was a lightly built, probably agile animal that would have fed on smaller tetrapods. Their legs are quite long, and the animals were probably quite agile in spite of their size.

Until recently only two genera -- each of one species, are recorded -- Eotitanosuchus and Ivantosaurus. The latter is known from only two jaw fragments, and seem to be very similar to Eotitanosuchus. Tatarinov (1999) has recently described a new species and genus of eotitanosuchian.

Known from a single large skull without a lower jaw, Eotitanosuchus was without doubt a dominant animal of its environment. Found preserved in flood deposits (once coastal bogs) containing many skeletons of estemmenosuchids, it has been suggested that this large predator was an excellent swimmer, possibly semi-aquatic or frequenting marshy ground. This however is just speculation. The name means "Dawn giant crocodile", which is a bit misleading because although a large preditor it was not huge. A catalogue of a Russian dinosaur exhibition (Vickers-Rich and Rich, 1993) states that the oft-illustratred skull (about 35 cm long) is from a juvenile, an adult has a skull about 1 meter long. I have not found any other information on this, apart from the reference to the eotitanosuchid Ivantosaurus ensifer, known from a jaw fragment from the same locality (Sigogneau-Russell 1989 pp.29-30). So It seems what is being stated here is Ivakhnenko's thesis that this is the adult form of Eotitanosuchus/Biarmosuchus. It is just as likely that this was a distinct animal, and that these were three related forms of different sizes. In any case, assuming that the rest of the creature was in proportion, Ivantosaurus would have been the largest carnivorous therapsid known, exceeding in size even the largest Late Wordian/early Capitanian anteosaurs.

The holotype is a crushed and deformed skull. Additional skull and skeletal material is known. There are 8 or 9 small and flattened postcanines in the jaw. Eotitanosuchus is found preserved in flood deposits (once coastal bogs) containing many skeletons of estemmenosuchids.

Holotype and only known material, maxilla and quadrate found in association and in their respective natural positions.

Either a giant individual of Eotitanosuchus (if E. olsoni is a juvenile this would therefore be a large adult), or, perhaps more likely, a distinct species. This is a very large animal (length would have been around 6 meters). Maxilla short and high. Two upper canines, long, and with their axes inclined forward. It is not clear if one of the canines is a replacement tooth. Sigogneau-Russell (1989) seems to think this is unlikely, which would make this a quite different animal from Eotitanosuchus. As with the therocephalian "family" Lycosuchidae, these may simply be replacement canines. There are few known animals, living or extinct, with two sets of canines (it would be a very inefficient chewing mechanism)

Based on an incomplete skull

The snout is relatively short, the canines are massive and long, the parietals are thickened, and the mandibular symphysis is extremely high. The palatal teeth cover the pterygoids and palatines and are not concentrated on special bony tubercles.