The Eotitanosuchids were large to very large (upto 6 meters long, weights of upto 500 kg or more) preditory therapsids of the middle Permian ( Wordian epoch). Like the Biarmosuchia they are rather poorly known, although they were probably more common than their few remains indicate. They seem to be more advanced than the Biarmosuchia in that the temporal opening behind the eye socket, although small, is still somewhat larger than the biarmosuchians, being expanded in the upper rear (posterodorsal) margin, allowing the area of attachment of the adductor muscles that closed the lower jaw (Musc. adductor mandibulae externus) to be visible from the dorsal (top) view looking down. Hence the Eotitanosuchian bite was stronger and more efficient than the Biarmosuchian bite, and tended more towards the later therapsid condition.
For this reason paleontologists see the the Eotitanosuchids as transitional between the Biarmosuchids and the higher Therapsids. They may indeed be so, but I think it is just as - if not more - likely that features of a larger temporal opening and hence increased muscle mass and biting power evolved simultaneously, among a number of early therapsid groups, due to intense competition for food and other resources. One must be very wary in applying cladistic methodology on characteristics that are likely to evolve simultaneously among many competing lineages.
It is interesting that in other respects the Eotitanosuchians are more primitive - they were the least modified in their jaw apparatus from their sphenacodontid ancestry and appear to have lacked a key theriodont feature-the streptostylic (movable) quadrate.
Although often grouped with the Phthinosuchidae and the Biarmosachidae, Eotitanosuchus is quite distinct from both and may be closer to the Gorgonopsia. However, Gorgonopsian specialisations are either not present in Entitanosuchus or, as is more often the case, the state of the characters is unknown. This genus is characterised by many primitive features of the septomaxillary, the postorbital, the parietal, the interparietal, the basioccipital, the quadrate rami of the pterygoid and the vomers of the skull. The length of the dorsal process of the premaxillary (front jawbone) and the postorbital twisting (rear side of the skull) constitute specializations that indicate it is not a direct Gorgonopsian ancestor. These features however are shared by the brithopodid and biarmosuchid lineages.
The Eotitanosuchids can thus be best understood as one of a number of lineages of competing early therapsids that flourished during Middle Permian time.
Ecological niche/Guild: medium-sized to very large to terrestrial (and semi-aquatic?) carnivores
Modern equivalent: canid???... crocodilian???
Time: middle Permian (late? Roadian or early Wordian epoch)
Distribution: although so far fossil remains are known only from eastern Russia it is likely these animals had a much wider, probably worldwide ( Pangea) distribution
preferred food: other tetrapods, large freshwater fish?
length: about 2 to 6 meters long (skull: 35 cm to upto 1 meter)
weight: about 30 kg to 600 kg or more
Metabolism: partially endothermic and gigantotherms (Homeotherms)
Predators: none (top of food chain)
Ancestor: Basal Therapsid (proto-Biarmosuchian ancestor?)
Replaced: Large Sphenacodontids
Replaced by: Brithopodids
Descendents: None - although proto-Eotitanosuchids may or may not have given rise to Gorgonopsid and/or Brithopidids
Taxonomic status - Monogeneric/monospecific? Family
Until recently only two genera - each of one species, are recorded - Eotitanosuchus and Ivantosaurus. The latter is known from only two jaw fragments, and would seem to be very similiar to Eotitanosuchus. Personally I think it is unwise to erect a new genus on fragmentary material, and it is quite likely that this is just another species of Eotitanosuchus. L. P. Tatarinov, of the Paleontological Institute, Russian Academy of Sciences, has recently described a new species and genus of eotitanosuchid
Eotitanosuchus olsoni Chudinov 1960
The holotype is a crushed and deformed skull. Additional skull and skeletal material is known. A lot of this is juvenile material, such as the famous 35 cm long skull displayed in The Russian Dinosaur Exposition and shown here. An adult skull would likely reach about 1 metre in length, which would give an overall length of some 6 meters. 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, and it is likely that this large predators was an excellent swimmer, possibly semi-aquatic or frequenting marshy ground. Ther legs are quite long, and the animals were probably quite agile in spite of their size
Ivantosaurus ensifer Chudinov 1983 ? = Eotitanosuchus ensifer (Chudinov)Locality: Echovo locality, Ocher Province, Perm Region, eastern European Russia
Probably a giant individual of Eotitanosuchus (if E. olsoni is a juvenile this would therefore be a large adult), although it may or may not be a different species to E. olsoni. This is a very large animal (legth would have been around 6 meters). Maxillary short and high. Two upper canines, long, and with their axis inclined forward. It is not clear if one of the canines is a replacement tooth. Sigogneau-Russell (p.30) seems to think this is unlikely, which would make this a quite different animal to Eotitanosuchus. Personally I think (as with the therocephalian "family" Lycosuchidae) that one of these are replacement canines. As far as I am aware there is no known animal living or extinct with two sets of canines (it would be a very inefficient chewing mechanism)
Kamagorgon ulanovi Tatarinov 1999Locality: Sokol locality, Udmurtia, Western part of the Middle Urals, Perm region, Russia
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.
|some Links and References|
Denise Sigogneau-Russell, "Theriodontia I - Phthinosuchia, Biarmosuchia, Eotitanosuchia, Gorgonopsia" Part 17 B I, Encyclopedia of Paleoherpetology, Gutsav Fischer Verlag, Stuttgart and New York, 1989
Peter K. Chudinov, "New Facts about the Fauna of the Upper Permian of the USSR", Journal of Geology, 1965, 73:117-30
Everett C. Olson, "Late Permian Terrestrial Vertebrates, USA and USSR", Transactions of the American Philosophical Society, Philadelphia, vol 52 part 2, 1962
Eotitanosuchus olsoni - same content as preceeding page, but bigger photo
Stars of the Show - includes Eotitanosuchus
L. P. Tatarinov, A New Eotitanosuchid (Reptilia, Therapsida) from the Kazanian Stage (Upper Permian) of Udmurtia Paleonotological Journal - Vol. 33, No. 6, 1999
M. F. Ivakhnenko, Biarmosuches from the Ocher Faunal Assemblage of Eastern Europe, Paleonotological Journal - Vol. 33, No. 3, 1999
Palaeos Page (incorporates some of this material, plus a lot of additional material)