The Tapinocephalidae were an advanced family of giant herbivorous Dinocephalia (adult weight from about 500 to 1000 kg, possibly upto 1.5 or 2 tonnes in the largest forms (Tapinocephalus atherstonsi)) that are known from both Russia and South Africa, and in all probability had a worldwide (Pangean) distribution. The trend towards giantism, so typical of many of the dinocephalians, was characteristic of even the earliest known members of this family. Along with Pareiasaurs, these were the "heavies" of the Middle Permian. They flourished briefly during the Wordian and Capitanian ages, radiating into several lineages, existing simultanoeusy, and differing mainly in details of the skull and (to an even less degree) the skeleton. It is not clear how such similar animals could each find their own ecological niche, but such was obsviously the case. There is a parallel here with the hadrosaur and ceratopsian dinosaurs of the late Cretaceous. The cause of their abrupt extinction is not clear, since other smaller animals, and even the semi-aquatic Parieasaurs, were not affected. Quite probably, like the extinction of the late Plesitocene megafauna, a number of factors were involved.
The tapinocephalian skull is massive in construction, and either long-snouted (e.g. Struthiocephalus) or high and short (e.g. Moschops). Very often the top of the head is rounded the bones of the forehead elevated into a sort of dome or boss, in the middle of which was a large pineal opening. In some specimens this boss is of only moderate thickness, while in others it has become greatly thickened into a huge mass of bone (pachyostosis). It has been suggested that these animals engaged in intra-specific head-butting behaviour (left), presumably for territory or mates. A similar thickening of the skull occurs in pachycephalosaur ("boneheaded") dinosaurs, and it is speculated that all these animals practised head-butting behaviour like modern goats and bighorn sheep, and late Eocene Titanotheres.
In keeping with their innofensive vegetarian lifestyle, the chisel-edged teeth are undifferentiated, lacking canines, and rather peglike. in maturity the teeth have a talon and a crushing heel and the upper and lower teeth of the whole battery intermesh.
The body is deep and capacious, allowing for a developed herbivore gut. The shoulders are much higher than the pelvic region, so that the back slopes, giraffe-fashion, from neck to tail. This seems to imply that they fed on vegetation of about a meter or more from the ground
The limbs are heavy, with sturdy forelegs that sprawled out to the sides, while the longer hindlegs were placed directly under the hips (the dicynodonts had the same posture). The feet are broad and short.
There is some disagreement over whether these animals lived in dry upland environments (Colbert), swamps, or either, depending on the species or tribe
There is no doubt that the Tapinocephalians occupied different ecological niches. However, the tendency of earlier writers like Gregory and Boonstra to consider them semi-aquatic wallowers reminds me of the old fable of the sauropods consigned to the swamps because their limbs were too clumsy and their bodies too heavy for them to exist on dry land. In fact if they were head-butters it is unlikely they could have been clumsy swamp wallowers, since head-burtting implies some degree of mobility.
Boonstra suggests that Tapinocephalines and Struthiocephalines were semi-aquatic, and Moschopines terrestrial. While I don't buy the semi-aquatic hypothesis (it seems that the ponds and lakes were already inhabited by Pareiasaurs in any case), it is quite likely that some Tapinocephalid species may have frequented pond margins, feeding on soft vegetation, others preferred dry uplands
Gregory 1926 considered that dinocephalians were aquatic animals, the wide hands and feet and the extensive fore and aft reach being useful for propelling the animal through water and the massive forehead being an advantage in diving. He suggested that the pineal organ might have been phototropic, helping the animal to orient itself relative to the surface of the water.
Tapinocephalines were seen by Boonstra 1956 as semi-aquatic animals. The cumbersome body, poor locomotor apparatus and feeble lower jaw and massive cranium all suggested to him that these animals could not have fed efficiently on land on tough vegetation. Instead he presented them as wallowers, being buoyed up by water, feeding on soft marsh vegetation.
Rescuing the Tapinocephalids from a life of antedilievian wamp-wallowing, Bakker 1975, 1986 argued that bone-histology, geographic distribution, and predator-prey relationships showed that these were active, fully terrestrial and at least partially endothermic animals, midway between the ectothermic pelycosaurs and the fully endothermic theriodonts.
Others like McNab and Geist suggest that the Tapinocephalids were better considered inertial homeotherms, with the large barrel-like body and short tail being the most efficient surface for conserving heat.
My own position, for what it is worth, is that these were all fully or at least mostly terrestrial animals, although possibly (but not necessarily) evolving from semi-aquatic ancestors (many of the Russian dinocephalians seem to have lived a semi-aquatic lifestyle). They were inertial homeotherms, not endotherms, and rather than the ungainly antedilevian bumblers, were well adapted, successful animals that doominated their environment. Their demise was the result of a sudden environmental stress, perhaps a combination of climatic and vegetation change and exotic disease, which naturally hit these big, K-selected (slow to reproduce) creatures hardest.
Boonstra originally (1963) recognised five subfamilies, the Moschosaurinae, Struthiocephalinae, Tapinocephalinac, Moschopinae and Riebeeckosaurinae, later reducing these to four, in about 15 genera (13 from the Karoo of South Africa). King reduced the family Tapinocephalidae to the subfamily Tapinocephalinae of the family Titanosuchidae, and correspondingly made the subfamilies tribes (the next linnean ranking down), synonymising the Moschopini with the Tapinocephalini. No attempt was made to reduce the number of genera or species. ***name*** described a new basal Tapinocephalid, Tapinocaninus, which is the sister group to all other Tapinocephalids. While it is not always wise to combine the cladistic and linnean methodologies, in this instance it would be appropriate. I would suggest that Tapinocaninus be given its own paraphyletic family, the "Tapinocanininae", as distinct from the rest of the Tapinocephalinae, and that both of these be included under the reinstated Tapinocephalidae. I also feel that the number of genera and species recognised is clearly excessive, in view of the degfree of individual variation, and the fact that many taxa are known only from a single skull. I therefore have synonymised a number of taxa, citing individual variation, growth stages, incomplete material, and sexual dimorphism.
Primitive ancestral members of the family - transitional between the Titanosuchidae and Tapinocephalidae proper. Very large herbivores or omnivores. Wordian age. There is a single genus and species, Tapinocaninus pamelae
Tapinocaninus pamelaeHorizon: Eodicynodon Zone, Karoo deposts, Beaufort series, South Africa
Comments: More information at The Bernard Price Institute (BPI) Museum
The most advanced members of the family. Very large herbivores. Capitanian age only
Tapinocephalids with a long fairly strong snout and with moderate pachyostosis. The male possess a large naso-frontal boss which is used in intraspecific combat. There is probably only one known species
Brink 1957 suggests that Struthiocephalus fed in or near water, the teeth being used for rooting up, gathering and grasping plant matter. Boonstra 1965 likewise considered that Struthiocephalus fed on soft vegetation, possibly under water. He suggetsed the postcraoial skeleton possibly showed adaptations to living in marshy conditions (but see my earlier comments), and the bone surface around the nostril might indicate the presence of a fleshy valve present used for closing off the nostril under water
Suggested valid species:
Struthiocephalus whaitsi (= Struthiocephaloides)
Struthiocephalus whaitsi Haughton, 1915aHorizon: Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
Comments: The long-snouted Struthiocephalus whaitsi would seem to be the only genus and species of this taxon. This animal has the largest head of any Tapinocephalid. There area large number of synonymns. Struthiocephalellus is apparently a juvenile of Struthiocephalus. Boonstra showed that the seven named species of Struthiocephalus represent a growth series and are hence synonyms of the first described species, whaitsi.
Struthiocephalus is characterised simply by a naso-frontal boss in mature specimens, whilst the very similar genus Struthiocephaloides lacks this character. This would almost certainly be a sexually dimorphic character, which could be consists with its role in intraspecific combat. Barghusen 1975 considers would be more effective in flank butting than be. In head combat the horn would be deflected by the opponent's head and contact would be lost, but in flank butting the horn would concentrate the blow. Both "Struthiocephalus" and "Struthiocephaloides" have the same stratigraphic range - Lower to Middle Tapinocephalus Zone
Of the remaining two monospecific genera, Struthionops intermedius known from a single skull, possesses a naso-frontal boss moderate pachyostosis and a fairly short snout. Possibly this is a variant of another species. On the basis of the shorter snout, Gillian King includes this species among the Tapinocephalini.
Taurocephalus lerouxi, known from a single skull, has a fairly strong snout and twenty teeth in teh upper jaw (more than usual for Tapinocephalids). Since tooth count tends to vary greatly among individual Dinocephalias, and since again only this is also likely a variant individual, most probably Struthiocephalus
The remaining species Moschosaurus longiceps, Haughton is known from a single small and lightly built skull about 25 cm. long from the Upper Tapinocephalus Zone. It was originally placed in its own family, the Moschosauridae, and considered a good ancestral or primitive form (despite its late date). Later, Boonstra identified it as a juvenile Struthiocephalus.
The tapinocephalines are medium to very large tapinocephalids in which the snout is short to moderate in length; pachyostosis ranges from medium to extreme. I have very tentatively divided this tribe into two subtribes, equivalent to the two subfamilies of Boonstra.
The Subtribe Tapinocephalina is the same as Boonstra's Subfamily Tapinocephalinae. These are large tapinocephalids, including the giant Tapinocephalus atherstonsi, which Boonstra suggests may have attained a weight of nearly two tons. Pachyostosis is very strongly developed in these forms, and there is either a prominent nasal frontal boss (Keratocephalus) or a greatly swollen frons Tapinocephalus
Suggested valid species:
Keratocephalus moloch (least derived?)
Mormosaurus seeleyi (synonym of Keratocephalus???)
Tapinocephalus atherstonsi (= Phocosaurus megischion) (most derived?)
Tapinocephalus atherstonsiHorizon: Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
Comments: Tapinocephalus atherstonsi is the only species of this genus. It is known from a number of skulls and postcranial bones. The skull is large with a heavily pachyostotic skull roof, a massive bony frons and a short weak Moschops-like snout. Taurops is a synonym. This succesful animal survived right until the end of the Tapinocephalus zone. Phocosaurus megischion differs from Tapinocephalus only in that the transition from the frons to the snout is not abrupt. In view of the fact that it too continues until the upper Tapinocephalus zone, I would tend to see this as synoymous with Tapinocephalus zone, the differences being sexually dimorphic
Keratocephalus molochHorizon: Lower and Middle Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
Comments: Keratocephalus moloch, known from a number of greatly variable skulls, along with postcrania, from the Lower and Middle Tapinocephalus zone, shows considerable variability in the pachyostotic development. It may be not as derived as Tapinocephalus. The naso-frontal boss is raised into a sort of horn (hence the name - "horned head") and the length of the snout varies greatly. This in itself thows doubt on Boonstra's distinction between short and long-snouted forms. Pelosuchus, known only on the basis of postcranial features, is a synonym.
Mormosaurus seeleyi is characterised by a two morphologically different skulls. Unlike Tapinocephalus, the snout is fairly long and the pachyostosis moderate. Perhaps these are juveniles of Keratocephalus
Medium-sized to large tapinocephalids with a short snout running up to the front in an even curve. As with other Tapinocephalini the cranial roof is moderately to very greatly thickened by pachyostosis. Booonstra considered this taxon a subfamily, but Gillian King does not consider the differences sufficient to distinguish this taxon from the Tapinocephalines. I have compromised and made them a subtribe. Probably all these species should belong in only a single genus. With the possible exception of Delphinognathus (the location information of the single known skull is however uncertain) all the Moschopines died out at the end of the Lower Tapinocephalus Zone time.
It has been suggested that Moschopines fed on relatively unnutritious food such as cycad stems which would be torn up from the ground using the powerful muscles of the neck and jaws. This helps explain the sloping giraffe-like back, since they might grab the stem from above. They may also have fed on fruitifications taht grew a meter or more from the ground
Suggested valid species:
Ulemosaurus svigagensis (least derived?)
Moschops capensis (=Delphinognathus? = Avenantia?)
Criocephalus vanderbyli (most derived?)
Ulemosaurus svigagensis Riabinin 1938Locality:Kamennyi Valley, near Isheevo, Cis-Urals, Perm region, Russia
Comments: Ulemosaurus is a large Moschops-like form from Russia; it is probably similar enough to be included as a separate species of Moschops. Despite its advanced characteristics, it lived slightly before the Karoo forms, showing that the Moschopines, and indeed the Tapinocephalidae in general, had already attained their acme but early Capitanian time. Boonstra 1963 considers this taxon midway Moschops and Delphinognathus, and not as advanced as Moschops. In asmuch as Delphinognathus may turn out to be synonymous wth Moschops anyway, this species may consiute a good ancestral or near-ancestral type for the very similar but slightly later Moschops, despite the fact that the two taxa come from opposte ends of Pangea (many animal species were probably cosmopolitan)
Moschops capensisHorizon: Lower Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
Comments: Moschops (with synonyms Moschoides, Agnosaurus, Moschognathus and Pnigalion) is distinguished by a strongly pachyostosed skull with a broad intertemporal region and greatly reduced temporal fossae. There are two species - capensis and koupensis - that are known from good material, and two species - whaitsi and oweni - of doubtful validity. It may be that M. capensis and M. koupensis are not distinct pecies at all, but sexually morphs, and in any case they occupy the same stratigraphic range. The species Delphinognathus conocephalus, known from a single weathered skull, has a conical boss on the parietal surrounding the pineal foramen, and in which there is moderate pachyostosis. Boonstra suggests this may simply be a young specimen of Moschops; if so, Moschops becomes a junior synonym
Avenantia kruuvleieusis is only moderately pachyostosed, with a narrow intertemporal region and large temporal fossa. Possibly this aooarently abarrent form may simply be a juvenile of Moschops.
Criocephalus vanderbyli Broom 1928b (= Criocephalus gunyankaensis?)Horizon: Lower Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
Comments: Criocephalus is known from at least half a dozen skulls are now known. The intertemporal region is very broad and the cranial roof greatly thickened by pachyostosis. Of the two named species, one C. vanderbyli, is South African and the other, C. gunyankaensis is Rhodesian. If these are contemporaries I have no doubt they would turn out to be synonyms. Boonstra 1963 considers this taxon the most specialised of the Moschopines.
This is tribe of medium-sized tapinocephalids includes a single species, Riebeeckosaurus longirostris. It is distinguished by a very long and slender snout and a narrow intertemporal region which forms a narrow sagittal crest, and moderate pachyostosis. Two skulls are known both from the Tapinocephalus Zone horizon.
Riebeeckosaurus longirostris Boonstra 1952bHorizon: Middle Tapinocephalus Zone, Karoo deposts, Lower Beaufort Beds; Beaufort West, South Africa
|some Links and References|
R.T.Bakker, "Dinosaur Renaissance", Scientific American April 1975
R. T. Bakker, 1986, The Dinosaur Heresies : New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction Wm. Morrow & Co.; New York., Reissue edition (August 1996) Ingrim
L. D. Boonstra, "The skull of Tapinocephalus and its near relatives" Annals of the South African Museum, 43 Part 3 pp. 137-169, 17 figs, plate 4.
L. D. Boonstra, 1965, "The skull of Struthiocephalus kitchingi". Annals of the South African Museum, 48 Part 14 pp. 251-265, 11 figs.
L. D. Boonstra, 1969, "The Fauna of the Tapinocephalus Zone (Beaufort Beds of the Karoo)", Annals of the South African Museum, 56 (1) pp. 1-73
Robert L. Carroll, 1988 Vertebrate Paleontology and Evolution, W.H. Freeman and Co., New York
Gregory, W.T., 1926, "The skeleton of Moschops capensis Broom, a dinocephalian reptile from the Permian of South Africa.", Bull. Amer. Mus. Nat. Hist. Volume 56, pp. 179-251 card
Karl Alfred von Zittel, 1932, Textbook of Paleontology, vol.II, MacMillan & Co. Limited, London, Vol. II, Edited and Translated by Charles R. Eastman, PhD. pp.254-256
Dinocephalia after Carroll 1988 - cladogram and genus list, based on Robert L. Carroll Vertebrate Paleontology and Evolution - Mikko K. Haaramo
Ulemosaurus svijagensis - same content as preceeding page, but different photo
Palaeos Page (incorporates some of this material, plus a lot of additional material)