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SYNAPSIDA | THERAPSIDA |--Biarmosuchia `--+--Dinocephalia | |--Anteosauria | `--Tapinocephalia | |--Styracocephalus | `--+--Titanosuchidae | | |--Titanosuchus | | `--Jonkeria | `--Tapinocephalidae `--+--Anomodontia | |--Venyukovioidea | `--Dicynodontia `--Theriodontia |--Gorgonopsia `--+--Therocephalia `--CYNODONTIA
The Tapinocephalia are the major herbivorous clade of the Dinocephalia. Unlike the anteosaurs and estemmenosuchids, the tapinocephalians are primarily an African group. The estemmenosuchids and pareiasaurs may have occupied this paleo-bovine niche in the north. Only one tapinocephalian, Ulemosaurus, is known from Russia. The Tapinocephalia are thought to consist of three clades: Styracocephalus (sometimes assigned to a family of its own, the Styracocephalidae), the Titanosuchidae, and the very successful Tapinocephalidae. ATW020524.
A number of rather imperfect skulls constitute the Styracocephalidae, small herbivorous dinocephalians who retained a moderate canine. Characteristic are the prominent posteriorly directed tabular bosses, weak, conical incisors and canine, and a long series of postcanines. The palatal teeth are very well developed, even on the vomer. All known forms come from a single species, Styracocephalus platyrhynchus Haughton 1929, from the Tapinocephalus Zone, Beaufort Beds, Beaufort West, Karoo, South Africa. These animals are similar to both the anteosaurs and the Estemmenosuchids, and are indeed believed to be closely related to both. MAK000809.
Among the Titanosuchidae, the large canine has been retained and the very strong incisors have a piercing talon and a crushing heel. Although the sharp front incisors and fanglike canines at the front of the jaws, might seem to indicate a carnivorous diet, the long series of post-canine teeth have leaf-shaped and serrated spatulate crowns, indicating these animals were at least partially herbivorous. Titanosuchids share with the more specialized tapinocephalids the presence of an enlarged heel on the incisor teeth, with a reduced canine, with the jaw hinge still further anterior. There is however very little pachyostosis (thickening of the skull).
There are only two genera, distinguished only by length of limb bones. It is sometimes suggested that the short-limbed Jonkeria was a herbivore, and the longer limbed Titanosuchus a carnivore. Boonstra (1969) has the family Titanosuchidae composed of two genera and nine species. I think this many species is excessive, it was probably no more than three or four species. Boonstra also states that the genera Titanosuchus and Jonkeria cannot be distinguished from one another on either cranial or dental characters, but in Titanosuchus the limb-bones are long, whereas in all the species of Jonkeria they are short and squat. However, King (1988) suggests a number of differences, including a large and massive skull in Titanosuchus, and a medium to large skull in Jonkeria, indicating Titanosuchus's supposedly carnivorous lifestyle in contrast to the presumably herbivorous Jonkeria More probably both were omnivores, eating mostly plants, but sometimes carrion or even live animals (comparable omnivores today include bears, pigs, and baboons). MAK000802.
Tapinocephalia: Tapinocephalia > Anteosaurus. Criocephalus.
Range: Middle Permian to Late Permian of Russia & South Africa
Phylogeny: Dinocephalia : Anteosauria + * : Styracocephalus + (Titanosuchidae + Tapinocephalidae).
Characters: various horns & cranial protuberances [RS01]; pachyostosis of skull bones (head butting?) [RS01]; most have upper & lower canines [RS01]; incisors, even postcanine dentition may be interdigitating and equipped with heel & talon [RS01].
References: Rubidge & Sidor (2001) [RS01]
Note: My personal candidate for ugliest tetrapod taxon of all time. ATW040312.
Range: Middle Permian of South Africa (Tapinocephalus Zone).
Phylogeny: Tapinocephalia : (Titanosuchidae + Tapinocephalidae) + *.
Characters: prominent posteriorly directed tabular bosses; palatal teeth very well developed, even on vomer; weak, conical incisors and canine; long series of postcanines.
Note: Note that all three dinocephalian clades developed similar dentition independently. Styracocephalus, like the most basal therapsids, had numerous palatal teeth and relatively undeveloped incisors. Yet, as we will see, the advanced tapinocephalids, like the more derived anteosaurs and estemmenosuchids, increasing relied on powerful interdigitating incisors, with a very reduced complement of palatal teeth and relatively weak postcanines. ATW020524.
Range: Middle Permian of South Africa.
Phylogeny: Tapinocephalia :: Tapinocephalidae + * : Titanosuchus + Jonkeria.
Characters: pachyostosis less pronounced than in tapinocephalids; jaw hinge further anterior than in tapinocephalids; incisors strong, with talon and a crushing heel; canines large; numerous postcanine teeth with leaf-shaped & serrated spatulate crowns. ATW020524.
Note: As is so often the case, the understanding of this group has been cluttered by a terrible excess of useless names, described on the basis of fragmentary material, and giving the impression that there were many more species around than there really were. The problems began when Sir Richard Owen, the famous English paleontologist, described Titanosuchus ferox in 1879 based on the roots of an incomplete set of teeth. As all the material from the Karoo was new to science at the time, even the poorest specimen warranted description.
In the race to name as many new species as possible Broom added a ballast of names on equally poor material. It has since been shown that even well-preserved batteries of teeth exhibit so much variation, with even the left and right sides of the same skull, that dental features are a very unreliable criterion for distinguishing between titanosuchids. MAK000802
Titanosuchus: (= Scapanodon = Parascapanodon) T. ferox Owen 1879.
Range: Middle Permian of South Africa (Tapinocephalus Zone).
Phylogeny: Titanosuchidae : Jonkeria + *.
Characters: 2.5 m; legs short.
Links: South African Museum - Fossil Reptiles of the South African Karoo; Dinosaurios: Titanosuchus; Titanosuchus.
Note: Widely said to be a carnivore, but apparently this is incorrect. ATW020524.
Jonkeria: (= Phoneosuchus angusticeps) J. truculenta Van Hoepen 1916b.
Range: Middle(?) Permian of South Africa.
Phylogeny: Titanosuchidae : Titanosuchus + *.
Characters: Very large (4-5 m); elongated snout; large incisors and long canines; limbs stout & long. ATW020524.
J. ingens Broom 1929. The holotype, originally Dinophoneus ingens, together with its synonym, J. pugnax Broom, 1929, and three other known skulls constitute a distinct species of Jonkeria.
J. vanderbyli Broom, 1929: The holotype is a good skull of Jonkeria which according to Boonstra is easily distinguishable from the other species of the genus.
J. haughtoni Broom, 1929: The type is a fairly good skull, with some limb-bones, which can be placed in the genus Jonkeria. It can be distinguished from the other species of the genus. Synonym: Dinosphageus haughtoni Broom, 1929 - original name J. crassus Broom, 1929. According to Boonstra, in the holotype consisting of dentaries and postcranial bones, the humerus cannot be distinguished from that of J. haughtoni, and as there are no other distinctive features it should be considered a synonym of J. haughtoni.
J. koupensis Boonstra, 1955: The holotype is a good pelvis readily distinguishable from that of any other known species of Jonkeria.
J. parva Boonstra, 1955: A small humerus is quite distinct from that of the other known species of Jonkeria. I think it is not unlikely this may turn out to a distorted or otherwise modified specimen.
J. rossouwi Boonstra, 1955: The holotype consists of postcranial bones readily distinguishable from those of the other species of the genus. Two other specimens are known that show the same distinctive features, indicating this is a valid type (probably corresponding to one of the species name on skull characteristics).
J. boonstrai Janensch, 1959: According to Boonstra, Janensch has given a convincing diagnosis of the specific features of the holotype skull. He also stresses the herbivorous nature of the dentition. MAK000809.
References: Boonstra (1969).
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