Ecology | Paleontology | Timescale | Paleozoic
For some unknown reason, all of the large herbivore families of the Dinocephalian Empire (Dynasty II - A-E in Fig.2), with the exception of the semi-aquatic pareiasaurs ), and corresponding very large predators (anteosaurids, A in Fig. 2), and the two most common and diverse medium-to-large carnivore families (D and E in Fig. 2) disappear abruptly together in the fossil record of the Karroo Basin in South Africa. This apparently massive extinction marks the division between the Tapinocephalus Zone and the Kistecephalus Zone in the Karroo, and between the Dinocephalian Empire (= Bakker's Dynasty II) and the Endothiodon-Dicynodont Empire (=Bakker's Dynasty III). It is not known if similiar mass-extinctions occured eslewhere, as the fossil record is patchy in its distribution, but later deposits from Russia and China show plenty of Endothiodon-Dicynodont forms, but not a single Dinocephalian.
Temnospondyl amphibian piscivore); Procynosuchus (Procynosuchidae - cynodont therapsid carnivore/piscivore/insectivore); Pareiasaurus (Pareiasauridae - Anapsid herbivore); Paliguana ("Paliguanidae" - diapsid/"eosuchian" insectivore); Aulacephalodon (Aulacephalodontidae - dicynodont therapsid herbivore); Gorgonops (Gorgonopsidae therapsid carnivore);
In the earliest known post-Tapinocephalus Zone fauna of southern Africa (where the fossil record for late Permian tetrapods is most complete), new groups of big herbivores - the beaked and toothless dicynodonts - appear. These were clearly descended from those genera which were common but restricted to small body sizes during the Tapinocephalus Zone. Initial diversity of large dicynodonts may have been low, with one genus, Endothiodon, dominating some early local faunas. But within a relatively short period more big dicynodont families were added, and at the acme of Endothiodon-Dicynodont Empire (faunal stages 4 and 5 in Fig. 2) four fully terrestrial big families are common, plus pareiasaurs, the big aquatic herbivores that were the only survivors over 15 kg from the Dinocephalian empire. Biomass D rises during this period, and appears to reach maximum in the Capitanian age, some time before end of the Endothiodon-Dicynodont Empire. In the latest fauna (late Daptocephalus zone, Wuchiapingian age, stage 5 in Fig. 2) one genus, Daptocephalus, increases in relative frequency at the expense of the other big herbivores; thus local diversity, measured by D, decreases although all of the genera and families seem to be present right through to the end of the zone.
Only one family dominates the top predator role, the gorgonopsians, making up nearly all the specimens known (C in Fig. 2). Large gorgonopsids were present but very rare in the preceding Tapinocephalus Zone (Dinocephalian empire). The medium-size hipposaurids, also present in the Tapinocephalus Zone, were wide-spread but uncommon. Towards the end of this period, two more large predator families appear - the proterosuchian thecodonts (archosaurs) and the therapsid moschorhinids (therocephalians). The latter make up about half the predator specimens in the latest Daptocephalus Zone faunas (late Wuchiapingian-early Changshingian).
Some time during the Changshingian age, the Endothiodon-Dicynodont empire is replaced by the Lystrosaur empire. In some instances Lystrosaurus and typically Dicynodon age animals opccur together, showing that this might be less a sudden mass extuinction and more a gradual transition. It is possible that the Lystrosaurus biota was better adapted to the increasingly arid climates of the end Permain
The following map by Anderson and Cruikshank give the known distribution of Endothiodon and Dicynodon age faunas. This refers only to the location of fossil remains. The actual distribution would naturally have been much wider.
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some Links and References |  |
J. M. Anderson & A. R. I. Cruikshank, "The Biostratigraphy of the Permian and Triassic, Part 5, a review of the classification and distribution of Permo-Triassic Tetrapods," in Paleontologica Africana, 21, 15-44 (1978)
R.T. Bakker, 1977 "Tetrapod Mass Extinctions - A model of the regulation of speciation rates and immigration by cycles of topographic diversity" in A. Hallam, ed. Patterns of Evolution as illustrated by the Fossil Record, Elsevier Scientific Publishing Company, Amsterdam, Oxford, New York, pp.439-68
Robert T. Bakker, "The Need for Endothermic Archosaurs", in R.D.K.Thomas and E.C.Olson, eds, A Cold
Look at the Warm Blooded Dinosaurs, AAAS Selected Symposium 28, p.366
Michael A. Cluver, 1978, Fossil Reptiles of the South African Karoo, South African Museum, Cape Town
Professor Paul Eric Olsen, Tetrapods
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Temnospondyli | Anapsida | Therapsida