Kheper Home | Kheper Palaeo Home | Topics Index | New or updated | Search


link to palaeos com Kingdoms of Life > Wikipedia link Animalia > link to palaeos com Vertebrata > link to palaeos com Tetrapoda > link to palaeos com Theropsida > Therapsida


Author's note: these pages were written some years ago. I am not planning to update them. For a more current coverage, see the link to palaeos com Palaeos website (to which many links on these pages point to anyway. More info here


Therapsida

Cynognathus
Cynognathus - link to palaeos com early Triassic period

image from Illustrated Encyclopaedia of Dinosaurs and Prehistoric Animals, Barry.Cox, R.J.G.Savage, Brian Gardiner, Dougal Dixon, illustration by Steve Kirk)

The therapsids, also called mammal-like reptiles and paramammals, were advanced synapsid reptiles, and the direct ancestors of the mammals. The traditional Linnean classification groups the therapsids into several suborders - usually Phthinosuchia/Biarmosuchia, Dinocephalia, Anomodontia, and Theriodontia, this last often subdivided. A suggested cladistic tree is as follows:


<==Therapsida
   |--Tetraceratops
   `--+--Biarmosuchia
       |--Biarmosuchidae
       |?--"Phthinosuchidae"
       `-+-Eotitanosuchidae
          |   
          `--Eutherapsida
             |--Dinocephalia
             |  |--Anteosauria
             |  |  |--Stenocybidae
             |  |  `--Brithopodidae / Anteosauridae
             |  |?--Estemmenosuchidae
             |  `--Tapinocephalia
             |     |--Styracocephalidae
             |     `--+--Titanosuchidae
             |         `--Tapinocephalidae
             `--Neotherapsida
                |-+-Anomodontia
                | `-+-Galechiridae
                |    |--Otsheriidae
                |    `-+-Venjukoviidae
                |       `-+-Galeopsidae
                |          `-+-Dicynodontia
                |             `-+-Eodicynodontidae
                |                `-+-+-Endothiodonidae
                |                   |  `-+-Dicynodontoidea
                |                   |    `---Pristerodontoidea
                |                   |-+-Emydopoidea
                |                   |  `--Robertoidea
                |                   `--Kingoriidae
                 `--Theriodontia
                   |--Gorgonopsia
                   `--Eutheriodontia
                      |--Therocephalia
                      `--Cynodontia
                             `-+-Procyonsuchidae
                                `-+-Galesauridae
                                   `--Eucynodontia
                                       |--Cynognathidae
                                       `--Probainognathia
                                         |--Tritylodontoidea
                                         |  |--Diademodontidae
                                         |  |--Trirachodontidae
                                         |  |--Traversodontidae
                                         |  `--Tritylodontidae
                                         `--Chiniquodontoidea
                                            |-+-Chiniquodontidae
                                            |  `--Probainognathidae
                                            |--Tritheledontidae
                                            `--+?-Abelobasilus
                                                `--+?-Sinoconodon
                                                    |?-Gobiconodontidae
                                                    `--link to palaeos com Mammalia 

The above cladogram is taken from Jack Conrad's Vertebrate Paleontology site, along with modifications by Gillian King, The dicynodonts, A Study in palaeobiology, (Chapman & Hall, 199)), and Christian Kammerer (basal Anomodontia). Note that this phylogeny is not necessarily the only, or even the best, possible one.

A suggested phylogeny of the Therapsid groups is as follows: Evolving from mid-Permian ancestors like Tetraceratops (a small reptile completely unrelated to the well-known dinosaur Triceratops), these reptiles evolved progressively more mammalian features, first in the (to us because of lack of knowledge) disorderly branching of poorly known basal forms like the Biarmosuchia, Phthinosuchia, and Eotitanosuchia, from which developed a threefold branching. The earliest to develop were the somewhat more advanced but still ungainly carnivores, omnivores and herbivores of the Dinocephalian lineages, then following them the two very distinct lines of adaptive evolution, the diverse and succesful dicynodonts, and the the very mammal-like theriodonts. The latter group were to become the ancestors of link to palaeos com mammals, through the various intermediate stages suggested here.

These three principal subgroups are usually ranked as separate suborders - Dinocephalia, Anomodontia, and Theriodontia, although their diversity is such that I for one would not be upset as a bit of taxonomic inflation that would raise them to ordinal rank. As with so much in nature, it seems to all be about food, at least getting enough food, and processing it better. Quite simply, the three principal radiations within the Therapsida appear to be based on three solutions to the problem of bringing the food-processing surfaces of the upper and lower jaws into closer contact in order to achieve a more efficient system than existed in the sphenacodontids for subdividing both plant and animal foodstuffs.

evolution of the Therapsids exclusive of the cynodonts

diagram from James A. Hopson, "The Origin and Adaptive Radiation of Mammal-Like Reptiles and Non-Therian Mammals, Annals of the New York Academy of Sciences 167:199-216, 1969

Unlike the pelycosaurs, which are known mainly from the link to palaeos com early Permian of North America (with a smattering of European forms), but this is due to accidents of preservation in the fossil record, and possibly also restruction to the equatorial belt during the bitter Permo-Carboniferous ice ages), our knowledge regarding the therapsids is more extensive. Members of all the basic Therapsid lineages apart from the Theriodonta occur in the earliest therapsid fauna of Russia, the early Middle Permian Ocher fauna (Wordian Epoch). It use dto be thought that even more primitive fragmentary remains from the slightly earlier San Angelo formation of Texas also were of this category (Olson, 1962), but it is now known that these were falsely identified - they were actually Caseid peycosaurs, not therapsids at all.

The fossil remains of these animals are also represented in the middle and upper Permian deposits of Africa, especially the spectacular Karroo formation of South Africa, and from other formations in Russia, and the uppermost Permian sediments of China, and the link to palaeos com Triassic of those three countries (especially South Africa) plus also South America, with rarer specimens from Europe, North America, Australia, and Antarctica. Only the Tritylodontids survived into the link to palaeos com Jurassic, and are known from Europe and China.



some printed references some Links and References Web links

Great Russian Dino Expo siteSynapsids - short overview of mammal-like reptiles, with emphasis on Russian forms.  Includes an evolution diagram


FAQs - Mammal-like reptiles - Answers to school children's questions about the world and lives of a range of ancient reptiles that gave rise to the mammals.

Barren Karoo's fossil treasure house - very readable on-line article

The real prehistoric stars - the Therapsida of the Karoo basin and elsewhere

web pageoriginal drawingcladogramTherapsida - by Jack Conrad - includes an up to date Cladogram, essay, and technical diagnosis of the group

Palaeos link to palaeos com Therapsida Vertebrate notes - dense bu excellent technical definition

cladogramTherapsida - cladogram and short bibliography - Mikko K. Haaramo

web pageartworkcladogram Synapsida - Mammals and their kin - T. Mike Casey - cladogram covers both Pelycosaurs and Therapsids

printed referenceCarroll, R. L. Vertebrate paleontology and evolution. -W. H. Freeman and company, New York, 1988

printed referenceEdwin H. Colbert, Evolution of the Vertebrates, 2nd edition, 1969, John Wiley & Sons

printed referenceJames A. Hopson, "The Origin and Adaptive Radiation of Mammal-Like Reptiles and Non-Therian Mammals, Annals of the New York Academy of Sciences 167:199-216, 1969

printed referenceJames A. Hopson and Herbert R. Barghusen, "An Analysis of Therapsid Relationships", in The Ecology and Biology of Mammal-Like Reptiles ed. by Nocholas Hotton III, Paul D. MacLean, Jan J. Roth and E. Carol Roth, Smithsonian Institute Press, Washington and London, 1986, pp.83-106



link to palaeos com Palaeos link to palaeos com Palaeos Page (incorporates some of this material, plus a lot of additional material)




Kheper index page
Palaeo index page
Therapsida main page

link to palaeos com Kingdoms of Life > Wikipedia link Animalia > link to palaeos com Vertebrata > link to palaeos com Tetrapoda > link to palaeos com Theropsida > Therapsida


Kheper Home | Kheper Palaeo Home | Topics Index | New or updated | Search


Creative Commons License
Unless otherwise attributed or quoted, all text is licensed under
the Creative Commons License 1.0 and a 2.0. This licence does not cover quoted material, and images, which are copyright their respective owners.

images not loading? | error messages? | broken links? | suggestions? | criticism?
contact me

page by M.Alan Kazlev
page uploaded 10 November 1999. Reposted and last modified 1 September 2005, links updated 16 January 2010