Dissorophidae

Dissorophidae Temporal range: Late Carboniferous - Middle Permian, 304–268 Ma PreЄ Є O S D C P T J K Pg N
Skeleton of Cacops in the Field Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Temnospondyli
Clade:	†Olsoniformes
Family:	†Dissorophidae Boulenger, 1902
Subgroups
See text.

Dissorophidae is an extinct family of medium-sized, temnospondyl amphibians that flourished during the Late Pennsylvanian and early Permian periods in what is now North America and Europe. Despite being amphibians, they seem to be well developed for life on land, with well-developed limbs, solid vertebrae, and a row of armour plates of dermal bone, which both protected the animal and further strengthened the backbone.

A well known genus is Cacops, a squat solid animal from the late Early Permian (Artinskian age) Clear Fork group of Texas, with a relatively huge head, and a row of armor plates along the back. In the similar but slightly larger and more specialised genus, Platyhystrix, whose fossil remains are known from the Cutler Group of Utah, Coloardo, and New Mexico, the armor developed into a sort of ridge or sail.

Not all Dissorophids were squat-bodied big headed animals. Fayella, from the late Artinskian of Oklahoma, was lightly built with long limbs, obviously relying on speed rather than armour plating as a defense against predators.

There are a number of related forms which seem to have been more aquatic, which are known from the Late Permian of Russia and the Early Triassic of Gondwana.

It has been suggested that the Dissorophidae may be close to the ancestry of modern amphibians (Lissamphibia), as it is closely related to another family called Amphibamidae that is often considered ancestral to this group,^[1] although it could also be on the tetrapod stem.^[2]

Fossil range

Below is a timeline of the known fossil ranges of dissorophids.^[3]

Phylogeny

Below is a cladogram from Schoch (2012):^[4]

Dissorophoidea

Micromelerpetontidae Micromelerpeton Amphibamidae Platyrhinops Doleserpeton Olsoniformes Trematopidae Ecolsonia Fedexia Tambachia Anconastes Phonerpeton Acheloma Dissorophidae Platyhystrix Aspidosaurus Conjunctio Dissorophinae Dissorophus Broiliellus texensis Broiliellus brevis Broiliellus olsoni Eucacopinae Brevidorsum Admiral taxon Rio Arriba taxon Cacops morrisi Cacops aspidephorus Kamacops Zygosaurus

References

1. Ruta M, Coates MI. 2007. Dates, nodes and character conflict: addressing the lissamphibian origin problem. Journal of Systematic Palaeontology 5: 69-122. doi:10.1017/S1477201906002008
2. Marjanović, D; Laurin, M (2013). "The origin(s) of extant amphibians: a review with emphasis on the "lepospondyl hypothesis"". Geodiversitas 35: 207–272. doi:10.5252/g2013n1a8.
3. May, W.; Huttenlocker, A.K.; Pardoc, J.D.; Bencab, J.; Small, B.J. (2011). "New Upper Pennsylvanian armored dissorophid records (Temnospondyli, Dissorophoidea) from the U.S. midcontinent and the stratigraphic distributions of dissorophids". Journal of Vertebrate Paleontology 31 (4): 907–912. doi:10.1080/02724634.2011.582532.
4. Schoch, R. R. (2012). "Character distribution and phylogeny of the dissorophid temnospondyls". Fossil Record 15 (2): 121–137. doi:10.1002/mmng.201200010.

• Anderson, J. M.; Cruikshank, A. R. I. (1978). "The Biostratigraphy of the Permian and Triassic, Part 5, a review of the classification and distribution of Permo-Triassic Tetrapods". Paleontol. Afr. 21: 15–44.
• Benton, M. J. (1993) The Fossil Record 2. Chapman & Hall, London, 845 pp.
• Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
• Reisz, Robert, (no date), Biology 356 - Major Features of Vertebrate Evolution - The Origin of Tetrapods and Temnospondyls