Dissorophidae

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Dissorophidae
Temporal range: Late Carboniferous - Middle Permian, 301–270 Ma
Cacops Field Museum.jpg
Skeleton of Cacops in the Field Museum
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Order: Temnospondyli
Clade: Olsoniformes
Family: Dissorophidae
Boulenger, 1902
Subgroups

See text.

Synonyms
  • Platyhystrigidae
  • Aspidosauridae
  • Conjunctiidae
  • Cacopidae

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, Colorado, and New Mexico, the armor developed into a sort of ridge or sail.

Not all Dissorophids were squat-bodied big headed animals. Nooxobeia, 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),[1] as it is closely related to another family called Amphibamidae that is often considered ancestral to this group,[2] although it could also be on the tetrapod stem.[3]

Fossil range[edit]

Below is a timeline of the known fossil ranges of dissorophids.[4]

Paleozoic EraPermianCarboniferousZygosaurusKamacopsIratusaurusAnakamacopsNoxoobeiaCacopsCacopsDissorophusBroiliellusAspidosaurusAspidosaurusBroiliellusConjunctioDissorophusBroiliellusConjunctioBrevidorsumAspidosaurusAspidosaurusPlatyhystrixAspidosaurusPlatyhystrixAstreptorhachisPaleozoic EraPermianCarboniferous

Phylogeny[edit]

Below is a cladogram from Schoch (2012):[5]


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[edit]

  1. ^ Schoch, R.R. (2018) The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls. Journal of Paleontology. Online edition. doi:10.1017/jpa.2018.67.
  2. ^ 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
  3. ^ 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.
  4. ^ 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.
  5. ^ Schoch, R. R. (2012). "Character distribution and phylogeny of the dissorophid temnospondyls". Fossil Record. 15 (2): 121–137. doi:10.1002/mmng.201200010.