Microsauria

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Microsauria
Temporal range: Late Carboniferous-Early Permian, 318.1–270.6Ma
Possible descendant taxon Lissamphibia survives to present
Microsauria.jpg
Microsauria diversity. (Hyloplesion (A), Pantylus (B), Pelodosotis (C) & Rhynchonkos (D))
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: "Amphibia" (wide sense)
Subclass: Lepospondyli
Order: "Microsauria"
Dawson, 1863

Microsauria ("small lizards") is an extinct order of lepospondyl amphibians from the late Carboniferous and early Permian periods. It is the most diverse and species-rich group of lepospondyls.[1][2] Recently, Microsauria has been considered paraphyletic, as several other non-microsaur lepospondyl groups such as Lysorophia seem to be nested in it.[1][3][4] Microsauria is now commonly used as a collective term for the grade of lepospondyls that were originally classified as members of Microsauria.[2]

The microsaurs all had short tails and small legs, but were otherwise quite varied in form. The group included lizard-like animals that were relatively well-adapted to living on dry land, burrowing forms, and others that, like the modern axolotl, retained their gills into adult life, and so presumably never left the water.[5]

They are possible ancestors of the newts and salamanders, if that group did not arise from the temnospondyls along with the frogs and toads.[5]

Distribution[edit]

Microsaurs are known from Europe and North America.

Microsaur remains have been found from Europe and North America in Late Carboniferous and Early Permian localities. Most North American microsaurs have been found in the United States in Arizona,[6] Texas, Oklahoma, Ohio,[7] Illinois, as well as Kansas and Nebraska,[8] although remains have also been found in Nova Scotia.[9] In Europe, microsaurs are known from Germany and the Czech Republic. Possible microsaur remains have also been found from strata in the town of Vyazniki in the Vladimir Oblast of Russia.[10] These strata are Late Permian in age, near the Permo-Triassic boundary. The microsaur material at Vyazniki may be the youngest record of microsaurs, and would extend their range by around 20 million years.

Classification[edit]

Cladogram modified from Anderson (2001):[3]

Lepospondyli 

Utaherpeton




Hyloplesion





Odonterpeton



 Hapsidopareiontidae 

Saxonerpeton




Hapsidopareion



Llistrofus





 Tuditanidae 

Asaphestera



Tuditanus




 Ostodolepidae 

Micraroter



Pelodosotis





 Pantylidae 

Pantylus




Stegotretus



Sparodus




 Gymnarthridae 

Cardiocephalus



Euryodus






Rhynchonkos




Eocaecilia (Lissamphibia)


 Brachystelechidae 

Batropetes




Carrolla



Quasicaecilia













Microbrachis




Adelospondyli




Scincosaurus



 Urocordylidae 

Sauropleura




Urocordylus




Ctenerpeton



Ptyonius






 Keraterpetontidae 


Batrachiderpeton



Keraterpeton





Diceratosaurus




Diploceraspis



Diplocaulus







Lysorophia



Aïstopoda










    Microsaurs

Cladogram from Ruta and Coates (2007):[4]

"Microsauria" 


Odonterpeton




Hyloplesion



Microbrachis






Brachystelechidae





Tuditanidae




Hapsidopareiontidae




Ostodolepidae




Rhynchonkos



Gymnarthridae








Pantylidae




Lysorophia




Nectridea



Aïstopoda








References[edit]

  1. ^ a b Ruta, M.; Coates, M.I.; and Quicke, D.L.J. (2003). "Early tetrapod relationships revisited". Biological Reviews 78 (2): 251–345. doi:10.1017/S1464793102006103. PMID 12803423. 
  2. ^ a b Bolt, J.R.; and Rieppel, O. (2009). "The holotype skull of Llistrofus pricei Carroll and Gaskill, 1978 (Microsauria: Hapsidopareiontidae)". Journal of Paleontology 83 (3): 471–483. doi:10.1666/08-076.1. 
  3. ^ a b Anderson, J.S. (2001). "The phylogenetic trunk: Maximal inclusion of taxa with missing data in an analysis of the Lepospondyli (Vertebrata, Tetrapoda)". Systematic Biology 50 (2): 170–193. doi:10.1080/10635150119889. PMID 12116927. 
  4. ^ a b Ruta, M.; and Coates, M.I. (2007). "Dates, nodes, and character conflict: addressing the lissamphibian origin problem". Journal of Systematic Palaeontology 5: 69–122. doi:10.1017/S1477201906002008. 
  5. ^ a b Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 55. ISBN 1-84028-152-9. 
  6. ^ Thayer, D.W. (1985). "New Pennsylvanian lepospondyl amphibians from the Swisshelm Mountains, Arizona". Journal of Paleontology 59 (3): 684–700. 
  7. ^ Hook, R. W.; and Baird, D. (1986). "The Diamond Coal Mine of Linton, Ohio, and its Pennsylvanian-Age vertebrates". Journal of Vertebrate Paleontology 6 (2): 174–190. doi:10.1080/02724634.1986.10011609. 
  8. ^ Huttenlocker, A. K.; Pardo, J. D.; Small, B. J.; Anderson, J. S. (2013). "Cranial morphology of recumbirostrans (Lepospondyli) from the Permian of Kansas and Nebraska, and early morphological evolution inferred by micro-computed tomography". Journal of Vertebrate Paleontology 33 (3): 540.
  9. ^ Steen, M.C. (1934). "The amphibian fauna from the South Joggins, Nova Scotia". Proceedings of the Zoological Society of London 104 (3): 465–504. doi:10.1111/j.1096-3642.1934.tb01644.x. 
  10. ^ Sennikov, A.G.; and Golubev, V.K. (2006). "Vyazniki biotic assemblage of the terminal Permian". Paleontological Journal 40 (Suppl. 4): S475–S481. doi:10.1134/S0031030106100078. 

External links[edit]