Alternative illustrations of the skeleton of Keraterpeton galvani by William Baily (left) and Joseph Dinkel (right).

Belongs within: Lepospondyli.

The Holospondyli are a clade of aquatic amphibian-grade tetrapods found from the middle Carboniferous to the lowermost Upper Permian. Two generally recognised groups, the Nectridea and Lysorophia, are likely members of this clade though the 'Nectridea' may not be monophyletic; a third group, the Aistopoda, has also been suggested as related to nectrideans in the past. The 'Nectridea' are a diverse group united by features of the post-cranial anatomy such as a remarkably elongate tail. Well-known exemplars include the boomerang-headed Diplocaulus. The Lysorophia are small, serpentine animals with an extremely elongate trunk and reduced, poorly ossified limbs and girdles (Ruta et al. 2003).

Synapomorphies (from Ruta et al. 2003): Prefrontal less than three times as long as wide; ectopterygoid with tooth row, lacking denticles; most trunk ribs lacking elongate posterodorsal flange; extra articulations present above zygapophyses in at least some trunk and caudal vertebrae; neural and haemal spines rectangular to fan-shaped in lateral view, facing each other dorsoventrally; haemal spines fused to caudal centra; neural spines of trunk vertebrae fused to centra; capitular facets absent on posterior rim of vertebral midtrunk centra.

<==Holospondyli [Nectridea]
    |  i. s.: Arizonerpeton Thayer 1985 T85
    |           `--*A. wellsi Thayer 1985 T85
    |--Scincosaurus [Scincosauridae] AR08
    |    `--S. crassus Fritsch 1876 RCQ03
    `--+--Urocordylidae RCQ03
       |    |--Sauropleura Cope 1868 AR08, RCQ03
       |    |    |--S. scalaris (Fritsch 1883) RCQ03
       |    |    `--+--S. bairdi RCQ03
       |    |       `--S. pectinata Cope 1868 RCQ03
       |    `--Urocordylinae T85
       |         |--Urocordylus AR08
       |         |    |--U. scalaris F04
       |         |    `--U. wandesfordii Wright & Huxley 1866 RCQ03
       |         `--+--Ctenerpeton Cope 1897 RCQ03
       |            |    `--C. alveolatum RCQ03
       |            `--Ptyonius Cope 1874 AR08, T85
       |                 |--P. marshii Cope 1875 RCQ03
       |                 `--P. olisthmonaias Thayer 1985 T85
       `--+--Diplocaulidae RCQ03
          |    |--+--Batrachiderpeton reticulatum (Hancock & Atthey 1869) AR08, RCQ03
          |    |  `--Keraterpeton [Keraterpetontidae] AR08
          |    |       `--K. galvani Wright & Huxley 1866 RCQ03
          |    `--+--Diceratosaurus brevirostris (Cope 1875) AR08, RCQ03
          |       `--+--Diploceraspis burkei Romer 1952 AR08, RCQ03
          |          `--Diplocaulus Cope 1882 AR08, D07
          |               |--D. magnicornis Cope 1882 RCQ03
          |               |--D. primus RCQ03
          |               `--D. salamandroides C07
          `--Lysorophia RCQ03
               |--Lysorophus [Lysorophidae] PS88
               |    `--L. tricarinatus C07
               |--Molgophidae G88
               |    |--Molgophis G88
               |    `--Megamolgophis G88
               `--Cocytinidae AR08
                    |--Cocytinus G88
                    `--Brachydectes AR08
                         |--B. elongatus Wellstead 1991 RCQ03
                         `--B. newberryi Cope 1868 RCQ03

*Type species of generic name indicated


[AR08] Anderson, J. S., R. R. Reisz, D. Scott, N. B. Fröbisch & S. S. Sumida. 2008. A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders. Nature 453: 515–518.

[C07] Case, E. C. 1907. Revision of the Pelycosauria of North America. Carnegie Institute of Washington Publication 55: 1–176, 35 pls.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[F04] Fritsch, A. 1904. Palaeozoische Arachniden. Selestverlag: Prague.

[G88] Gray, J. 1988. Evolution of the freshwater ecosystem: the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology 62: 1–214.

[PS88] Panchen, A. L., & T. R. Smithson. 1988. The relationships of the earliest tetrapods. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 1. Amphibians, Reptiles, Birds pp. 1–32. Clarendon Press: Oxford.

[RCQ03] Ruta, M., M. I. Coates & D. L. J. Quicke. 2003. Early tetrapod relationships revisited. Biological Reviews 78: 251–345.

[T85] Thayer, D. W. 1985. New Pennsylvanian lepospondyl amphibians from the Swisshelm Mountains, Arizona. Journal of Paleontology 59 (3): 684–700.

Last updated: 27 August 2018.

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