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 Lower Carboniferous to the lowermost Upper Permian. The most derived clade within the holospondyls is the Aistopoda, legless eel-like forms. Inclusion of the aistopods within the lepospondyls (the parent clade of the holospondyls) is rendered potentially problematic by their relatively early appearance (Visean) in the fossil record compared to other lepospondyls (Serpukhovian), despite their seemingly relatively derived position.

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]
    |--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
       |    `--+--Urocordylus wandesfordii Wright & Huxley 1866 AR08, RCQ03
       |       `--+--Ptyonius marshii Cope 1875 AR08, RCQ03
       |          `--Ctenerpeton Cope 1897 RCQ03
       |               `--C. alveolatum RCQ03
       `--+--Diplocaulidae RCQ03
          |    |--+--Keraterpeton [Keraterpetontidae] AR08
          |    |  |    `--K. galvani Wright & Huxley 1866 RCQ03
          |    |  `--Batrachiderpeton reticulatum (Hancock & Atthey 1869) AR08, RCQ03
          |    `--+--Diceratosaurus brevirostris (Cope 1875) AR08, RCQ03
          |       `--+--Diploceraspis burkei Romer 1952 AR08, RCQ03
          |          `--Diplocaulus AR08
          |               |--D. magnicornis Cope 1882 RCQ03
          |               `--D. primus RCQ03
          `--+--Lysorophia RCQ03
             |    |--Lysorophus [Lysorophidae] PS88
             |    `--Brachydectes [Cocytinidae] AR08
             |         |--B. elongatus Wellstead 1991 RCQ03
             |         `--B. newberryi Cope 1868 RCQ03
             `--Aistopoda ACR03
                  |--Lethiscus Wellstead 1982 [Lethiscidae] ACR03
                  |    `--L. stocki Wellstead 1982 ACR03
                  `--+--Ophiderpeton Wright & Huxley 1866 ACR03, A03 [Ophiderpetontidae]
                     |    |--*O. brownriggi Wright & Huxley 1866 A03, ACR03
                     |    |--O. kirktonense Milner 1994 ACR03
                     |    `--O. swisshelmense Thayer 1985 ACR03
                     `--+--Oestocephalidae ACR03
                        |    |--Coloraderpeton Vaughn 1969 ACR03, A03
                        |    |    `--*C. brilli Vaughn 1969 A03, ACR03
                        |    `--Oestocephalus Cope 1868 A03
                        |         |--*O. amphiuminum (Cope 1868) ACR03 (see below for synonymy)
                        |         `--O. nanum (Hancock & Atthey 1868) ACR03 [=Ophiderpeton nanum A03]
                        `--Phlegethontioidea ACR03
                             |--Pseudophlegethontia Anderson 2003 [Pseudophlegethontiidae] ACR03
                             |    `--P. turnbullorum Anderson 2003 ACR03
                             `--Phlegethontiidae ACR03
                                  |--Sillerpeton permianum Lund 1978 ACR03
                                  `--Phlegethontia ACR03
                                       |--P. linearis Cope 1871 ACR03
                                       |--P. longissima (Fritsch 1875) ACR03
                                       `--P. phanerhapha Thayer 1985 ACR03

*Oestocephalus amphiuminum (Cope 1868) ACR03 [incl. Thyrsidium fasciculare Cope 1875 A03, Ophiderpeton granulosum Fritsch 1879 A03, Cercariomorphus parvisquamis Cope 1885 A03, Op. pectinatum Fritsch 1879 A03, Oestocephalus remex Cope 1869 A03, Ophiderpeton vicinum Fritsch 1879 A03, Op. zieglerianum Fritsch 1879 A03]

*Type species of generic name indicated


[A03] Anderson, J. S. 2003. Cranial anatomy of Coloraderpeton brilli, postcranial anatomy of Oestocephalus amphiuminus, and reconsideration of Ophiderpetontidae (Tetrapoda: Lepospondyli: Aistopoda). Journal of Vertebrate Paleontology 23 (3): 532-543.

[ACR03] Anderson, J. S., R. L. Carroll & T. B. Rowe. 2003. New information on Lethiscus stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda. Canadian Journal of Earth Sciences 40: 1071-1083.

[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.

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

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