Lepidosauria

Lower jaw of Lamiasaurus ferox, from Longrich et al. (2012).

Belongs within: Lepidosauromorpha.
Contains: Sphenodontia, Amphiglossus, Gekkota, Iguania, Lacertoidea, Anguimorpha, Scincidae, Cordylidae, Xantusiidae.

The clade Lepidosauria includes the Squamata (lizards and snakes) plus the Rhynchocephalia (tuatara). The earliest known possible lepidosaur is Palacrodon from the Lower Triassic of South Africa, with more definite lepidosaurs known from the Upper Triassic (Evans 1988). Of the two lineages within the Lepidosauria, the Rhynchocephalia are united by the presence of an enlarged palatine tooth row, roughly parallel to the maxilla, and by having the posterior process of the dentary extending beyond the coronoid. The basal rhynchocephalian Gephyrosaurus bridensis from the Early Jurassic of Wales has a pleurodont dentition (teeth fused to the inner surface of the jaw bone), in contrast to the acrodont dentition (teeth entirely fused to the jaw) of most Sphenodontia.

The Squamata, including snakes and lizards, are supported by a number of synapomorphies, including reduction or loss of the vomerine teeth and loss of the dermal gastralia (Evans 1988). Past authors have divided the Squamata between the fleshy-tongued Iguania and the Scleroglossa, in which the tongue is non-fleshy and the jaws alone are used to manipulate food. However, more recent phylogenetic analyses (primarily molecular) have indicated that the Iguania are not the sister taxon to the remaining squamates. A likely candidate for that position is the Dibamidae, a small family of legless lizards found in Mexico (Anelytropsis) and southeast Asia (Dibamus), with the Gekkota (geckoes) the next to diverge. Fossil squamates include Lamiasaurus ferox, a possible stem iguanian known from a jaw from the Late Cretaceous of Wyoming bearing widely spaced teeth that are constricted above the base, giving them the overall shape of a 'rifle cartridge or wine bottle' (Longrich et al. 2012).

Synapomorphies (from Evans 1988): Slender stapes; lacrimal restricted to orbit; teeth attached superficially to jaws; abducens canals complete, dorsum sellae well developed; caudal autotomy possible); acessory facets (zygosphene/zygantrum) on neural arches; first and fifth metacarpals shorter than second and fourth; third metacarpal longer than fourth metacarpal; ossified epiphyses with discrete centres; ilium with strong pubic flange; astragalus and calcaneum fuse in juvenile; lateral pes centrale fused to astragalus; loss of first distal tarsal; first metatarsal meeting astragalocalcaneum; loss or fusion of fifth distal tarsal; fifth metatarsal hooked in two planes; no perforating foramen in ankle.

Lepidosauria
    |--Rhynchocephalia [Sphenodontida] MH11
    |    |  i. s.: Palacrodon E88
    |    |         Polysphenodon E88
    |    |         Pelecymala E88
    |    |--Gephyrosaurus bridensis Evans 1980 Sa05
    |    `--Sphenodontia Sa05
    `--Squamata [Ascalabota, Autarchoglossa, Scleroglossa, Typhlophthalmi] MH11
         |  i. s.: Mimeosaurus RFN02
         |         Nucras E01
         |         Moanasaurus [incl. Rikisaurus] WH02
         |           |--‘Mosasaurus’ flemingi WH02
         |           |--M. mangahouangae WH02
         |           `--‘Rikisaurus’ tehoensis WH02
         |         Haasiasaurus [=Haasia] Sc05
         |           `--H. gittelmani [=Haasia gittelmani] Sc05
         |         Amblyrhynchus cristatus CH97
         |         Timon lepidus N10
         |         Aporosaura anchietae BH10
         |         Constrictor constrictor U57
         |         Takydromus smaragdinus MH11
         |         Amphiglossus MH11
         |         Brachymeles MH11
         |           |--B. gracilis MH11
         |           `--B. talinis MH11
         |         Pygomeles braconnieri MH11
         |         Neoseps reynoldsi MH11
         |         Scincopus fasciatus MH11
         |         Sphenops MH11
         |           |--S. boulengeri MH11
         |           `--S. sphenopsiformis MH11
         |         Sepsina angolensis MH11
         |         Platysaurus rhodesianus MH11
         |         Pseudocordylus microlepidotus MH11
         |         Mesaspis moreleti MH11
         |         Sauresia agasepsoides MH11
         |         Wetmorena haetiana MH11
         |         Gambelia wislizenii MH11
         |         Meroles cuneirostris MH11
         |         Tracheloptychus madagascariensis MH11
         |         Angolossaurus skoogi MH11
         |         Chaemasaura anguina MH11
         |         Cordylosaurus trivittata MH11
         |         Hyphalosaurus Gao, Tang & Wang 1999 D07
         |           `--H. lingyuanensis D07
         |         Monjurosuchus Endo 1940 D07
         |           `--M. splendens D07
         |         Stilosoma extenuatum F15
         |--Dibamidae [Dibamia] MH11
         |    |--Anelytropsis [Anelytropsidae] Sc05
         |    `--Dibamus novaeguineae MH11
         `--+--Gekkota MH11
            `--+--+--Iguania LBG12
               |  `--Lamiasaurus Longrich, Bhullar & Gauthier 2012 LBG12
               |       `--*L. ferox Longrich, Bhullar & Gauthier 2012 LBG12
               `--+--Lacertoidea LBG12
                  `--+--Anguimorpha LBG12
                     `--Scincomorpha [Scincoidea] LBG12
                          |  i. s.: Estescincosaurus cooki LBG12
                          |         Lonchisaurus Longrich, Bhullar & Gauthier 2012 LBG12
                          |           `--*L. trichurus Longrich, Bhullar & Gauthier 2012 LBG12
                          |         Aoncodromeus LBG12
                          |         Penemabuya LBG12
                          |         Othrioscincus LBG12
                          |         Palaeoscincosaurus LBG12
                          |         Palaeoxantusia LBG12
                          |--+--Scincidae MH11
                          |  `--Contogenys [Globauridae] LBG12
                          |       `--C. sloani LBG12
                          `--+--+--+--Meyasaurus MH11
                             |  |  `--Eolacerta MH11
                             |  `--+--Cordylidae MH11
                             |     `--+--Sakurasaurus MH11
                             |        `--Ornatocephalus MH11
                             `--Xantusiidae MH11

*Type species of generic name indicated

REFERENCES

[BH10] Bell, C. J., M. G. Hollenshead, J. I. Mead & S. L. Swift. 2010. Presence of a urinary bladder in Egernia depressa (Squamata: Scincidae) in Western Australia. Records of the Western Australian Museum 25 (4): 459–462.

[CH97] Castro, P., & M. E. Huber. 1997. Marine Biology 2^nd ed. WCB McGraw-Hill: Boston.

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

[E01] Engel, M. S. 2001. A monograph of the Baltic amber bees and evolution of the Apoidea (Hymenoptera). Bulletin of the American Museum of Natural History 259: 1–192.

[E88] Evans, S. E. 1988. The early history and relationships of the Diapsida. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 1. Amphibians, Reptiles, Birds pp. 221–260. Clarendon Press: Oxford.

[F15] Fowler, H. W. 1915. Cold-blooded vertebrates from Florida, the West Indies, Costa Rica, and eastern Brazil. Proceedings of the Academy of Natural Sciences of Philadelphia 67 (2): 243–269.

[LBG12] Longrich, N. R., B.-A. S. Bhullar & J. A. Gauthier. 2012. Mass extinction of lizards and snakes at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences of the USA 109 (52): 21396–21401.

[MH11] Müller, J., C. A. Hipsley, J. J. Head, N. Kardjilov, A. Hilger, M. Wuttke & R. R. Reisz. 2011. Eocene lizard from Germany reveals amphisbaenian origins. Nature 473: 364–367.

[N10] Naish, D. 2010. Tetrapod Zoology: Book One. CFZ Press: Bideford (UK).

[RFN02] Raxworthy, C. J., M. R. J. Forstner & R. A. Nussbaum. 2002. Chameleon radiation by oceanic dispersal. Nature 415: 784–787.

[Sa05] Säilä, L. K. 2005. A new species of the sphenodontian reptile Clevosaurus from the Lower Jurassic of south Wales. Palaeontology 48 (4): 817–831.

[Sc05] Scanlon, J. D. 2005. Cranial morphology of the Plio-Pleistocene giant madtsoiid snake Wonambi naracoortensis. Acta Palaeontologica Polonica 50: 139–180.

[U57] Underwood, G. 1957. On lizards of the family Pygopodidae. A contribution to the morphology and phylogeny of the Squamata. Journal of Morphology 100 (2): 207–268.

[WH02] Worthy, T. H., & R. N. Holdaway. 2002. The Lost World of the Moa: Prehistoric life of New Zealand. Indiana University Press: Bloomington (Indiana).

Last updated: 11 August 2017.