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

Belongs within: Lepidosauromorpha.
Contains: Sphenodontia, Amphiglossus, Pachydactylus, Iguania, Polyglyphanodontia, Gekkota, Lacertoidea, Anguimorpha, Scincomorpha, Mosasauridae.

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.

    |    |  i. s.: PalacrodonE88
    |    |         PolysphenodonE88
    |    |         PelecymalaE88
    |    |--Gephyrosaurus bridensis Evans 1980Sa05
    |    `--SphenodontiaSa05
    `--Squamata [Ascalabota, Autarchoglossa, Lacertibaenia, Scleroglossa, Typhlophthalmi]MH11
         |  i. s.: Moanasaurus [incl. Rikisaurus]WH02
         |           |--‘Mosasaurus’ flemingiWH02
         |           |--M. mangahouangaeWH02
         |           `--‘Rikisaurus’ tehoensisWH02
         |         Haasiasaurus [=Haasia]Sc05
         |           `--H. gittelmani [=Haasia gittelmani]Sc05
         |         Timon lepidusN10
         |         Aporosaura anchietaeBH10
         |         Constrictor constrictorU57
         |         Takydromus smaragdinusMH11
         |         AmphiglossusMH11
         |         BrachymelesMH11
         |           |--B. gracilisMH11
         |           `--B. talinisMH11
         |         Pygomeles braconnieriMH11
         |         Neoseps reynoldsiMH11
         |         Scincopus fasciatusMH11
         |         SphenopsMH11
         |           |--S. boulengeriMH11
         |           `--S. sphenopsiformisMH11
         |         Sepsina angolensisMH11
         |         Mesaspis moreletiMH11
         |         Sauresia agasepsoidesMH11
         |         Wetmorena haetianaMH11
         |         Meroles cuneirostrisMH11
         |         Tracheloptychus madagascariensisMH11
         |         Angolossaurus skoogiMH11
         |         Chaemasaura anguinaMH11
         |         Hyphalosaurus Gao, Tang & Wang 1999D07
         |           `--H. lingyuanensisD07
         |         Monjurosuchus Endo 1940 [Monjurosuchidae]D07
         |           `--M. splendens Endo 1940B93
         |         Stilosoma extenuatumF15
         |         LygodactylusP92
         |           |--L. capensisH25
         |           `--L. groteiP92
         |         Pristurus rupestrisH25
         |         Paravaranus [Paravaranidae]B93
         |           `--P. angustifrons Borsuk-Bialynicka 1984B93
         |         Bainguis [Bainguidae]B93
         |           `--B. parvus Borsuk-Bialynicka 1984B93
         |         Harpesaurus ensicaudaB28
         |         Oreocephalus amblyrhynchusM01
         |         PachydactylusL51
         |         Rhoptropus boultoniL51
         |         Cremastosaurus Cope 1873SH96
         |           |--C. carinicollis Cope 1873 (n. d.)SH96
         |           `--C. rhambastes (Cope 1884) (n. d.) [=Platyrhachis rhambastes]SH96
         |         Diacium Cope 1873SH96
         |           `--D. quinquepedale Cope 1873 [=D. quinquepedalis, D. sesquipedale (l. c.)]SH96
         |         Platydactylus minutusP92
         |         Holaspis guentheriP92
         |         NucrasN00
         |           |--N. boulengeri Neumann 1900N00
         |           `--N. delalandiiN00
         |         Platyurus platyurusS72
         |         OphisopsP72
         |           |--O. elegansLK03
         |           |    |--O. e. elegansLK03
         |           |    |--O. e. blanfordiLK03
         |           |    `--O. e. ehrenbergiLK03
         |           `--O. jerdoni Blyth 1853P72
         |         Hemisphaeriodon Peters 1867LF96
         |         Chirotes lumbricoidesJ23
         |         Liolepis belliM90
         |--Dibamidae [Dibamia]MH11
         |    |--Anelytropsis [Anelytropsidae]Sc05
         |    `--Dibamus novaeguineaeMH11
            |  `--Lamiasaurus Longrich, Bhullar & Gauthier 2012LBG12
            |       `--*L. ferox Longrich, Bhullar & Gauthier 2012LBG12
                  |  `--+--LacertoideaLBG12
                  |     `--+--AnguimorphaLBG12
                  |        `--ScincomorphaLBG12
                     |  `--AigialosauridaeL05
                     |       |--Proaigialosaurus huenei Kuuhn 1958B93
                     |       |--Aigialosaurus dalmaticus Kramberger 1892LBG12, B93
                     |       |--Carsosaurus marchesetti Kornhuber 1893B93
                     |       |--Vallecillosaurus donrobertoiVF21
                     |       `--Opetiosaurus Kornbuber 1901D07
                     |            `--O. buccichi Kornhuber 1901B93
                             |--Coniasaurus crassidens Owen 1850B93
                             |--Acteosaurus tommasini Meyer 1860B93
                             |--Eidolosaurus Nopcsa 1923B93
                             |--Dolichosaurus Owen 1850D07
                             |    `--D. longicoliis Owen 1850B93
                             `--Pontosaurus Kramberger 1892LBG12, D07
                                  `--P. lesinensis Kornhuber 1873B93

*Type species of generic name indicated


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[SH96] Sullivan, R. M., & J. A. Holman. 1996. Squamata. In: Prothero, D. R., & R. J. Emry (eds) The Terrestrial Eocene–Oligocene Transition in North America pp. 354–372. Cambridge University Press.

[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.

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