Evolution and systematics

One of the earliest lizards to show some of the features of geckos is the late Jurassic Eichstaettisaurus from Germany. Although it was similar to modern geckos in general appearance, it lacked the derived features that characterize the living forms, and its true affinities remain the subject of controversy. The oldest definitive gecko represented in the fossil record is Hoburogecko suchanovi, which lived in Mongolia about 100 million years ago. Tertiary gecko fossils as well as geckos imbedded in amber have been recorded from numerous localities around the world, and many of them belong to living genera.

Geckos constitute the bulk of the Gekkota, the sister group of the Autarchoglossa and one of the three major lineages of lizards. Some researchers regard the xantusiids, dibamids, and amphisbaenids as allied to the geckos, but the evidence is equivocal. Geckos (including pygopods) are partitioned into 116 genera in four subfamilies: the Eublephar-inae (22 species), Diplodactylinae (121 species), Gekkoninae (930 species), and Pygopodinae (36 species), each of which is sometimes treated as a separate family. Morphologic features and at least some DNA sequence evidence support the Eu-blepharinae as the sister group of the remaining geckos. The diplodactylines, which are restricted to Australia, New Caledonia, and New Zealand, are allied most closely to the py-gopodines, which occur chiefly in Australia, with two species reaching New Guinea. Of the four subfamilies, Gekkoninae contains the greatest number of species and has, by far, the widest distribution, occurring throughout the tropics and sub-tropics worldwide. The origin of the major clades within the

Gekkonidae may be linked to the breakup of the supercontinent of Pangea in the late Jurassic and the subsequent fragmentation of the southern continent of Gondwana during the Cretaceous and early Tertiary.

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