Evolution and systematics

Lacertid lizards are the sister groups of teioids (teiids and relatives of the New World). Together they form the Lacer-tiformes. Molecular studies have allowed the recent recognition of three subfamilies, although the relationships of a number of genera (e.g., Takydromus) remain unresolved. The most primitive subfamily is the Gallotiinae, which comprises the giant lizards of the Canary Islands and the smaller, but closely related Psammodromas from Iberia and adjacent North Africa. They share a suite of unusual, but non-unique features, as well as the strange ability to squeak. The Eremiainae includes many genera endemic to the Ethiopian region. The basal genera occur in tropical forests (e.g., Holaspis, Gas-tropholis, and Poromera) or montane habitats (e.g., Adolfus and Tropidosaura), with a progression of more specialized genera showing increasing adaptation to arid habitats (e.g., Ichnotro-pis, Heliobolus, Meroles, Pedioplanis, Ophisops, Mesalina, and Acanthodactylus). The remaining subfamily, Lacertinae, includes the typical lacertids of Eurasia. The relationships and composition of many of the genera in the subfamily remain in question. The large genus Lacerta has long been para-phyletic but has been increasingly subdivided in recent years, with the creation of a number of genera and subgenera, e.g., Omanosaura, Timon, Darevskia, Caucasilacerta, Parvalacerta, and so on.

Lacertids are believed to have arisen in Eurasia and invaded Africa and the Ethiopian region, where they evolved more xeric forms (adapted to arid conditions). One or more derivatives then re-entered the dry areas of Eurasia. The fam ily has a long but fragmentary fossil history, extending back at least as far as the Palaeocene. Fragments of a recently described 120 million-year-old fossil lizard in amber from the Lower Cretaceous of Lebanon shows that common external features of lacertids and other autarchoglossan lizards had already evolved.

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