Mitochondrial DNA Evidence and Evolution in Varanoidea (Squamata)

Varanoidea is a monophyletic group of anguimorph liz-the Bornean earless monitor (Lanthanotus borneensis), ards, comprising the New World helodermatids, the and the Old World monitors (Varanus).The earliest Bornean earless monitor Lanthanotus borneensis, and the fossils that can be clearly assigned to this group include Old World monitors (Varanus).I use mitochondrial DNA the Middle Cretaceous aigialosaurs (Carroll and sequences and extensive taxonomic sampling to test deBraga, 1992); later varanoid fossils include the alternative hypotheses of varanoid relationships.The helodermatid-like monstersaurians Gobiderma and most parsimonious hypothesis confirms the monophyly Estesia (Norell and Gao, 1997), the Lanthanotus-like of Varanoidea (Heloderma, Lanthanotus, and Varanus) Cherminotus (Gao and Norell, 2000), and the Varanusand Varanus, as well as the sister-taxon relationship of like Saniwides and Telmasaurus (Pregill et al., 1986).Varanus and Lanthanotus.The relationships among Vara-Currently, approximately 50 extant species of Varanus nus species differ in several respects from previous are recognized (Table 1).These species are found in hypotheses.Three major lineages are recognized within Africa; central and southern mainland Asia and Malay-Varanus: an African clade basal to the rest of the group, sian and Indonesian islands (these may be roughly an Indo-Asian clade, and an Indo-Australian clade.described as the Indo-Asian species); and Papua New Within the last lineage, the endemic Australian dwarf Guinea and Australia (where more than half the species monitors (Odatria) form a clade sister to the large Austraare found, henceforth referred to as the Indo-Australian monitors (the gouldii group).Tests of the effects lian species).All monitors share a basic body plan of rate heterogeneity and homoplasy demonstrate that and several morphological synapomorphies, yet the putative process partitions of data are largely congruent impressive diversity achieved by Varanus within its with one another and contribute positive support to the rather conservative overall morphology makes it an overall hypothesis.᭧ 2001