Saturday, September 8, 2012

A Revision of the Lizards in the Family Teiidae

Dracaena guianensis and its unusual teeth, used for crushing 
mollusk shells. JCM
Genera in the New World lizard family Teiidae were spread out over several families before 1885 when Boulenger consolidated them  and organized them into four groups; Group I included macroteiids that shared nasals not separated medially by a frontonasal, well-developed limbs and a moderate to large body.  Boulenger's three remaining groups included various genera of microteiids that are currently assigned to the Gymnophthalmidae. Later, the macroteiids were placed in a separate subfamily containing two clades formally recognized as the tribes Teiini and Tupinambini by Presch. Little doubt remains that the Teiidae and Gymnophthalmidae are monophyletic groups, and today Presch’s clades are generally regarded as subfamilies. Recognition of these subfamilies has received mostly support from separate morphological analyses (chromosomal, hemipenial,  osteological,  integumental, myological, neurological) as well as mitochondrial DNA. A third subfamily Chamopsiinae accommodates extinct genera from North America and may be the sister group of the extant subfamilies. The Teiidae is almost certainly the sister group of the Gymnophthalmidae, and teiids likely arose in the middle Cretaceous from a common ancestor shared with the extinct Polyglyphanodontidae this group has been considered an additional subfamily of the Teiidae by some authors. The genus-level taxonomy of the Teiidae has long been unsatisfactory. This problem is particularly acute within the speciose radiation of cnemidophorines in which most tropical species are assigned to the large polyphyletic genera Ameiva and Cnemidophorus. Polyphyly urgently requires resolution, because teiids are often the most conspicuous elements of many New World herpetofaunas and have been the subject of numerous detailed ecological studies. As researchers make ecological comparisons among teiid species, draw inferences about their biogeography, propose conservation strategies, and conduct other studies of their comparative biology, polyphyly of genera such as Ameiva, Cnemidophorus, and Tupinambis will likely produce what have been called “error cascades,” where seemingly trivial taxonomic problems become magnified in the development of scientific knowledge. However, the problem is not just one of polyphyly. Some genera have never been adequately diagnosed, whereas others are defined by apparent symplesiomorphies. These problems contribute to misidentification in the field and incorrect or uncertain assignment of newly discovered species.

Salvator rufescens. JCM

Harvey et al. (2012) found that despite advances within particular groups, systematics of the Teiidae has long been unsatisfactory, because few morphological characters have been described for this family. Consequently, most species have been assigned to the large, polyphyletic, and poorly defined genera of Ameiva and Cnemidophorus. They describe 137 morphological characters and score them for most species of the Neotropical Teiidae. Important, but previously undescribed, character suites are detailed in the article and result in a new taxonomy of the Teiidae based on recovered evolutionary history and numerous morphological characters surveyed in this study. The authors recognize three subfamilies: Callopistinae new subfamily, Teiinae Estes et al., and Tupinambinae Estes et al. They resolve the polyphyly of Ameiva and Cnemidophorus, by establishing four new genera for various groups of Neotropical Teiidae: Ameivula new genus, Aurivela new genus, Contomastix new genus, and Medopheos new genus. They resurrect Holcosus Cope from the synonymy of Ameiva and Salvator Duméril and Bibron from the synonymy of Tupinambis. On the basis of shared derived characters, they propose new species groups of our redefined Ameiva and Cnemidophorus. We incorporate our new characters into a key to the genera and species groups of Teiidae. A phylogenetic hypothesis of Teiidae based on morphological characters differs substantially from hypotheses based on mitochondrial DNA. The phylogeny based on morphology is consistent with well-established biogeographic patterns of Neotropical vertebrates and explains extreme morphological divergence in such genera as Kentropyx and Aurivela.

Harvey, M.B., Ugento, G.N., Gutberlet, RL. 2012. Review of Teiid Morphology with a Revised Taxonomy and Phylogeny of the Teiidae (Lepidosauria: Squamata). Zootaxa 3459:1-156.

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