Relationships of extant Crocodylia as inferred by sequence analysis of mitochondrial DNA

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1992-12

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Abstract

Despite many years of intense study, tiie relationships among living forms of crocodilians have remained uncertain. Molecular techniques have added resolution to these phylogeny estimates, and here I present the results of analyses using a 320 base-pair mitochondrial DNA fragment Higher level relationships were determined to be concordant with all other molecular estimates, including analyses of blood proteins. These molecular analyses support the alignment of the false gharial, Tomistoma schlegelii with the true gharial, Gavialis gangeticus. Also, these two genera appear to have diverged from the clade containing Crocodylidae (the true crocodiles) subsequent to a divergence from the AlUgatoridae. The black caiman, Melanosuchus niger was found to be most closely related to Caiman, with Paleosuchus as sister to the former two genera. Alligator mississippiensis and Alligator sinensis form a monophyletic sister group to all of the caimans (Caiman. Melanosuchus. and Paleosuchus). The two new world Crocodylus. C. acutus and C. intermedius appeared as sister taxa that were aligned with the cuban crocodile, C. rhombifer. The other new world Crocodylus. C. moreletii. was aligned with C. niloticus. The Indo-Pacific forms, C. novaeguineae and C. mindorensis were also found to be sister taxa, as were closely related C. porosus and C. siamensis. The two subspecies of Osteolaemus have diverged more from each other than between many other species within Crocodylus or the caimans.

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Keywords

Crocodylidae -- Genetics, Extinct amphibians -- Genetics, Nucleic acid hybridization

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