Evolution and systematics

Centers of abundance for the Crocodylidae are South America (four species), and the Indo-Pacific region (six species), although the family is postulated to have radiated from Africa in the Miocene epoch. Studies on the physiology of crocodiles have revealed that all species are able to concentrate and excrete salt, and this feature may well have aided in further spe-ciation via transoceanic migrations. Some adaptations for continued survival of the Crocodylidae are the position of the eyes and nostrils, parental care, and their cost-effective metabolisms, but they are capable of immense speed on land or in water when necessary. Morphological and molecular data support a close relationship between Crocodylus and Osteolaemus. In addition, the Indo-Pacific crocodilians (Crocodylus palustris, C. porosus, C. siamensis, C. novaeguineae, C. mindorensis, and C. john-stonii) are closely related. In the past, subspecies status has been proposed for both Crocodylus palustris and Crocodylus niloticus, but these were not recognized as of 2002. The addition of a new species to the family Crocodylidae, the Borneo crocodile (Crocodylus raninus,), has also not been recognized scientifically, pending further investigation. The New World species (Crocodylus acutus, C. intermedius, C. moreletii, and C. rhombifer) are a monophylectic assemblage, that is, they share a common ancestor. Two subfamilies are recognized: Crocodylinae, containing two genera and 12 species; and Tomistominae, containing one genus and two species.

Was this article helpful?

0 0

Post a comment