A monographic study of the colubrid snake genus Leptodeira. Bulletin of the AMNH ; v. 114, article 1

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New York : [American Museum of Natural History]
"The genus Leptodeira Fitzinger, 1843, includes as absolute synonyms the generic names Megalops Hallowell, 1861, Anoplophallus Cope, 1893, and Pseudoleptodeira Taylor, 1938. Nine species comprise the genus; five of these are monotypic; one embraces five subspecies, one includes four subspecies, and two others each contain three subspecies, making a total of 20 forms. Two subspecies are described as new in this paper. The genus is characterized by maxillary teeth that increase in size posteriorly followed by a diastema and two enlarged, grooved fangs. There are two apical pits, elliptical pupil, divided anal, smooth dorsal scales, normal complement of colubrid head shields, and a capitate hemipenis with many large spines. Four species groups are separated on the nature of the hemipenes, the dentition and certain skull elements, particularly the quadrates, vomers, and maxillaries. Analysis of the characters shows that the most useful in a systematic study of the snakes are the numbers of ventrals, caudals, and dorsal scale rows, the numbers of upper labials and preocular scales, the number, shape, and size of the body blotches, and the nature of the dorsal head pattern. Analysis of numerous character clines shows that parallel clines may exist in two or more species in certain characters, but that in others the clines may diverge. Discontinuous clines are common. In some cases these are correlated with striking morphological changes between populations and become incorporated in the characteristics of subspecies. Studies of the skull of Leptodeira indicate that the skull is a normal colubrid type without striking specializations. Certain skeletal elements readily identify it from related genera. The poison glands (modified posterior portions of parotid glands) are large and produce a venom of sufficient strength to kill small frogs and lizards. The distribution of the genus is essentially throughout the American tropics to elevations of about 2000 meters. Some forms are restricted to semi-arid habitats; others live in tropical rain forest. Two species range from semi-arid to wet forest environments; each has a subspecies adapted to arboreal life in the forest by having a reduced number of dorsal scale rows, enlarged vertebral and paravertebral scale rows, and a laterally compressed body. Snakes of this genus feed primarily on frogs and toads; some lizards are included in the diet. The snakes are nocturnal and appear to reach their greatest abundance at times of congregations of breeding frogs. So far as is known, all species are oviparous and may lay as many as 13 eggs. On penial characters Leptodeira may be placed with Hypsiglena and Trimorphodon as a subgroup of colubrine snakes. If Leptodeira is related to Trimorphodon, they must have diverged early in their evolutionary history. Hypsiglena and Leptodeira are closely related and evolved from a common ancestral stock. The African snakes of the genus Crotaphopeltis that have been placed in the genus Leptodeira represent a separate evolutionary line of colubrine snakes. Based on the Cenozoic history of tropical America, studies of the morphology and distribution of the snakes, and the fossil record of other animals, the evolutionary history of Leptodeira has been reconstructed. This shows that Leptodeira and Hypsiglena underwent generic differentiation from a common ancestral stock in southern México during the early Miocene. By middle Miocene time the groups of Leptodeira had diverged. The present distribution and differentiation are a result of the effects of sea portals across Middle America that isolated populations often for long periods of time, and the Cenozoic orogenies that changed the uniform climatic conditions of Middle America and produced arid as well as humid habitats"--P. 143.
152 p., 31 p. of plates : ill., maps ; 27 cm.
Thesis (Ph. D.)--University of Michigan.
Includes bibliographical references (p. 144-150) and index.