A Comparative Study of the Arterial Systems of Some New World Crotalinae (Reptilia: Ophidia)

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The arterial systems of seven or eight latex-injected specimens, plus two uninjected specimens, of the following species were studied: Agkistrodon contortrix, A. piscivorus, Sistrurus catenatus, S. miliarius, Crotalus horridus, C. viridis and C. atrox. Six uninjected specimens of Lachesis muta, three of S. ravus, and one or two of each of 13 additional species of Crotalus were also used for studying pulmonary artery patterns. In general, the pulmonary artery patterns show a change from the dominant right pulmonary artery pattern in primitive Agkistrodon, to a modified version of this pattern in intermediate Sistrurus, to the right- left pulmonary artery pattern in advanced Crotalus, where the left pul- monary artery is dominant. However, S. ravus differs from S. catenatus and S. miliarius in its lung patterns, resembling the triseriatus group of the genus Crotalus. Laichesis has a large right and a small left pul- monary artery. This probably represents the earliest appearance of the right-left pulmonary artery pattern in the phylogeny of the North American Crotalinae. Primitive Agkistrodon usually feeds both the pterygoid and tem- poralis muscle complexes via the venom gland artery; Sistrurus does so partly via the venom gland vessel and partly by the facial carotid artery; Crotalus usually has both complexes fed by the facial carotid. The right side of the head of Agkistrodon differs from the left in its arterial ar- rangement. The number of branches from the left carotid artery to the esopha-