The altitude record is held jointly by Crotalus triseriatus in Mexico and Gloydius strauchi in China, both of which have been found above the treeline at over 4,000 m above sea level. They may be either arboreal or terrestrial, and at least one species (the cottonmouth, Agkistrodon piscivorus) is semiaquatic. Habitat Ĭrotalines are a versatile subfamily, with members found in habitats ranging from parched desert (e.g., the sidewinder, Crotalus cerastes) to rainforests (e.g., the bushmaster, Lachesis muta). In the Americas, they range from southern Canada southward to Central America to southern South America. The subfamily Crotalinae is found from Eastern Europe eastward through Asia to Japan, China, Indonesia, peninsular India, Nepal, and Sri Lanka. Contraction of this muscle, together with that of the muscularis compressor glandulae, forces venom out of the gland. Īmong vipers, these snakes are also unique in that they have a specialized muscle, called the muscularis pterigoidius glandulae, between the venom gland and the head of the ectopterygoid. Clearly, these organs are of great value to a predator that hunts at night, as well as for avoiding the snake’s own predators. The paired pit organs provide the snake with thermal rangefinder capabilities. Experiments have shown, when deprived of their senses of sight and smell, these snakes can strike accurately at moving objects less than 0.2 ☌ (0.36 ☏) warmer than the background. Having one of these organs on either side of the head produces a stereo effect that indicates distance, as well as direction. When prey comes into range, infrared radiation falling onto the membrane allows the snake to determine its direction. Succinic dehydrogenase, lactic dehydrogenase, adenosine triphosphate, monoamine oxidase, generalized esterases, and acetylcholine esterase have also been found in it. The membrane has many nerve endings packed with mitochondria. By controlling this tube, the snake can balance the air pressure on either side of the membrane. The two sections are connected via a narrow tube, or duct, that can be opened or closed by a group of surrounding muscles. The membrane is like an eardrum that divides the pit into two sections of unequal size, with the larger of the two facing forwards and exposed to the environment. It is deep and located in a maxillary cavity. The pit organ is complex in structure and is similar to the thermoreceptive labial pits found in boas and pythons. These loreal pits are the external openings to a pair of extremely sensitive infrared-detecting organs, which in effect give the snakes a sixth sense to help them find and perhaps even judge the size of the small, warm-blooded prey on which they feed. This subfamily is unique in that all member species share a common characteristic – a deep pit, or fossa, in the loreal area between the eye and the nostril on either side of the head. These snakes range in size from the diminutive hump-nosed viper, Hypnale hypnale, that grows to a typical total length (including tail) of only 30–45 cm (12–18 in), to the bushmaster, Lachesis muta, a species known to reach a maximum total length of 3.65 m (12.0 ft) in length. The type genus for this subfamily is Crotalus, of which the type species is the timber rattlesnake, C. The groups of snakes represented here include rattlesnakes, lanceheads, and Asian pit vipers. Currently, 23 genera and 155 species are recognized: These are also the only viperids found in the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Like all other vipers, they are venomous. The Crotalinae, commonly known as pit vipers, or pit adders, are a subfamily of vipers found in Eurasia and the Americas. Agkistrodontini Hoge & Romano-Hoge, 1983.Agkistrodontinii Hoge & Romano-Hoge, 1981.JSTOR ( June 2011) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.
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