boa

 

(bō'ə) , name for live-bearing constrictor snakes of the family Boidae, found mostly in the Americas. This family, which also comprises the egg-laying pythons of the Old World, includes the largest of all snakes, as well as many smaller ones. Members of the boa family have two functional lungs instead of one, as is found in other snakes, and vestiges of hind limbs; these primitive characteristics are indicative of their relationship to lizards. Each of the two tiny, internal leg bones ends in an external horny claw; the claws are much more prominent in males than in females. Boas capture their prey by striking with their teeth and simultaneously throwing their bodies in a coil around the victim. They then squeeze the animal so that, unable to expand its rib cage, it suffocates. Like other snakes, boas swallow the prey whole. Over 30 boa species are found from Mexico to South America, with the greatest variey in the tropics, and two in the United States. Boas may be terrestrial, arboreal, or burrowing. Some are brightly colored, like the green and white emerald tree boa of the tropics (Boa canina), or iridescent, like the wide-ranging rainbow boa (Epicrates cenchris). Best known is the boa constrictor (Constrictor constrictor), which lives in a variety of terrestrial habitats from S Mexico to central Argentina. It averages 6 to 9 ft (1.8–2.7 m) in length, occasionally reaching 14 ft (4.3 m), and has dark brown diamond markings on a lighter background. The South American anaconda (Eunectes murinus) is a semiaquatic boa that inhabits swamps and river shallows, catching animals that come to drink. The longest member of the boa family and the thickest of all snakes, it may reach 25 ft (7.9 m) in length and 3 ft (90 cm) in girth. The rubber boa (Charina bottae) is found in moist regions of the far W United States and extreme SW Canada. It is a burrower, about 18 in. (46 cm) long, with a narrow, blunt head, broad, blunt tail, and silver-green skin. It feeds chiefly on lizards and rodents. The rosy boa (Lichanura roseofusca) is found in chaparral in the SW United States and N Mexico; it grows about 3 ft (90 cm) long. It has large, dark brown spots on a lighter background. Several species of sand boa (Eryx) are distributed from India and central Asia to N Africa and SE Europe; all are burrowers in sand. There are also several boa species on Madagascar and several on Pacific islands. Boas are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Squamata, family Boidae.

Boidae
Red-tailed Boa, Boa constrictor
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Squamata Suborder: Serpentes Family: Boidae Gray, 1825
Genera
Acrantophis Boa Candoia Corallus Epicrates Eryx Eunectes Gongylophis Sanzinia

Boas are a type of snake that are members of the Boidae family. Boas are basal snakes that are "primitive" in evolutionary terms (i.e. less derived). They are constrictors and most give birth to live young. They have anal spurs, a pair of claws on each side of the cloaca which assist in mating. Boas are named after cows (Latin: bos) because of the old myth that boa snakes pursue cows and suckle them until they are drained to death.

Boas have two subfamilies: Boinae or true boas and Erycinae or sand boas. Pythons are sometimes classified as a subfamily of Boidae, but are frequently listed under their own family, Pythonidae. Sand boas are also frequently listed under their own family, Erycidae.

Boinae subfamiliy

Snakes of the subfamily Boinae are found in Madagascar, Papua, Pacific Islands, and the Neotropics. It has been suggested that genera within each of these particular areas do not form monophyletic groups. True boas are medium to large sized snakes. Females are usually larger than their males. Boas contain many subspecies based on locality. The boas from the Amazon Basin are the most colorful possessing bright cherry red tails. It used to be said that boas were New World Snakes and pythons were Old World Snakes, but, with boas found on Madagascar, Fiji, and Solomon Islands, this is not quite true. Instead, it is possible that boas have survived in evolutionarily isolated areas. South America, until a few million years ago, had a distinct fauna that included marsupial mammals; with the land bridge to North America, boas have migrated north as placental mammals and colubrids have migrated south.

• Boa (one species: Boa constrictor, also called the Red-tailed Boa, )
• Acrantophis (Dumeril's Boa and Madagascar Ground Boa; sometimes equated with Boa)
• Sanzinia (Madagascar Tree Boa; sometimes equated with Boa)
• Eunectes (Anacondas)
• Corallus (Tree boas)
• Epicrates (Rainbow boas)
• Candoia (Pacific boas)

Erycinae subfamiliy

Compared to true boas, erycines are quite small, with most members remaining well under a meter in length. Fossil erycines have been found in rock strata over 50 million years old, and were once widespread in North America. Now, only two species remain in North America, as well as the sand boas in Africa, Asia and southeastern Europe.

At least three erycine species lay eggs: the Calabar Boa, (Calabaria reinhardtii) (once classified as a python for this reason); the Arabian Sand Boa, (Eryx jayakari); and the West African Sand Boa, (Eryx muelleri).

• Eryx (Sand boas)
• Gongylophis (Rough-tailed Sand Boa)
• Charina (Rubber Boas)
• Lichanura (Rosy boa, sometimes equated with Charina)
• Calabarinae (Calabar Python, sometimes equated with Charina)

External links

• Red-Tail Boa Frequently Asked Questions
• General Information on Boas
• The Sand Boa Page

Snake families
Chordata • Reptilia • Squamata
Alethinophidia	Acrochordidae • Aniliidae • Anomochilidae • Atractaspididae • Boidae • Bolyeriidae • Colubridae • Cylindrophiidae • Elapidae • Loxocemidae • Pythonidae • Tropidophiidae • Uropeltidae • Viperidae • Xenopeltidae
Scolecophidia	Anomalepididae • Leptotyphlopidae • Typhlopidae

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