Order Squamata
Suborder Serpentes (Ophidia)
Infraorder Henophidia (Boidea)

Families Tropidophiidae and Ungaliophiidae (Dwarf Boas)

Content: 3 subfamilies: Tropidophiinae, Ungaliophiinae, Xenophidioninae (but see note below)

Tropidophis h. haetianus © John C. Murphy

Appearance and morphology: Superficially, Dwarf Boas are intermediate between colubrids and boas. Cranially, they have two common carotid arteries, edentulous premaxillaries, longitudinally oriented maxillaries with solid teeth, and optic foramina that perforate the frontal-parietal sutures. The coronoid is reduced or absent, and the dentary bears numerous teeth. Hindlimb vestiges appear externally as cloacal spurs in males, and pelvic remnants occur in the trunk musculature except in Tropidophis semicinctus (and Xenophidion). Intracostal arteries arise from the dorsal aorta at nearly every trunk segment or at intervals of several segments. In contrast to related boids they have no or a substantially reduced left lung (in Ungaliophis); a tracheal lung is well developed. Both left and right oviducts are well developed too (modified after Zug et al. 2001).

Characteristics of subfamilies:

	Tropidophiinae	Ungaliophiinae	Xenophidioninae
dentary caninelike tooth	missing	missing	large (anterior)
hyoid horns	parallel	semiparallel	strongly divergent
pelvic remnants	present	present	absent

Size: Dwarf Boas are rather small boas, ranging from about 34 to 72 cm in lenght. Tropidophis melanurus from Cuba is an exception with a maximum length of more than 1 m.

Distribution: Middle and South America and on many Caribbean Islands. Xenophidion occurs in Malaysia and Indonesia.

Habitat: Tropidophiines are mostly terrestrial or semiarboreal forest inhabitants. Ungaliophiines occur in wet to dry forested habitats. Ungaliophis is arboreal or semiarboreal; Exiliboa placata is terrestrial, inhabiting mostly rocky habitats.

Behaviour: nocturnal (Trachyboa gularis is the exception and oviparous).Ungaliophiines are secretive snakes, likely nocturnal foragers.

Reproduction: Tropidophiines and Ungaliophiines are mostly viviparous, Exiliboa placata bears 8 to 13 neonates in September and October.

Food: Most Ungaliophiines species eat primarily amphibians and lizards, simply because rodents and birds are usually too big for them.

Taxonomic notes: Based on the significant differences in DNA sequence a new family, Ungaliophiidae, has been erected for the genera Exiliboa and Ungaliophis by Wilcox et al. (2002; see tree below). Dwarf Boas were previously included in the family Boidae as a subfamily, Tropidophiinae (e.g. Zug 1993). More recent authors consider them as separate family, Tropidophiidae (e.g. Pough et al., 1998). The genus Boella SMITH & CHISZAR 1992, formerly included in the Tropidophiidae, has been synonymized with Epicrates (Boidae).

Xenophidion has been considered as representative of a separate family, Xenophidionidae by WALLACH & GÜNTHER 1998 and more recently associated with the Bolyeridae by LAWSON et al. (2004).