Family Amphisbaenidae s.l. (Worm Lizards), incl. Blanidae, Cadeidae and Rhineuridae

Order Squamata
Suborder Amphisbaenia

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Family Amphisbaenidae s.l. (Worm Lizards), incl. Blanidae, Cadeidae and Rhineuridae

Content: about 160 species in 18 genera (see list below).

Appearance: Amphisbaenians are limbless squamates whoses pectoral and pelvic girdles have been significantly reduced or are absent. Usually they have a distinctly annulated pattern of scutellation and rather short tails. Amphisbaenids are adapted to a burrowing life style and accordingly, their skulls are heavily ossified and their brain is entirely surrounded by the frontal bones. In contrast to other limbless lizards or snakes, which have a reduced left lung, the right lung of amphisbaenians is reduced in size.

Size: The total body length ranges from 10 cm to about 70 cm.

Distribution: Mostly Africa and South America with a few species in Europe and North America.

Habitat: Soil.

Behavior: Burrowing; The blunt-cone or bullet-headed genera (e.g., Amphisbaena, Blanus, Cadea Zygaspis) burrow by simple head-ramming. The spade-snouted taxa (Leposternon, Monopeltis) tip the head downward, thrust forward, and then lift the head. The Iaterally compressed keeled-headed taxa (Anops, Ancylocranium) ram their heads forward, then alternately swing it to the teft and right (Zug 1993).

Reproduction: usually oviparous, but some are live-bearing (namely some Loveridgea and Monopeltis).

Photo (left): Blanus cinereus; © Jakob Hallermann.

Relationships and sytematic notes: Rhineura is often put in a separate family, Rhineuridae. Kearney (2003) suggested to put Blanus in a separate family as well, the Blanidae, which can be diagnosed by their anteriorly truncated nasal bones and reduced clavicles (Kearney 2003).

Kearney (2003) also suggested to include the genera Aulura, Dalophia, Leposternon, and Monopeltis in the superfamily Rhineuroidea which she diagnosed by the following characteristics: strong craniofacial angle (also occuring in trogonophids), enlarged pectoral scales, a ventrally deflected retroarticular process, striated neural arches, denticulate posterior margins of the trunk vertebrae, ilium curving medially around anterior edge of vent, and an enlarged U-shaped occipital condyle.

Note that Kearney's Rhineuridae contains 1 extant genus, Rhineura, and 9 extinct genera (Dyticonastis, Hyporhina, Jepsibaena, Macrorhineura, Oligorhineura, Oligodontosaurus, Ototriton, Pseudorhineura, Spathorhynchus). Kearney's diagnosis of the Rhineuridae uses the following characteristics: small medial nasal process of premaxilla that does not separate the nasals in superficial view, a squared-off anterior edge of the snout, external naris opens ventrally, pterygoid-vomer contact, high maxillary tooth count, low maxillary tooth count, dentary process of coronoid overlapping dentary, and absence of posterodorsal rib processes. However, not all of these features can be ascertained in all the fossil taxa in this group.

Recently, Vidal et al. (2007) found that the genus Cadea is only distantly related to Amphisbaena in which it had been included previously. These authors erected a new family for the genus, Cadeidae Vidal & Hedges 2007.