Family Xenosauridae and Shinisauridae

Order Squamata
Suborder Anguinomorpha

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Family Xenosauridae and Shinisauridae

Xenosaurus platyceps
© Wayne van Devender

The Xenosauridae consist of the Central American genus Xenosaurus and of two fossil North American genera, Exostinus and Restes, which are very close to Xenosaurus.

The status of the Chinese genus Shinisaurus is not completely clear. Macey et al. (1999) recently suggested to split the Xenosauridae into two separate families, the Sinisauridae and Xenosauridae, because of DNA sequence differences. Xenosaurids are rock-dwelling lizards. All species are diurnal and viviparous. Shinisaurus is special in that it is semi-aquatic and is known to feed on tadpoles and fish.

Zoological definition: The temporal arches are strongly developed, and the temporal openings are large and not roofed by skull bones. The bones of the skull are roughened by the fusion to them of the cranial osteoderms (Goin et al. 1978).

Cranial features:

• Cephalic scales relatively small,
• Cephalic osteodermal crust divided into conical mounds;
• Frontals constricted between orbits;
• Rectangular cross-section of skull owing to presence of canthal crest on temporal arch;
• Widened and sculptured postorbital branch of jugal;
• Jugal-squamosal contact on temporal arch;
• Ectopterygoid exposed laterally on skull;
• Carotid fossa reduced (after Borsuk-Bialynicka, 1986).