Xenosaurus rackhami

Xenosaurus rackhami, or Rackham's knob-scaled lizard, is a lizard found in Mexico and Guatemala.

Xenosaurus rackhami
Conservation status
Vulnerable (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Anguimorpha
Family:	Xenosauridae
Genus:	Xenosaurus
Species:	X. rackhami
Binomial name
Xenosaurus rackhami Stuart, 1941

Habitat

Xenosaurus rackhami inhabits humid, high-elevation cloud and oak forests in southern Mexico and Guatemala, with a range extending across Oaxaca and Chiapas into the Alta Verapaz Department. These lizards are specialized to rocky, moist microenvironments, utilizing narrow rock crevices and fissures for shelter, while relying on an habitat niche estimated at 16,200 square kilometers.

Behavior and diet

Xenosaurus rackhami is a highly specialized, diurnal, and sedentary crevice-dweller that relies heavily on rocky fissures for predator defense and thermoconforming behavior. It exhibits extreme site fidelity, rarely leaving its selected crevice.

Physical description

It is a medium-sized lizard characterized by a flattened body and head, which are evolutionary adaptations for navigating narrow rock crevices. The dorsal surface is covered in distinctive, enlarged knob-like scales (tubercles) interspersed with smaller granular scales. Its coloration typically consists of dark brown, olive, or grayish tones with irregular lighter crossbands along the back, providing effective camouflage against rock faces and leaf litter. The eyes feature distinct round pupils, and the limbs are well-developed with sharp claws adapted for gripping rocky surfaces.

Discovery

Xenosaurus rackhami was described by Laurence Cooper Stuart in 1941, based on a holotype from the Alta Verapaz Department of Guatemala. The species is named in honor of Horace H. Rackham and is considered a distinct species within the Xenosauridae family, following various taxonomic reevaluations.