Greater Earless Lizard, Cophosaurus texanus

Greater Earless Lizard, Cophosaurus texanus. Photograph taken within a residential community in the greater Alamos area, Alamos, Sonora, April 2019. Photograph and identifications courtesy of David F Smith, Alamos, Sonora.

The Greater Earless Lizard, Cophosaurus texanus, is a member of the Phrynosomatidae family of North American Spiny Lizards, which include the Zebra-Tailed, Earless, Fringe-Toed, Spiny, Tree, Side-Blotched and Horned Lizards. The Phrynsomatidae Family consists of one hundred thirty-six members placed in nine genera. The Cophosaurus genus is monotypic, meaning Cophosaurus texanus is the only species in its genus. The Greater Earless Lizard are known in Mexico as Lagarto Sin Orejas Mayor.

Greater Earless Lizards are gray or brownish-slate in color, sometimes with a bluish tinge. They lack ear openings and their tail is flattened. Their dorsal scales are granular and uniform in size while their ventral scales are cycloid, smooth, flat, overlapping, and are approximately the same size as their tail scales. Two parallel black body bars mark their sides and extend transversely from their venter onto their dorsum posterior to the midline of their body and in front of their hind limbs. They have a row of 10 to 19 femoral pores on each thigh. Large black bands mark the underside of their tail, while the dorsal side of their tail has faint banding. Sexual dimorphism is displayed with males possessing numerous red, orange, and yellow dorsal spots scattered on their back that are more prominent laterally and fade toward their midline. Additionally, males have larger femoral pores, more prominent black body bars, and enlarged postanal scales. Conversely, females and juveniles sometimes possess dorsolateral rows of dark blotches on each side, and their body bars are weak or absent. Greater Earless Lizards reach up to 9 cm (3.5 inches) in snout-to-vent length, with males growing larger than females. 

Greater Earless Lizards are polygynandrous and mate from April to August, with peak activity in June. During mating season, males become more brightly colored and females often exhibit pink, orange, or yellow colors on their throats and sides. Males will defend a specific territory in order to mate with several females. They use body language such as lateral body compressions, push-ups, and head bobbing to claim their territory and attract females. Up to 4 clutches may be laid in a season, depending on the size of the female, beginning after their first winter. Each clutch contains 2 to 9 eggs that are laid after a gestation period of 25 to 35 days. Females then bury their eggs in warm sand to be incubated for 50 days until hatching. Peak hatching time occurs in July, however, hatchlings can be found as early as June and as late as October. Upon hatching, they measure 2.6 (1.0 inch) to 3.1 cm (1.2 inches) in snout-to-vent length with proportionally larger heads than adults. Hatchlings are precocial and are independent from birth. Apart from choosing a suitable nesting site, no parental care is provided. The Greater Earless Lizard  has a life span of five  years, although in the wild lizards that are over three years old are uncommon. 

Greater Earless Lizards are diurnal and spend much of their day basking in the sun. They are quite heat tolerant, maintaining an active body temperature of 37°C (99°F) to 41°C (106°F). At night they often wriggle into the sand just below the surface to stay warm. Seasonal activity begins in March and most adults disappear by early to mid-September, while Juveniles remain active into October. Greater Earless Lizards are insectivores and primarily consume adult and larval arthropods of various kinds, depending upon abundance. Beetles are seldom consumed, suggesting that their jaw musculature may not be capable of crushing hard exoskeletons. In turn, they are preyed upon by rattlesnakes, Greater Roadrunners, Common Nighthawks, and other large birds. When threatened, they rapidly dash away and flash the conspicuous, banded underside of their tail by curling it over their back when they are paused or slow to a stop. This behavior guides potential predators to attack their tail instead of their body. Additionally, Greater Earless Lizards can detach their tails to distract predators and allow the rest of them to escape if captured. Their tails will regrow, however, the regenerated tail is typically not the same size or color as the original tail. 

The Greater Earless Lizard may be confused with the Zebra-tailed Lizard, Callisaurus draconides (has external ear openings, dark body bars directly posterior to their front limbs, and their dorsal tail bands are more conspicuous; less abundant; less abundant on bajadas and lower slopes and more abundant in flats and valleys). 

From a conservation perspective, the Greater Earless Lizard is considered to be of Least Concern due to their wide distribution and presumed large population size. While no major threats have been identified for this species, habitat loss and degradation resulting from agricultural, residential, and commercial development has likely caused localized declines.