Phrynosoma cornutum

Williams et al. (2019) and Finger et al. (2022) found evidence from mtDNA, microsatellites, and genotyping-by-sequencing data for three primary and largely allopatric populations of Texas Horned Lizards in the Chihuahuan Desert, the Great Plains, and the southern Coastal Plain of the United States. Although they did not recognize these populations taxonomically, their demographic analyses indicate that the three populations are incompletely separated lineages. The earliest divergence is between the western (Chihuahuan Desert) and the two eastern populations. It corresponds to the divergence between the two primary mtDNA clades found by those authors and by Köhler (2021), who recognized them as subspecies (Nicholson 2025).

This species is widespread in the south-central United States and northern México. The population has suffered widespread declines due to habitat loss, habitat degradation, and the invasion of red imported fire ants. The population is likely still declining due to these threats.

The range extends from extreme southwestern Missouri and central Kansas to southeastern Colorado, and south and west throughout most of Oklahoma and Texas (including coastal barrier islands), eastern and southern New Mexico, and southeastern Arizona to northeastern Sonora, Chihuahua and Durango east of Sierra Madre Occidental, Coahuila, Nuevo Leon, Tamaulipas, San Luis Potosi, Zacatecas, and Aguascalientes (Price 1990, Arenas Monroy et al. 2014). Native eastern limit is uncertain; records for Missouri and Arkansas have been questioned (now extirpated from Arkansas; Trauth et al. 2004), and possibly the species is not native to Louisiana (Price 1990). Using Global Biodiversity Information Facility (GBIF) (2025) records, range extent is estimated to be 1,748,498 km² (RARECAT 2025).

This species has been introduced and is established in North Carolina (Settle 1989), South Carolina (Heuring et al. 2019), Florida (Owens and Krysko 2007, Krysko et al. 2019), and Hawaii (Hunsaker and Breese 1967, Price 1990).

This species is represented by hundreds of collection sites throughout the historical range in the United States and by well over 100 sites in Mexico (Prices 1990). Many historically occupied sites still support populations (e.g., Hammerson 1999).

The primary threats are mortality from fire ants, decline of native ant species, and habitat loss and degradation (Price 1990, Carpenter et al. 1993, Donaldson et al. 1994, Granberg et al. 2015).

Red imported fire ants (Solenopsis invicta) are implicated in declines of native harvester ants, an essential food source for this species (Pianka and Parker 1975, Henke and Fair 1998). The widespread use of broadcast insecticides is also thought to contribute to declines. Insecticides can be detrimental by directly causing illness or death or indirectly by severely reducing or eliminating harvester ants (Henke and Fair 1998). Fire ants are also implicated in predation of this species (Carpenter et al. 1993, Inslee 2010).

This species is vulnerable to changes in habitat. High densities of grasses and trees due to a lack of natural habitat disturbance is likely decreasing habitat quality (Anderson 2012, Granberg et al. 2015, Anderson et al. 2017). Development-related loss of shrubs and grasses, used as shade for thermoregulation, is also detrimental to survival (Tucker et al. 2023). Intensive ground disturbance, such as plowing and bulldozing, kills adults and their eggs (Carpenter et al. 1993, Donaldson et al. 1994, Anderson 2012). However, this species can thrive in altered habitats around small towns due to reduction in predators (Mirkin et al. 2021).

Mortality from road traffic is an important local threat in some areas. Males are particularly vulnerable during May-June in Arizona-New Mexico (Sherbrooke 2002). A high level of road mortality may lead to significant local declines (Anderson 2012). Road traffic on military installations also causes mortality (Webb and Henke 2008, Anderson 2012).

In the past, this lizard was collected for the pet trade, by boy scout troops for trading at jamborees, for the curio trade, and by tourists (Donaldson et al. 1994, Henke and Fair 1998).