Horned lizards (''Phrynosoma''), also known as horny toads or horntoads, are a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of North American

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

s and the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Phrynosomatidae The Phrynosomatidae are a diverse family of lizards, sometimes classified as a subfamily (Phrynosomatinae), found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny ...

. The

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

s refer directly to their horns or to their flattened, rounded bodies, and blunt snouts. The generic name ''Phrynosoma'' means "toad-bodied". In common with true toads (

amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbo ...

s of the family

Bufonidae {{Cat main, Toad This category contains both species commonly called toads, and the true toads from the family Bufonidae {{Cat main, Toad This category Category, plural categories, may refer to: Philosophy and general uses *Categorization, cat ...

), horned lizards tend to move sluggishly, often remain motionless, and rely on their remarkable camouflage to avoid detection by predators. They are adapted to arid or semiarid areas. The spines on the lizard's back and sides are modified

reptile scales Reptile skin is covered with scutes or scales which, along with many other characteristics, distinguish reptiles from animals of other classes. They are made of alpha and beta-keratin and are formed from the epidermis (contrary to fish, in which t ...

, which prevent water loss through the skin, whereas the horns on the head are true horns (i.e., they have a bony core). Of the 21 species of horned lizards, 15 are native to the USA. The largest-bodied and most widely distributed of the American species is the

Texas horned lizard The Texas horned lizard (''Phrynosoma cornutum'') is one of about 14 North American species of spikey-bodied reptiles called horned lizards, all belonging the genus '' Phrynosoma''. It occurs in south-central regions of the US and northeastern M ...

Defenses

Horned lizards use a variety of means to avoid

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

. Their coloration generally serves as

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

. When threatened, their first defense is to remain still to avoid detection. If approached too closely, they generally run in short bursts and stop abruptly to confuse the predator's visual acuity. If this fails, they puff up their bodies to cause them to appear more horned and larger, so that they are more difficult to swallow. At least eight species (''P. asio'', ''P. cornutum'', ''P. coronatum'', ''P. ditmarsi'', ''P. hernandesi'', ''P. orbiculare'', ''P. solare'', and ''P. taurus'') are also able to squirt an aimed stream of blood from the corners of the eyes for a distance up to . They do this by restricting the blood flow leaving the head, thereby increasing blood pressure and rupturing tiny vessels around the

eyelid An eyelid is a thin fold of skin that covers and protects an eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eye ...

s. The blood not only confuses predators, but also tastes foul to

canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...

and feline predators. It appears to have no effect against predatory

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s. Only three closely related species (''P. mcallii'', ''P. modestum'', and ''P. platyrhinos'') are certainly known to be unable to squirt blood. While previous thought held that compounds were added to the blood from glands in the ocular sinus cavity, current research has shown that the chemical compounds that make up the defense are already in the circulating blood. It is possible that their diet of large quantities of venomous

harvester ant Harvester ant, also known as harvesting ant, is a common name for any of the species or genera of ants that collect seeds (called seed predation), or mushrooms as in the case of '' Euprenolepis procera'', which are stored in the nest in commu ...

s could be a factor; however, the origin and structure of the chemicals responsible are still unknown. The blood-squirting mechanism increases survival after contact with canine predators; the trait may provide an evolutionary advantage. Ocular autohemorrhaging has also been documented in other lizards, which suggests blood-squirting could have evolved from a less extreme defense in the ancestral branch of the genus. Recent phylogenic research supports this claim, so the species incapable of squirting blood apparently have lost the adaptation for reasons yet unstudied. To avoid being picked up by the head or neck, a horned lizard ducks or elevates its head and orients its cranial horns straight up, or back. If a predator tries to take it by the body, the lizard drives that side of its body down into the ground so the predator cannot easily get its lower jaw underneath.

Population decline

University of Texas The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...

publication notes that horned lizard populations continue to disappear throughout their distribution despite protective legislation. Population declines are attributed to a number of factors, including the fragmentation and loss of habitat from real estate development and road construction, the planting of non-native grasses (both suburban and rural), conversion of native land to pastureland and agricultural uses, and pesticides. Additionally predation by domestic dogs and cats place continued pressure upon horned lizards. Fire ants ('' Solenopsis invicta'') introduced from South America via the nursery industry's potted plants, pose a significant threat to all wildlife including horned lizards. ''Phrynosoma'' do not eat fire ants. Fire ants kill many species of wildlife and are fierce competitors against native ants which horned lizards require for food (with their specialized nutritional content). Fire ants have given all ants a bad reputation and human attempts to eradicate ants, including invasive species and the native species on which the lizards prey, contribute to the continued displacement of native ant species and decline of horned lizards. The Texas horned lizard ('' Phrynosoma cornutum'') has disappeared from almost half of its geographic range. Their popularity in the early to mid 20th century pet trade, where collectors took thousands from the wild populations to sell to pet distributors, without provision for their highly specialized nutritional needs (primarily formic acid from harvester ants), resulted in certain death for almost all the collected lizards. In 1967 the state of Texas passed protective legislation preventing the collection, exportation, and sale of ''Phrynosoma'', and by the early 1970s most states enacted similar laws to protect and conserve horned lizards in the USA. However, as recently as the early 2000s the state of

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

still allowed commercial sale of ''Phrynosoma''. Despite limited federal protection in

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

, horned lizards are still offered in Mexican "pet" markets throughout the country. In 2014, the

Center for Biological Diversity The Center for Biological Diversity is a nonprofit membership organization known for its work protecting endangered species through legal action, scientific petitions, creative media and grassroots activism. It was founded in 1989 by Kieran Suckl ...

in Tucson petitioned the

Oklahoma Department of Wildlife Conservation The Oklahoma Department of Wildlife Conservation is an agency of the state of Oklahoma responsible for managing and protecting Oklahoma's wildlife population and their habitats. The Department is under the control of the Wildlife Conservation Com ...

to have the Texas horned lizard put on the endangered species list due to the massive declines of its population in Oklahoma, where it was once plentiful. The center said it may later seek protection for the animal on a federal level; it also said that reptiles in general are dying off at up to 10,000 times their historic extinction rate, greatly due to human influences.

Species and subspecies

The following 21 species (listed alphabetically by scientific name) are recognized as being valid by the

Reptile Database The Reptile Database is a scientific database that collects taxonomic information on all living reptile species (i.e. no fossil species such as dinosaurs). The database focuses on species (as opposed to higher ranks such as families) and has entrie ...

, three species of which have recognized

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all specie ...

: *

Giant horned lizard The giant horned lizard (''Phrynosoma asio'') is a species of phrynosomatid lizard which is endemic to the Pacific coast of southern Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern port ...

, ''Phrynosoma asio'' * Baur's short-horned lizard, ''Phrynosoma bauri'' (disputed; may be conspecific with ''P. hernandesi'') * San Diego horned lizard or Blainville's horned lizard ''Phrynosoma blainvillii'' * Short-tailed horned lizard, ''Phrynosoma braconnieri'' * Great Plains short-horned lizard, ''Phrynosoma brevirostris'' (disputed; may be conspecific with ''P. hernandesi'') * Cedros Island horned lizard, ''Phrynosoma cerroense'' *

, ''Phrynosoma cornutum'' *

Coast horned lizard The coast horned lizard (''Phrynosoma coronatum'') is a species of phrynosomatid lizard endemic to Baja California Sur in Mexico. As a defense the lizard can shoot high pressure streams of blood out of its eyes if threatened. Taxonomy It was ...

, '' Phrynosoma coronatum'' :*Cape horned lizard, ''P. c. coronatum'' :*California horned lizard, ''P. c. frontale'' :*Central peninsular horned lizard, ''P. c. jamesi'' * San Luis Valley short-horned lizard, ''Phrynosoma diminutum'' (disputed; may be conspecific with ''P. hernandesi'') *Ditmars' horned lizard or rock horned lizard, ''Phrynosoma ditmarsi'' * Pygmy short-horned lizard, ''Phrynosoma douglasii'' * Sonoran horned lizard, ''Phrynosoma goodei'' *

Greater short-horned lizard The greater short-horned lizard (''Phrynosoma hernandesi''), also commonly known as the mountain short-horned lizard, is a species of lizard endemic to western North America. Like other horned lizards, it is often called a "horned toad" or "horn ...

, ''Phrynosoma hernandesi'' *

Flat-tail horned lizard The flat-tail horned lizard (''Phrynosoma mcallii'' ) is a species of lizard in the family Phrynosomatidae. A species of reptile, it is endemic to the Sonoran desert of the southwestern United States and northwestern Mexico. Its multiple adapt ...

, ''Phrynosoma mcallii'' *

Roundtail horned lizard The roundtail horned lizard (''Phrynosoma modestum'') is one of the smaller species of horned lizard. Their specific epithet is from the Latin word ''modestum'', meaning modest or calm. They are found in the United States, in western Texas, New ...

, ''Phrynosoma modestum'' Horned lizards

* Mexican Plateau horned lizard or Chihuahua Desert horned lizard, ''Phrynosoma orbiculare'' :*''P. o. bradti'' :*''P. o. cortezii'' :*''P. o. dugesii'' :*''P. o. orbiculare'' :*''P. o. orientale'' * Desert short-horned lizard, ''Phrynosoma ornatissimum'' (disputed; may be conspecific with ''P. hernandesi'') * Desert horned lizard, ''Phrynosoma platyrhinos'' :*Southern desert horned lizard, ''P. p. calidiarum'' :* Northern desert horned lizard, ''P. p. platyrhinos'' * Guerreran horned lizard, ''Phrynosoma sherbrookei'' Nieto-Montes de Oca, Arenas-Moreno, Beltrán-Sánchez, & Leaché, 2014 * Regal horned lizard, ''Phrynosoma solare'' * Mexican horned lizard, ''Phrynosoma taurus'' ''Note'': In the above list, a

binomial authority In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bo ...

or trinomial authority in parentheses indicates that the species or subspecies was originally described in a genus other than ''Phrynosoma''.

Horned lizard (''Phrynosoma'') gallery

File:Coast Horned Lizard (9096387129).jpg, Blainville's horned lizard (''P. blainvillii)'' File:Phrynosoma braconnieri.jpg, Short-tailed horned lizard (''P. braconnieri)'', Oaxaca, Mexico (20 May 2013). File:Texas horned lizard (Phrynosoma cornutum), Armstrong County, Texas, USA (28 April 2013).jpg, Texas horned lizard (''P. cornutum''), Armstrong County, Texas, USA (28 April 2013) File:HORNED LIZARD, COAST (phrynosoma coronatum) (6-14-08) cerro alto north ridge, slo co, ca -01 (2579107136).jpg, Coast horned lizard (''P. coronatum''), San Luis Obispo County, California, USA (June 14, 2008) File:09-035 Horned Lizard (Phyrnosoma coronatum) (3481418737).jpg, Coast horned lizard (''P. coronatum'') (25 April 2009) File:Greater short-horned lizard on Seedskadee National Wildlife Refuge (27558656089).jpg, Greater short-horned lizard (''P. douglassi brevirostre''), Sweetwater County, Wyoming, USA (15 June 2016). File:Phrynosoma douglasii 4226.JPG, Pygmy short-horned lizard (''P. douglasii)'', Washington, USA (5 June 2014) File:Mountain short-horned lizard (Phrynosoma hernandesi), Culberson County, Texas, USA (19 May 2018).jpg, Mountain short-horned lizard (''P. hernandesi)'', Culberson County, Texas, USA (19 May 2018) File:Flat-Tailed Horned Lizard (5162160076).jpg, Flat-tailed horned lizard (''P. mcallii)'' (9 November 2010) File:Roundtail Horned Lizard (Phrynosoma modestum), Municipality of Tula, Tamaulipas, Mexico (15 August 2004).jpg, Round-tail horned lizard (''P. modestum''), Municipality of Tula, Tamaulipas, Mexico (15 August 2004) File:Mountain horned lizard (Phrynosoma orbiculare orientale), Municipality of Miquihuana, Tamaulipas, Mexico (24 September 2009).jpg, Mountain horned lizard (''P. orbiculare orientale''), Municipality of Miquihuana, Tamaulipas, Mexico (24 September 2009) File:Desert Horned Lizard in Mojave Desert.png, Desert horned lizard (''P. platyrhinos''), San Bernardino County, California, USA (9 July 2019) File:Horned lizard 032507 kdh.jpg, Regal horned lizard (''P. solare''), Apache Junction, Arizona, USA (25 March 2007)

Symbol

The genus of horned lizards is the official

state reptile Twenty-eight U.S. states have named an official state reptile. As with other state symbols, states compare admirable aspects of the reptile and of the state, within designating statutes. Schoolchildren often start campaigns promoting their fav ...

of Wyoming. Texas designated the Texas horned lizard (''Phrynosoma cornutum'') as the official state reptile in 1993Texas Horned Lizard
State Symbols USA. Retrieved on 2016-10-25. and the " TCU Horned Frog" is the mascot of

Texas Christian University Texas Christian University (TCU) is a private research university in Fort Worth, Texas. It was established in 1873 by brothers Addison and Randolph Clark as the Add-Ran Male & Female College. It is affiliated with the Christian Church (Discipl ...

in Fort Worth, Texas. TCU is the only known athletic team with the horned lizard as a mascot. File:Superfrog.jpg, The TCU mascot is commonly known as Super frog to TCU fans and students. He is usually present at TCU sporting events. File:HornedToad.png, Horned lizard on a necktie at El Paso, Texas, in 1940

References

External links

Horned lizard skulls and info at Digimorph.org

Horned Lizard Conservation Society

Horned Toads - Field study of Short-horned Lizards by students of Waterville Elementary School
{{Taxonbar, from=Q288720 Phrynosoma Symbols of Wyoming Lizards of North America Taxa named by Arend Friedrich August Wiegmann