| Xenosaurus grandis | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Family: | Xenosauridae |
| Genus: | Xenosaurus |
| Species: | X. grandis |
| Binomial name | |
| Xenosaurus grandis (Gray, 1856) | |
 | |
| Synonyms [2] | |
Xenosaurus grandis, commonly known as the knob-scaled lizard, is a species of diurnal, terrestrial lizard endemic to Mexico and Guatemala. It primarily inhabits tropical rainforests. It dwells in rock crevices and eats insects.
The scientific name, Xenosaurus grandis, comes from the Greek words xenos, meaning “alien”, “stranger”, or “foreigner”, saurus, meaning “lizard”, and grandis, meaning “grand” or “great”. Its common name, “knob-scaled lizard”, refers to the bumpy, “knob-like” scales found on the upper portion of its body. [3]
There are five recognized subspecies, which are spread throughout the species’ range, and the species complex is being reevaluated. Some of the subspecies are currently in the process of being elevated to species status. The species as a whole is listed as vulnerable by the IUCN Red List and its population is currently decreasing. [1]
Xenosaurus grandis has a flattened head and body and is nearly always found in rock crevices, or at least with a portion of the body in a crevice. [4] Its flattened physiology is most likely an adaptation to allow it to squeeze into narrow crevices. Its color ranges from dark grey to dark brown, with lighter bands or blotches. It has a forked tongue, and small, sharp, fang-like teeth. [5]
On average, the snout-vent length (SVL) of Xenosaurus grandis is 6.8 - 12.9 cm. [6] While some species of Xenosaurus do not exhibit sexual dimorphism, Xenosaurus grandis, among other species, is one that does. In Xenosaurus grandis, males and females do not differ significantly in body size, but males have proportionately larger heads (in length and width) than females. Males and females of X. grandis do not exhibit a significant difference in femur length or head shape. [6]
Xenosaurus grandis is a diurnally active thermal conformer, meaning that its body temperature correlates with substrate and air temperatures. Its average body temperature is 22.7 C. [7] Air and substrate temperatures may be particularly relevant in Xenosaurus grandis since they are almost exclusively ground and crevice dwellers. Temperatures seem to differ across Xenosaurus species, possibly because of environment and habitat. Xenosaurus grandis appears to inhabit more dense tropical forests, where sunlight may not reach the ground as much. [8] While body temperature is influenced by the lizard's amount of cover and its body position in its crevice, it does not seem to be influenced by sex, month, vegetation type, or any crevice characteristics. [8]
Lizards in the genus Xenosaurus are exclusively found in crevices. Such a lifestyle suggests that the diets of these lizards might be opportunistic, and they eat whatever crawls or flies past or into their crevice. [9] Their diet consists primarily of insects, but occasional lizard prey are taken. [7] Their most frequent prey includes coleopterans (beetles), dipterans (flies), orthopterans (insects such as grasshoppers, crickets, weta, and locusts), and myriapods (terrestrial arthropods such as millipedes and centipedes). On the basis of number, they consume the most dipterans, but on the basis of volume, they consume the most orthopterans. [9]
The Knob-scaled lizard is diurnal, meaning it is active during the day. [7] Due to its diet of Orthoptera and Lepitdoptera larvae, Xenosaurus grandis is an ambush predator. It waits in its rocky crevice home and strikes with the element of surprise. [7] It is a very solitary and aggressive species and will often fight with members of its own species over territory. [7]
Xenosaurus grandis and the rest of the xenosaurids are viviparous, which means offspring are birthed live rather than in eggs. Young are birthed after a 9-month gestation period. The majority of litters contain only three offspring, but litters ranging from two to seven offspring have also been observed. [9] Male knob-scaled lizards reach maturity at 28 months, while females reach maturity a little later, at 32 months. [10] It is also plausible to say that X. grandis do not produce young every year. [11]
There are five major population areas for the Xenosaurus grandis in Southern Mexico and Guatemala: central Veracruz, southern Oaxaca, north-central Oaxaca, the highlands of central Chiapas, and central Guatemala. [1] The separate population areas have given rise to five subspecies of X. grandis. The five subspecies are X. g. grandis, X. g. agrenon, X. g. arboreus, X. g. rackhami, and X. g. sanmartinesis. [2]
All the subspecies of Xenosaurus grandis live exclusively in rock crevices, which allows them to live in many habitats, including: xerophytic vegetation, tropical rainforests, cloud forests, oak forests, and tropical deciduous rainforests. [1] The lizards have strong attachments to where they live, only living in 1-2 rock crevices for 95% of their entire lives. [4]
Currently Xenosaurus grandis is categorized as a vulnerable species according to the IUCN. [1] The species was given this status because of fragmented populations, decreasing population size, and decreasing habitat quality and area, covering only 20,000 square km. The greatest threats to the survival of the species in the wild are habitat destruction and trapping for international pet trade. Eagles are the greatest natural predator of X. grandis, but they are not considered a threat to the survival of the species as a whole. [1] Also, warmer temperatures in their habitat have been shown to cause greater mortality rates among the lizards, posing another potential threat to the species. [4]
Higher temperatures have been associated with higher mortality rates for X. grandis. In the 2003-2004 wet season of Southern Mexico and Guatemala (the habitat regions of the species), the average temperature was 24.3 C. That temperature was in the top 12% of highest recorded temperatures in the past 34 years of record keeping. [4] The mortality rate for yearlings (the youngest age group) increased from 0.1923 to 0.6551 and for adult II (the oldest age group) increased from 0.3956 to 0.5676 for the 2002-2003 and 2003-2004 wet seasons respectively. [4] If temperatures continue to increase, the survival of the species will be further threatened and currently 50% of wet seasons are warm enough to be considered to be unfavorable for the species. [4]
As of 2004, X. grandis had a survival rate of 70.5% and a growth rate of 0.851. Even though the rates may appear to be low, in comparison to other lizard genera and families X. grandis is doing well. Currently the species is decreasing in population, which is thought to be primarily caused by human development destroying their habitat. If habitat destruction stops, the population should at least be stable, if not prosperous. [4]
Xenosauridae is a family of anguimorph lizards whose only living representative is the genus Xenosaurus, which is native to Central America. Xenosauridae also includes the extinct genera Exostinus and Restes. Also known as knob-scaled lizards, they have rounded, bumpy scales and osteoderms. Most living species prefer humid, rocky habitats, although they are widespread within their native regions, with some inhabiting semi-arid scrub environments. They are carnivorous or insectivorous, and give birth to live young.
The greater earless lizard is the only species in the monotypic genus Cophosaurus. It is closely related to the smaller, lesser earless lizards and other species in the genus Holbrookia, and in fact was placed in that genus and referred to Holbrookia texana from 1852 into the 1970s. Earless lizards lack external ear openings, an adaptation to burrowing in the sand, as are the recessed lower jaw and flared upper labial scales. Greater earless lizards are sexually dimorphic, males grow larger and are more colorful than females, exhibiting pink and green colors that are particularly bright in the breeding season. Two bold black bars mark the lateral region of males but are greatly reduced and vague, or occasionally entirely absent in females.
The Mexican blind lizard is a species of legless lizard in the family Dibamidae, and the only species in the genus Anelytropsis. It is endemic to Mexico. They look like Amphisbaenia, but are in fact, only distantly related.
Xenosaurus is a genus of lizards; it is the only extant genus in the family Xenosauridae, with 14 species currently recognized. Also known as knob-scaled lizards, they can found in southwestern Tamaulipas and eastern Guerrero in Mexico. These lizards are known to feed on a variety of crawling and flying insects. This genus mostly eats orthopterans, coleopterans (beetles), dipterans, and myriapods.
The Sudan plated lizard, also known as the western plated lizard, great plated lizard, or Broadley's rough-scaled plated lizard, is a medium-sized, diurnal African lizard.
Xenosaurus rectocollaris, sometimes known as the pallid knob-scaled lizard, is a species of viviparous lizard. It is endemic to Mexico where it is known from the Sierra Madre de Oaxaca of Oaxaca and Puebla states. It is a rare species occurring in rock crevices in pristine semi-arid areas.
Sceloporus poinsettii, the crevice spiny lizard, is a species of small, phrynosomatid lizard.
Sceloporus merriami, commonly known as the canyon lizard, is a species of lizard in the family Phrynosomatidae. The species is native to the south-western United States and northern Mexico.
Ophryacus undulatus is a venomous pitviper species found in the mountains of central and southern Mexico. No subspecies are currently recognized.
Ctenosaura acanthura, is a species of iguanid lizard found in eastern Mexico and extreme western Guatemala. The standardized English name is the Mexican spiny-tailed iguana. Confusingly however, an earlier edition of standardized names for Mexican herpetofauna called Ctenosaura acanthura the northeastern spinytailed iguana and applied the name Mexican spinytailed iguana to Ctenosaura pectinata, which was called the western spiny-tailed iguana in the second edition. It has also been referred to as the Veracruz spiny-tailed iguana and Gulf Coast spiny-tailed iguana. It is an egg laying species that is mostly herbivorous and a moderately large lizard commonly growing over one meter in total length.
The Baja blue rock lizard is a species of large, diurnal phrynosomatid lizard.
Xenosaurus platyceps, the flathead knob-scaled lizard, is a lizard found in the Sierra Madre Oriental of Mexico. Its natural habitat is dry scrub forest and oak savanna. The species is endangered due to habitat fragmentation for the development of tourism and agriculture as well as predation by feral cats. Currently, the flathead knob-scaled lizard does not live in a protected area. Temperature plays a large part in growth rates of Xenosaurus Platyceps along with genetic factors. It has been found that the flathead knob-scaled lizards living in lower elevation, in a more tropical environment, grow virtually twice as fast as those from higher elevations, in a more temperate environment.
The bolsón night lizard is a species of night lizard in the family Xantusiidae. The species, which was originally described by Robert G. Webb in 1970, is endemic to the state of Durango in Mexico. Not much is known about the lizard at present, as it appears to be simultaneously rare and rather secretive in nature.
Aspidoscelis costatus, also known as the western Mexico whiptail, is a species of whiptail lizard endemic to Mexico, including Guerrero, Morelos, and Puebla in southern Mexico, as well as other Mexican states. Its range spans both temperate and tropical habitats, and even densely populated urban areas. Its common name, the Western Mexico Whiptail, can easily be confused with the Western Whiptail, which refers to a different lizard, Aspidoscelis tigris.
Laemanctus serratus, also known commonly as the serrated casquehead iguana, is a species of lizard in the family Corytophanidae. The species is native to southeastern Mexico and Central America. There are two recognized subspecies.
Sceloporus mikeprestoni, Preston's torquate lizard, is a species of lizard in the family Phrynosomatidae. It is endemic to Mexico.
Xenosaurus newmanorum, Newman's knob-scaled lizard, is a lizard found in Mexico.
Xenosaurus penai, Pena's knob-scaled lizard, is a lizard found in Mexico.
Barisia imbricata, also known commonly as the imbricate alligator lizard, the transvolcanic alligator lizard, and el escorpión de transvolcánico in Mexican Spanish, is a species of medium-sized lizard in the family Anguidae. The species is endemic to Mexico.
