Lepidosauria
Encyclopedia
The Lepidosauria are reptile
s with overlapping scales. This subclass includes Squamata
and Sphenodontidae. It is a monophyletic group and therefore contains all descendents of a common ancestor. The squamata includes snake
s, lizard
s, tuatara
s, and amphisbaenia
. Lepidosauria is the sister taxon to Archosauria, which includes Aves and Crocodilia
. The only surviving tuataras are the family Sphenodontidae, genus Sphenodon. Lizards and snakes are the most speciose group of Lepidosaurs and combined contain about 7,970 species. However, the tuatara, which is found in New Zealand, has only two remaining species. There are noticeable distinguishing morphological differences between lizards, tuataras, and snakes.
instead of a single penis with erectile tissue that is found in crocodilians, birds, mammals, and turtles. The hemipenis can be found in the base of the tail. The tuatara has not fully evolved the hemipenis, but instead has shallow paired outpocketings of the posterior wall of the cloaca
that have been determined to be precursors to the hemipenis.
Second, most Lepidosaurs have the ability to autotomize their tails. However, this trait has been lost on some recent species. In lizards, fracture planes are present within the vertebrae of the tail that allow for its removal. Some lizards have multiple fracture planes, while others just have one single fracture plane. The regrowth of the tail is not always complete and is made of a solid rod of cartilage rather than individual vertebrae. In snakes, the tail separates between vertebrae and some do not experience regrowth.
Third, the scales in lepidosaurs are horny (keratinized) structures of the epidermis
, allowing them to be shed collectively, contrary to the scute
s seen in other reptiles. This is done in different cycles, depending on the species. However, lizards generally shed in flakes while snakes shed in one piece. Unlike scutes, the ledpidosaur scales will often overlap like roof tiles.
The group Squamata includes snakes, lizards, and amphisbaenians. Squamata can be characterized by the reduction or loss of limbs. Snakes, some lizards, and most amphisbaenians have evolved the complete loss of their limbs. The skin of all squamates is covered in scale
s. The upper jaw of Squamates is movable on the cranium, a configuration called kinesis. This is made possible by a loose connection between the quadrate and its neighboring bones. Without this, snakes would not be able consume prey that are much larger than themselves. However, the tuatara
does not share this characteristic with the other Lepidosauria. Amphisbaenians are mostly legless like snakes, but are generally much smaller. Three species of amphisbaenians have kept reduced front limbs and these species are known for actively burrowing in the ground.
Sphenodontidae includes tuatara and their extinct relatives and can presently only be found on small islands off New Zealand
. The tuatara has amphicoelous vertebrae, which means the vertebrae are hollowed out at both ends. The tuatara also have the ability to autotomize their tails. A well-developed median or pineal eye is present on the top of the head (parietal region) of the tuatara and their teeth are considered to be relatively large.
period. There were tertiary fossil snakes that became extinct by the end of the Eocene period. The first colubrid
also appeared in the Eocene period. Lizards first appeared in the middle Jurassic period, and this is when the scincomorph and the anguimorph lizards were first seen. The Gekko
tans first appear in the late Jurassic period and the iguania
ns first appear in the late Cretaceous period. The lizards of the Cretaceous period represent extinct genera and species. The majority of amphisbaenians first appeared during the early Cenozoic period. The Sphenodontidae fossil record first appears in the Lower Triassic period, making it the earliest found fossil record of the Lepidosauria. The tuatara can now only be found on small islands off the New Zealand coast. However, fossil records show that it once lived on the main land New Zealand and was distributed globally.
s: the Iguania
and the Scleroglossa
. Snakes and amphisbaenians belong within the clade Scleroglossa. The analysis of teeth results in Iguania being made up of the sister taxa Chamaeleonidae and Agamidae
. Snakes are actually a branch within the lizard group. In fact, some lizards, such as the Varanids, are more closely related to snakes that they are to other lizards. Varanids, which are semi-aquatic, large-bodied carnivorous lizards that reside in Australia.
Snakes currently have about 3070 extant species that are grouped into the scolecophidians and the alethinophidians. The scolecophidians are made up of about 370 species and are represented by small snakes with a limited gape size. The alethinophidians are made up of about 2,700 species and are represented by the more common snakes. As snakes evolved, their gape size increased from the narrowness of the scolecophidians. This allowed for the digestion
of larger prey. There are about 2,500 species of poisonous snakes that all belong to the Caenophidia.
The amphisbaenians are mostly limbless, with the exception of three species that kept reduced forms of front limbs. Morphological data shows that species with front limbs form a sister group to those that are limbless. This means that the amphisbaenians’ loss of limbs occurred only once.
The Tuataras originated in the Triassic period and were distributed world wide. All species went extinct in the late Cretaceous, except for the Tuatara that now lives in New Zealand. This extinction correlated with the appearance of mammals. The current Tuatara’s bone structure has evolved slightly from the species that existed in the Triassic period. Now, wild populations of the Tuatara can be found on thirty-two islands in addition to three islands in which populations have formed due to migration.
s, omnivore
s, insectivore
s, and carnivore
s. The herbivores consist of iguanines, some agamids, and some skink
s. Most lizards species and some snake species are insectivores. The remaining snake species, tuataras, and amphisbaenians are carnivores. Some snake species are generalist and eat a narrow range of prey. For example, Salvadora
eat only lizards. The remaining lizards are omnivores and can consume plants or insects.
Viperines can sense their prey’s infrared radiation through bare nerve endings on the skin of their heads. Also, viperines and some boids have thermal
receptors that allow them to target their prey’s heat. Many snakes are able to obtain their prey through constriction
. This is done by first biting the prey, then coiling their body around the prey. The snake then tightens its grip as the prey struggles which leads to suffocation. Some snakes have fangs that produce venom
ous bites. This allows the snake to consume an already dead or unconscious prey. Also, some venoms include a proteolytic component that aids in digestion. Chameleon
s grasp their prey with a projectile tongue. This is made possible by a hyoid mechanism, which is the contraction of the hyoid muscle that drives the tip of the tongue outwards.
The major predators of reptiles are other reptiles. Smaller reptiles are preyed upon by larger reptiles. Also, reptile eggs are consumed by other reptiles. Furthermore, birds are a predator of reptiles. Raptors, wading birds, roadrunners, are all examples of birds that consume reptiles. Mammals are also known to consume reptiles.
The geographic ranges of snakes and lizards are vast and cover all but the most extreme cold parts of the globe. Amphisbaenians exist in Florida
, mainland Mexico
including Baja California
, Mediterranean region, Middle East
, North Africa
, sub-Saharan Africa
, South America
, and the Caribbean
. The tuatara is confined to only a few rocky islands of New Zealand. It digs burrows to live in and preys mostly on insects.
. The tuatara lays eggs that are usually about one inch in length. These eggs take about fourteen months to incubate.
While in the egg, the Squamata embryo develops an egg tooth
on the premaxillary that helps the animal emerge from the egg. A reptile will increase three to twentyfold in length from hatching to adulthood. There are three main life history events that Lepidosaurs reach: hatching/birth, sexual maturity, and reproductive senility.
Most Lepidosaurs rely on camouflage
as one of their main defenses. Some species have evolved to blend in with their ecosystem, while others are able change their skin color to blend in with their current surroundings. The ability to autotomize the tail is another defense that is common among Lepidosaurs. Other species, such as the Echinosauria, have evolved the defense of feigning death.
Snakes are commonly feared throughout the world. There have actually been advertised rattlesnake
roundups in North America
. Data shows that between 1959 and 1986 an average of 5,563 rattlesnakes were killed per year in Sweetwater, Texas
, due to rattlesnake roundups, and these roundups have led to documented declines and local extirpations of rattlesnake populations, especially Eastern Diamondbacks
in Georgia.
Habitat destruction is the leading negative impact of humans on reptiles. Humans continue to develop land that is important habitat for the Lepidosaurs. The clear-cutting of land has also led to habitat reduction. Some snakes and lizards migrate toward human dwelling because there is an abundance of rodent and insect prey. However, these reptiles are seen as pests and are often exterminated
.
People have introduced species to the Lepidosaurs’ natural habitats that have increased predation on the reptiles. For example, mongooses were introduced to Jamaica
from India
to control the rat infestation in sugar cane fields. As a result, the mongoose
s fed on the lizard population of Jamaica, which has led to the elimination and decrease of many lizard species.
Actions can be taken by humans to help endangered reptiles. Some species are unable to be bred in captivity, but others have thrived. There is also the option of animal refuges. This concept is helpful to contain the reptiles and keep them from human dwellings. However, environmental fluctuations and predatorial attacks still occur in refuges.
Unfortunately, reptile skins are still being sold. Accessories such as shoes, boots, purses, belts, buttons, wallets, and lamp shades are all made out of reptile skin. In the year 1986, the World Resource Institute totaled that 10.5 million reptile skins were traded legally. This total does not even include the illegal trades of that year. Horned lizards are popular for being harvested and stuffed. Humans must make a conscious effort to preserve the remaining species of reptiles.
Climate change
has led to the need for conservation
efforts to protect the existence of the Tuatara. This is because it is not possible for this species to migrate to cooler climates. Conservationists are beginning to consider the possibility of translocating them to islands with cooler climates. The range of the Tuatara has already been minimized by the introduction of cats, rats, dogs, and mustelids. The eradication of the mammal
s from the islands where the Tuatara still survives has helped the species increase its population. An experiment observing the Tuatara population after the removal of the Polynesian Rat
showed that the Tuatara expressed an island specific increase of population after rat’s removal. However, it may be difficult to keep these small mammals from reinhabiting these islands.
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s with overlapping scales. This subclass includes Squamata
Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...
and Sphenodontidae. It is a monophyletic group and therefore contains all descendents of a common ancestor. The squamata includes snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s, lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s, tuatara
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
s, and amphisbaenia
Amphisbaenia
The Amphisbaenia are a usually legless suborder of squamates closely related to lizards and snakes. As many species possess a pink body coloration and scales arranged in rings, they have a superficial resemblance to earthworms. They are very poorly understood, due to their burrowing lifestyle...
. Lepidosauria is the sister taxon to Archosauria, which includes Aves and Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
. The only surviving tuataras are the family Sphenodontidae, genus Sphenodon. Lizards and snakes are the most speciose group of Lepidosaurs and combined contain about 7,970 species. However, the tuatara, which is found in New Zealand, has only two remaining species. There are noticeable distinguishing morphological differences between lizards, tuataras, and snakes.
Diagnosis
The reptiles in the subclass Lepidosauria can be distinguished from other reptiles by a variety of characteristics. First, the males have evolved a hemipenisHemipenis
A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...
instead of a single penis with erectile tissue that is found in crocodilians, birds, mammals, and turtles. The hemipenis can be found in the base of the tail. The tuatara has not fully evolved the hemipenis, but instead has shallow paired outpocketings of the posterior wall of the cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
that have been determined to be precursors to the hemipenis.
Second, most Lepidosaurs have the ability to autotomize their tails. However, this trait has been lost on some recent species. In lizards, fracture planes are present within the vertebrae of the tail that allow for its removal. Some lizards have multiple fracture planes, while others just have one single fracture plane. The regrowth of the tail is not always complete and is made of a solid rod of cartilage rather than individual vertebrae. In snakes, the tail separates between vertebrae and some do not experience regrowth.
Third, the scales in lepidosaurs are horny (keratinized) structures of the epidermis
Epidermis (zoology)
The Epidermis is an epithelium that covers the body of an eumetazoan . Eumetazoa have a cavity lined with a similar epithelium, the gastrodermis, which forms a boundary with the epidermis at the mouth.Sponges have no epithelium, and therefore no epidermis or gastrodermis...
, allowing them to be shed collectively, contrary to the scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s seen in other reptiles. This is done in different cycles, depending on the species. However, lizards generally shed in flakes while snakes shed in one piece. Unlike scutes, the ledpidosaur scales will often overlap like roof tiles.
General Description
Extant reptiles are divided into two clades: the Anapsida and the Diapsida. These clades are named for their number of temporal fenestrations in the skull. The Anapsida lack any temporal fenestration, but the Diapsida have a pair of temporal fenestrations on each side of the skull. The Anapsida are represented only by turtles and their extinct relatives. Diapsida is composed Lepidosauria and their sister taxa Archosauria. The subclass Lepidosauria is then split into Squamata and Sphenodontidae.The group Squamata includes snakes, lizards, and amphisbaenians. Squamata can be characterized by the reduction or loss of limbs. Snakes, some lizards, and most amphisbaenians have evolved the complete loss of their limbs. The skin of all squamates is covered in scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s. The upper jaw of Squamates is movable on the cranium, a configuration called kinesis. This is made possible by a loose connection between the quadrate and its neighboring bones. Without this, snakes would not be able consume prey that are much larger than themselves. However, the tuatara
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
does not share this characteristic with the other Lepidosauria. Amphisbaenians are mostly legless like snakes, but are generally much smaller. Three species of amphisbaenians have kept reduced front limbs and these species are known for actively burrowing in the ground.
Sphenodontidae includes tuatara and their extinct relatives and can presently only be found on small islands off New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. The tuatara has amphicoelous vertebrae, which means the vertebrae are hollowed out at both ends. The tuatara also have the ability to autotomize their tails. A well-developed median or pineal eye is present on the top of the head (parietal region) of the tuatara and their teeth are considered to be relatively large.
Fossil Record
Snakes do not have an extensive fossil record, but the oldest known snake fossil is from between early and late CretaceousCretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period. There were tertiary fossil snakes that became extinct by the end of the Eocene period. The first colubrid
Colubrid
A colubrid is a member of the snake family Colubridae. This broad classification of snakes includes about two-thirds of all snake species on earth. The earliest species of the snake family date back to the Oligocene epoch. With 304 genera and 1,938 species, Colubridae is the largest snake family...
also appeared in the Eocene period. Lizards first appeared in the middle Jurassic period, and this is when the scincomorph and the anguimorph lizards were first seen. The Gekko
Gekko
Gekko is a genus of colorful and diverse Southeast Asian geckos commonly known as true geckos or calling geckos. Although species such as the Tokay Gecko are very widespread and common, some species in the same genus have a very small range and are considered rare or endangered.-External links:* ...
tans first appear in the late Jurassic period and the iguania
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...
ns first appear in the late Cretaceous period. The lizards of the Cretaceous period represent extinct genera and species. The majority of amphisbaenians first appeared during the early Cenozoic period. The Sphenodontidae fossil record first appears in the Lower Triassic period, making it the earliest found fossil record of the Lepidosauria. The tuatara can now only be found on small islands off the New Zealand coast. However, fossil records show that it once lived on the main land New Zealand and was distributed globally.
Evolution
Lizards are originally split into two cladeClade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s: the Iguania
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...
and the Scleroglossa
Scleroglossa
Scleroglossa is the previously recognized suborder of Squamata that contains the geckos, anguids, worm lizards, monitor lizards, such as helodermatids, skinks and snakes. The name is derived from the Greek, skleros, meaning hard and glossa, meaning tongue.Traditionally, Squamata has been divided...
. Snakes and amphisbaenians belong within the clade Scleroglossa. The analysis of teeth results in Iguania being made up of the sister taxa Chamaeleonidae and Agamidae
Agamidae
Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have...
. Snakes are actually a branch within the lizard group. In fact, some lizards, such as the Varanids, are more closely related to snakes that they are to other lizards. Varanids, which are semi-aquatic, large-bodied carnivorous lizards that reside in Australia.
Snakes currently have about 3070 extant species that are grouped into the scolecophidians and the alethinophidians. The scolecophidians are made up of about 370 species and are represented by small snakes with a limited gape size. The alethinophidians are made up of about 2,700 species and are represented by the more common snakes. As snakes evolved, their gape size increased from the narrowness of the scolecophidians. This allowed for the digestion
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
of larger prey. There are about 2,500 species of poisonous snakes that all belong to the Caenophidia.
The amphisbaenians are mostly limbless, with the exception of three species that kept reduced forms of front limbs. Morphological data shows that species with front limbs form a sister group to those that are limbless. This means that the amphisbaenians’ loss of limbs occurred only once.
The Tuataras originated in the Triassic period and were distributed world wide. All species went extinct in the late Cretaceous, except for the Tuatara that now lives in New Zealand. This extinction correlated with the appearance of mammals. The current Tuatara’s bone structure has evolved slightly from the species that existed in the Triassic period. Now, wild populations of the Tuatara can be found on thirty-two islands in addition to three islands in which populations have formed due to migration.
Ecology
Within the subclass Lepidosauria there are herbivoreHerbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s, omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s, insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
s, and carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s. The herbivores consist of iguanines, some agamids, and some skink
Skink
Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...
s. Most lizards species and some snake species are insectivores. The remaining snake species, tuataras, and amphisbaenians are carnivores. Some snake species are generalist and eat a narrow range of prey. For example, Salvadora
Patchnose snake
Salvadora is a genus of colubrid snakes commonly called patchnose snakes or patch-nosed snakes. They are characterized by having a distinctive scale on the tip of their snout.-Species:*Baird's Patchnose Snake, Salvadora bairdi Jan, 1860...
eat only lizards. The remaining lizards are omnivores and can consume plants or insects.
Viperines can sense their prey’s infrared radiation through bare nerve endings on the skin of their heads. Also, viperines and some boids have thermal
Thermal
A thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection. The sun warms the ground, which in turn warms the air directly above it...
receptors that allow them to target their prey’s heat. Many snakes are able to obtain their prey through constriction
Constriction
Constriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...
. This is done by first biting the prey, then coiling their body around the prey. The snake then tightens its grip as the prey struggles which leads to suffocation. Some snakes have fangs that produce venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous bites. This allows the snake to consume an already dead or unconscious prey. Also, some venoms include a proteolytic component that aids in digestion. Chameleon
Chameleon
Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...
s grasp their prey with a projectile tongue. This is made possible by a hyoid mechanism, which is the contraction of the hyoid muscle that drives the tip of the tongue outwards.
The major predators of reptiles are other reptiles. Smaller reptiles are preyed upon by larger reptiles. Also, reptile eggs are consumed by other reptiles. Furthermore, birds are a predator of reptiles. Raptors, wading birds, roadrunners, are all examples of birds that consume reptiles. Mammals are also known to consume reptiles.
The geographic ranges of snakes and lizards are vast and cover all but the most extreme cold parts of the globe. Amphisbaenians exist in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, mainland Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
including Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, Mediterranean region, Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
, sub-Saharan Africa
Sub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...
, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, and the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
. The tuatara is confined to only a few rocky islands of New Zealand. It digs burrows to live in and preys mostly on insects.
Life History and Behavior
Squamates are represented by viviparous, ovoviviparous, and oviparous species. Viviparous means that the female gives birth to live young. Ovoviviparous means that the egg will develop inside of the female’s body. Oviparous means that the female lays eggs. A few species within Squamata have the ability to reproduce asexuallyAsexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
. The tuatara lays eggs that are usually about one inch in length. These eggs take about fourteen months to incubate.
While in the egg, the Squamata embryo develops an egg tooth
Egg tooth
In some egg-laying animals, the egg tooth is a small, sharp, cranial protuberance used by offspring to break or tear through the egg's surface during hatching...
on the premaxillary that helps the animal emerge from the egg. A reptile will increase three to twentyfold in length from hatching to adulthood. There are three main life history events that Lepidosaurs reach: hatching/birth, sexual maturity, and reproductive senility.
Most Lepidosaurs rely on camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
as one of their main defenses. Some species have evolved to blend in with their ecosystem, while others are able change their skin color to blend in with their current surroundings. The ability to autotomize the tail is another defense that is common among Lepidosaurs. Other species, such as the Echinosauria, have evolved the defense of feigning death.
Conservation
Rattlesnake
Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...
roundups in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Data shows that between 1959 and 1986 an average of 5,563 rattlesnakes were killed per year in Sweetwater, Texas
Sweetwater, Texas
Sweetwater is the county seat of Nolan County, Texas, United States. The population was 11,415 at the 2000 census.-History:Sweetwater received a U.S. post office in 1879. The Texas and Pacific Railway started service in 1881, with the first train arriving on March 12 of that year, beginning...
, due to rattlesnake roundups, and these roundups have led to documented declines and local extirpations of rattlesnake populations, especially Eastern Diamondbacks
Crotalus adamanteus
Crotalus adamanteus is a venomous pit viper species found in the southeastern United States. It is the heaviest venomous snake in the Americas and the largest rattlesnake. It featured prominently in the American Revolution, specifically as the symbol of what many consider to be the first flag of...
in Georgia.
Habitat destruction is the leading negative impact of humans on reptiles. Humans continue to develop land that is important habitat for the Lepidosaurs. The clear-cutting of land has also led to habitat reduction. Some snakes and lizards migrate toward human dwelling because there is an abundance of rodent and insect prey. However, these reptiles are seen as pests and are often exterminated
Pest control
Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy.-History:...
.
People have introduced species to the Lepidosaurs’ natural habitats that have increased predation on the reptiles. For example, mongooses were introduced to Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...
from India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
to control the rat infestation in sugar cane fields. As a result, the mongoose
Mongoose
Mongoose are a family of 33 living species of small carnivorans from southern Eurasia and mainland Africa. Four additional species from Madagascar in the subfamily Galidiinae, which were previously classified in this family, are also referred to as "mongooses" or "mongoose-like"...
s fed on the lizard population of Jamaica, which has led to the elimination and decrease of many lizard species.
Actions can be taken by humans to help endangered reptiles. Some species are unable to be bred in captivity, but others have thrived. There is also the option of animal refuges. This concept is helpful to contain the reptiles and keep them from human dwellings. However, environmental fluctuations and predatorial attacks still occur in refuges.
Unfortunately, reptile skins are still being sold. Accessories such as shoes, boots, purses, belts, buttons, wallets, and lamp shades are all made out of reptile skin. In the year 1986, the World Resource Institute totaled that 10.5 million reptile skins were traded legally. This total does not even include the illegal trades of that year. Horned lizards are popular for being harvested and stuffed. Humans must make a conscious effort to preserve the remaining species of reptiles.
Climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
has led to the need for conservation
Wildlife management
Wildlife management attempts to balance the needs of wildlife with the needs of people using the best available science. Wildlife management can include game keeping, wildlife conservation and pest control...
efforts to protect the existence of the Tuatara. This is because it is not possible for this species to migrate to cooler climates. Conservationists are beginning to consider the possibility of translocating them to islands with cooler climates. The range of the Tuatara has already been minimized by the introduction of cats, rats, dogs, and mustelids. The eradication of the mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s from the islands where the Tuatara still survives has helped the species increase its population. An experiment observing the Tuatara population after the removal of the Polynesian Rat
Polynesian Rat
The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...
showed that the Tuatara expressed an island specific increase of population after rat’s removal. However, it may be difficult to keep these small mammals from reinhabiting these islands.