Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense it is a paraphyletic group encompassing all tetrapods, excluding the amniotes. All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura (frogs), Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems. Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.
The Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes lizards and snakes. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.
Amphisbaenia is a group of typically legless lizards, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As many species have a pink body and scales arranged in rings, they have a superficial resemblance to earthworms. While the genus Bipes retains forelimbs, all other genera are limbless. Phylogenetic studies suggest that they are nested within Lacertoidea, closed related to the lizard family Lacertidae. Amphisbaenians are widely distributed, occurring in North America, Europe, Africa, South America, Western Asia and the Caribbean. Most species are less than 6 inches (15 cm) long.
Dibamidae or blind skinks is a family of lizards characterized by their elongated cylindrical body and an apparent lack of limbs. Female dibamids are entirely limbless and the males retain small flap-like hind limbs, which they use to grip their partner during mating. They have a rigidly fused skull, lack pterygoid teeth and external ears. Their eyes are greatly reduced, and covered with a scale.
Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of tooth crowns, osteoderms, and a lateral fold in the skin of most taxa. The group is divided into two living subfamilies, the legless Anguinae, which contains slow worms and glass lizards, among others, found across the Northern Hemisphere, and Gerrhonotinae, which contains the alligator lizards, native to North and Central America. The family Diploglossidae was also formerly included. The family contains about 87 species in 8 genera.
Bipes is a genus of amphisbaenians found only in Mexico, the sole living member of the family Bipedidae. They are carnivorous, burrowing reptiles, but unlike other species of amphisbaenians, they possess two stubby forelimbs placed far forward on the body. They also retain an almost complete pectoral girdle. The shovel-like limbs are used to scrape away soil while burrowing, in a manner similar to a mole. Evidence for their occurrence in the United States is reviewed by Somma (1993).
The Amphisbaenidae are a family of amphisbaenians, a group of limbless vertebrates.
A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit.
A true toad is any member of the family Bufonidae, in the order Anura. This is the only family of anurans in which all members are known as toads, although some may be called frogs. The bufonids now comprise more than 35 genera, Bufo being the best known.
Many vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins. Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, whereas numerous reptile and amphibian lineages – and some eels and eel-like fish – independently lost their limbs. Larval amphibians, tadpoles, are also often limbless. No mammals or birds are limbless, but some feature partial limb-loss or limb reduction.
Indirana is a genus of frogs in the family Ranixalidae. These frogs are endemic to the Western Ghats of India. They are sometimes known under the common name Indian frogs, whereas members of their parent family are named "leaping frogs".
Necturus is a genus of aquatic salamanders in the family Proteidae. Species of the genus are native to the eastern United States and Canada. They are commonly known as waterdogs and mudpuppies. The common mudpuppy (N. maculosus) is probably the best-known species – as an amphibian with gill slits, it is often dissected in comparative anatomy classes. The common mudpuppy has the largest distribution of any fully aquatic salamander in North America.
Storeria dekayi, commonly known as De Kay's brown snake, De Kay's snake, and simply the brown snake, is a small non-venomous species of snake in the family Colubridae. The species is native to North America and Central America.
Rhineura floridana, known commonly as the Florida worm lizard, graveyard snake, or thunderworm, is a species of amphisbaenian in the family Rhineuridae. The species is the only extant member of the genus Rhineura, and is found primarily in Florida but has been recorded in Lanier County, Georgia. There are no subspecies that are recognized as being valid.
Rhineuridae is a family of amphisbaenians that includes one living genus and species, Rhineura floridana, as well as many extinct species belonging to both Rhineura and several extinct genera. The living R. floridana is found only in Georgia and Florida, but extinct species ranged across North America, some occurring as far west as Oregon. The family has a fossil record stretching back 60 million years to the Paleocene and was most diverse in the continental interior during the Eocene and Oligocene.
The Iberian worm lizard, Mediterranean worm lizard, or European worm lizard is a species of reptile in the family Blanidae of the clade Amphisbaenia. The Iberian worm lizard is locally known as cobra-cega (Portuguese), culebrilla ciega (Spanish), and colobreta cega (Catalan), all meaning "blind snake". Recent studies into the mitochondrial and nuclear genomic data of 47 isolated B. cinereus populations show rather large sequence divergence between two apparent clades, leading some researchers to call for a division of the Iberian worm lizard into two species. While little is known of B. cinereus in comparison with some other reptile species, new insight is growing about this primitive, ancestral reptile.
Blanus, also known as worm lizards, are a genus of amphisbaenians found in the Mediterranean region of Europe and North Africa. Like other amphisbaenians, Blanus species are specialized for a subterranean existence, with long, slender bodies, reduced limbs, and rudimentary eyes. Their skulls are powerfully constructed, allowing them to push through soil to create a burrow. Their jaws are well-developed, with large, recurved teeth and a pair of canine-like teeth in the upper jaw.
Oophaga is a genus of poison-dart frogs containing twelve species, many of which were formerly placed in the genus Dendrobates. The frogs are distributed in Central and South America, from Nicaragua south through the El Chocó to northern Ecuador. Their habitats vary with some species being arboreal while other being terrestrial, but the common feature is that their tadpoles are obligate egg feeders. Most species in this genus are seriously threatened and O. speciosa is already extinct.
Anniealexandria is an extinct genus of amphisbaenian lizard known by the type species Anniealexandria gansi from the earliest Eocene of Wyoming. Anniealexandria is the only known member of the family Bipedidae in the fossil record, which otherwise only includes the extant genus Bipes from Mexico. It was named in 2009 in honor of Annie Montague Alexander, founder of the University of California Museum of Paleontology. Remains of Anniealexandria are known only from a single fossil locality in the Bighorn Basin called Castle Gardens, but within the locality its fossils are common in the Willwood Formation, usually consisting of isolated jaw bones and vertebrae. Anniealexandria seems to have been a common component of a paleofauna that included fifteen other lizard species and existed in western North America during a period of global warming in the latest Paleocene and earliest Eocene.
