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Introduction

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Selected reptile type

Nile crocodile (Crocodylus niloticus)

Crocodiles (family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant members of the order Crocodilia, which includes the alligators and caimans (family Alligatoridae), the gharial and false gharial (family Gavialidae) among other extinct taxa.

Although they appear similar, crocodiles, alligators and the gharial belong to separate biological families. The gharial, with its narrow snout, is easier to distinguish, while morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head, with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait is that the upper and lower jaws of the crocodiles are the same width, and the teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed; therefore, all teeth are visible, unlike an alligator, which possesses in the upper jaw small depressions into which the lower teeth fit. Also, when the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define the species' family. Crocodiles have more webbing on the toes of the hind feet and can better tolerate saltwater due to specialized salt glands for filtering out salt, which are present, but non-functioning, in alligators. Another trait that separates crocodiles from other crocodilians is their much higher levels of aggression.

Crocodile size, morphology, behaviour and ecology differ somewhat among species. However, they have many similarities in these areas as well. All crocodiles are semiaquatic and tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water and saltwater. They are carnivorous animals, feeding mostly on vertebrates such as fish, reptiles, birds and mammals, and sometimes on invertebrates such as molluscs and crustaceans, depending on species and age. All crocodiles are tropical species that, unlike alligators, are very sensitive to cold. They separated from other crocodilians during the Eocene epoch, about 55 million years ago. Many species are at the risk of extinction, some being classified as critically endangered. (Full article...)

Selected Crocodilia article

In Llanos, Venezuela

The spectacled caiman (Caiman crocodilus), also known as the white caiman, common caiman, and speckled caiman, is a crocodilian in the family Alligatoridae. It is brownish-, greenish-, or yellowish-gray colored and has a spectacle-like ridge between its eyes, which is where its common name come from. It grows to a length of 1.4–2.5 m (4 ft 7 in – 8 ft 2 in) and a weight of 7–40 kg (15–88 lb), with males being both longer and heavier than females. Its diet varies seasonally, commonly consisting of crabs, fish, small mammals, amphibians and snails. Breeding occurs from May to August and 14–40 eggs are laid in July and August. This crocodilian has a large range and population; it is native to much of Latin America, and has been introduced to the United States, Cuba, and Puerto Rico. (Full article...)

Selected lizard article

Ptychozoon kuhli

Ptychozoon was a genus of arboreal geckos, endemic to Southeast Asia, known commonly as flying geckos, gliding geckos, or parachute geckos. They all are now placed in the genus Gekko in the family Gekkonidae. The biogeographic history of the genus Ptychozoon was deeply nested within that of the genus Gekko, the center of diversity of which is within Southeast Asia. Since dispersing into Southeast Asian rainforests, Pytochozoon, like other forest-dwelling vertebrates, adapted to facilitate gliding. All species in the genus Ptychozoon are characterized by cryptic coloration and elaborate webs surrounding the neck, limbs, trunk, and tail. These membranes help to conceal the gecko against trees. When the gecko leaps into the air, the flaps are used to generate lift and allow the gecko to control its fall. It can glide up to 200 feet (61 meters). Also it does a swoop at the end of its glide to land softly. A similar adaptation is found in geckos of the genus Cosymbotus. There were thirteen described species in the genus Ptychozoon. (Full article...)

Selected turtle article

The western pond turtle (Actinemys marmorata), also known commonly as the Pacific pond turtle is a species of small to medium-sized turtle in the family Emydidae. The species is endemic to the western coast of the United States and Mexico, ranging from western Washington state to northern Baja California. It was formerly found in Canada (in British Columbia), but in May 2002, the Canadian Species at Risk Act listed the Pacific pond turtle as being extirpated. (Full article...)