Reptiles are a class of cold-blooded vertebrate animals, including snakes, lizards, tortoises, tuataras, crocodilians, and dinosaurs. Birds may also arguably count. They are all absurdly cute and lovable.
Reptiles evolved from amphibians during the Carboniferous period, and were the dominant life form for millions of years, until a major extinction event at the end of the Cretaceous period. The ability to lay their eggs on land, as well as stay out of water without "drying up" led to their success. This allowed birds and mammals to diversify, both of which evolved from reptiles. Today, however, almost a fifth of all reptiles are in danger of going extinct.
Some cranks, such as David Icke, believe in the existence of a race or reptilian humanoids, which have infiltrated human society for some arbitrary and nefarious purpose, such as taking over the planet (why remains unknown).
Many reptiles, such as green anoles, are kept by people as pets: Ken Livingstone is a notable example.
Most are good eating.
Lizards are quadrupeds. They are typically small, fast, and insectivorous. However, a few families are meat, fruit, or even flower eaters; the size of humans; and extremely slow. Snakes evolved from them. They, in turn, evolved from four-legged amphibians.
These are also quadrupeds. They are archosaurs, like birds, and are their closest living relatives.
Also quadrapedal. These include turtles, tortoises, and terrapins, and let's not get into what each of those words mean. They are distinguished from other reptiles by having a great big bony shell. Some of them swim while some of them walk on land. They are particularly delicious, although most of them are endangered so you probably shouldn't eat any.
Snakes have no legs (oddly enough, there doesn't appear to be a sciencey word for that). However, to confuse the issue, there are also some species of lizards that don't have legs. Snakes are believed to represent a large group of lizards that evolved leglessness in the late Jurassic or early Cretaceous, while most other legless lizards lost their legs more recently. Something in lizard genes must really, really hate legs.
Leglessness is not a great way to tell a snake from a lizard. You can recognise snakes with a quick examination because they lack external ears and eyelids. There are also anatomical differences in the mouth and the eyes. Snakes have a much more primitive eye than other forms of reptile.
Tuataras live in New Zealand. They look like lizards but have differences, like low metabolism. The Tuatara is a living fossil, as it has changed very little over time because it is a hardy creature, though only 2 species remain. They are known to live for 100 years.
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- ↑ NBC News: Turtles, snakes and lizards head toward extinction 15 February 2013