Why Do Reptiles Have Scales?: And Other Questions About Evolution and Classification
What is a reptile Reptiles were the first vertebrates to become fully adapted to life on dry land They are cold-blooded animals which means that their body temperature changes according to their surroundings A reptile’s skin is covered with scales made of keratin the same material as our hair and nails Reptiles cannot control their body temperature They bask in the Sun to warm up and move into the shade when they get too hot Ruling reptiles Reptiles evolved more than 300 million years ago from reptile-like amphibians Amphibians have moist skin and breed in water Reptiles developed tough scaly skin and eggs with tough shells so they could move away from the water and spread throughout the world They became so successful that giant reptiles including dinosaurs and pterosaurs ruled the Earth during the Mesozoic era Dinosaurs see box text included the largest animals ever to have walked the Earth 4
Winged lizards Pterosaurs were flying reptiles that lived alongside the dinosaurs They were the earliest vertebrates to develop powered flight Their wings were made up of skin and muscle and stretched from their ankles to their extra-long fourth finger With a wingspan of about 36 feet 11 m the pterosaur Quetzalcoatlus was one of the largest flying animals of all time Marine giants While dinosaurs ruled the land during the Mesozoic era other reptiles took to the water During the Cretaceous period marine monsters including the fearsome mosasaurs preyed on fish birds and other reptiles Mosasaurs stalked their prey until it was within striking distance of their massive jaws 5
Classification of reptiles The main groups of reptiles are turtles crocodilians snakes lizards and tuataras Snakes and legless lizards look similar but they are different Lizards have eyelids and ear openings unlike snakes and a lizard’s tail makes up two thirds of its length while a snake’s makes up just a third Turtles Vipers Turtles tortoises and terrapins are among the oldest of today’s reptiles They have hardly changed since they first appeared more than 220 million years ago Vipers are venomous snakes that are found in the Americas Africa Europe and Asia They include rattlesnakes and adders They have long hinged fangs Most give birth to live young Crocodilians Crocodilians include alligators crocodiles gharials and caimans They first appeared about 84 million years ago and are the closest living relatives of the birds Colubrids About two-thirds of all snakes belong to the colubrid family Most are not venomous They live on every continent except Antarctica 6 Elapid snakes Elapids are a family of agile venomous snakes which live in warm parts of the world They include the king cobra and some tree-dwelling and burrowing snakes Sea snakes These elapid snakes have adapted to life in salt water They have evolved paddle like tails and have a gland that gets rid of excess salt Some have the strongest venom of all snakes
Boas Pythons Pythons live in Africa and Asia They are non venomous constrictor snakes that lay eggs The reticulated python is the longest known snake Iguanas Boas are non-venomous constrictor snakes found in America Africa Europe Asia and some Pacific islands Females are usually larger than males and they give birth to live young Monitors Monitor lizards have long necks strong legs and powerful claws They include the Komodo dragon the largest lizard alive today Skinks Skinks are a very varied group of lizards Most have small legs and no obvious neck Some have lost their forelegs completely and look more like snakes Anguid lizards This group includes alligator lizards and several species of legless lizards including slow worms and glass lizards Some lay eggs and others give birth to live young wheat or oats Iguanas are plant-eating lizards that live in tropical regions They have good eyesight and are well camouflaged Marine iguanas are found only on the Galápagos Islands Chameleons Chameleons are lizards that are well known for their ability to change color Most live in trees Those species that live on the ground usually have brown skin for camouflage Geckos Thanks to their sticky feet geckos can walk up walls and hang from ceilings These lizards communicate with one another using chirping sounds Nocturnal geckos have excellent night vision Worm lizards Worm lizards are burrowers and have adapted to a life spent almost entirely underground Three of the four groups have lost all traces of legs Tuataras Tuataras appeared about 220 million years ago They were once widespread but today only two species remain on a few islands in New Zealand 7
