Snakes are reptiles. They are part of the order Squamata. They don't have legs, voice, ears, and eyelids. Despite this, snakes are successful carnivores. There are at least 20 families,and about 500 genera and 3,400 species.
They have a long, slender body, and are very mobile in their own way. Most of them live in the tropics. Very few snake species live beyond the Tropic of Cancer or Tropic of Capricorn, and only one species, the common viper (Vipera berus) lives beyond the Arctic Circle. Their skin is covered with scales. They can see well enough, and they can taste scents with their tongues by flicking them in and out. They are very sensitive to vibrations in the ground.
Though they do not have a voice, they can hiss. Most snakes live on the ground, others live in the water, and a few live under the soil. Like all reptiles, snakes need the heat of the sun to control their body temperature. That is why most snakes are in the warm, humid tropical regions of the world.
They range in size from the tiny, 10.4 cm-long thread snake to the reticulated python of 6.95 meters (22.8 ft) in length. The fossil Titanoboa was 12.8 meters (42 ft) long.