A living relative of the dinosaurs' neighbours
The TUATARA of New Zealand looks like a lizard but is not one. It is the last surviving member of a group of reptiles that lived alongside the early dinosaurs, and it has a third eye on top of its head, called the parietal eye, which is covered by scales in adults but is sensitive to light. Tuatara grow very slowly and can live for more than a century.
Reptiles are cold-blooded, or more accurately ectothermic: they rely on sunshine and warm surfaces to heat their bodies rather than burning food for warmth. That is why a LIZARD basks on a rock in the morning, and why reptiles can go for long periods without eating. Our dinosaurs page covers their ancient relatives.
Dragons that do not need a father
The KOMODO dragon of Indonesia is the largest lizard in the world, up to about three metres long. Scientists once believed it killed prey mainly through bacteria in its mouth, but in 2009 researchers showed it has venom glands in its jaw. In 2006, female Komodo dragons at two British zoos laid eggs that hatched although they had never been near a male, a kind of reproduction called parthenogenesis.
A CHAMELEON changes colour mainly to signal to other chameleons and to warm up or cool down, rather than to match its background. In 2015 scientists found it does this by adjusting a layer of tiny crystals in its skin, which changes how light is reflected. Its eyes can swivel separately, so it can look in two directions at once.
Sticky feet and smelling with a tongue
A GECKO can run up glass and hang upside down from a ceiling. Its toes are covered with millions of microscopic hairs, and each splits into even finer tips, so close to the surface that weak forces between molecules hold the gecko on. Engineers have copied the idea to make reusable dry adhesives.
A SNAKE flicks its forked tongue to collect scent particles from the air and carries them to a special organ in the roof of its mouth. Because the tongue has two tips, the snake can tell which side a smell is stronger on. Snakes have no eyelids; a clear scale covers each eye. The ADDER is the only venomous snake native to Britain, and it is shy.
Crocodile or alligator, turtle or tortoise
An ALLIGATOR has a wide, rounded U-shaped snout, and when its mouth is shut its lower teeth are hidden. A CROCODILE has a narrower, pointed snout and a big tooth that shows on each side of the lower jaw even with its mouth closed. Wild alligators live only in the United States and China. In British usage, a TURTLE lives in the sea, a TORTOISE on land, and a TERRAPIN in fresh water.
The rest of the grid holds the snakes — the COBRA, PYTHON, BOA, VIPER, MAMBA and ANACONDA, the heaviest snake in the world — and the lizards: the IGUANA, the SKINK, the MONITOR, and the venomous GILA monster. Every one of them is a REPTILE, with dry, scaly skin.