What makes a lizard a lizard?

Answer 1

To begin with, lizards are reptiles. Like all reptiles, they share the following features:

• They are vertebrates.
• They have dry, scaly skin.
• They are cold-blooded, or 'ectothermic', meaning they cannot generate their own heat to maintain body temperature, but instead have a variable body temperature which reflects the animal's environment.
• They breathe using lungs (unlike fish or juvenile amphibians).

Lizards are lizards because they have more specific features in common:

• Lizards generally have four well-developed limbs with five toes each. This does not include legless lizards which move like snakes, and burrowing lizards, which have less well-developed limbs.
• Most lizards, unlike snakes, have movable eyelids.
• Lizards have a three-chambered heart.
• Lizards have a pineal body which is connected to a "third eye." The "third eye" is invisible in most species, but it is a light-sensitive transparent disk on top of the head which is believed to regulate a lizard's "biological clock".