Fire-lizards average around 2 feet from nose to tail, although size varies with age and colouration (sex). The female fire-lizards can be gold or green in colour while the males are bronze, brown or blue. While both gold and green fire-lizards lay eggs, only the gold or queen fire-lizards devote enough time and energy to protecting their clutch from predators to allow the eggs to hatch. In size the golden queens are the largest followed by the bronze, brown and blue males to the greens which are the smallest. They have six limbs: four legs and two wings.
Fire-lizards have two stomachs. One for digesting food, and one for processing a phosphine bearing rock referred to as firestone because, once 'digested', it permitted the dragons to produce flame. This was one of the main reasons that the original settlers of Pern used fire-lizard DNA to create the much larger dragons. The other reason was the intimate bond between a fire-lizard and its human partner. This empathic bond was developed into the much stronger telepathic link experienced by a human rider and their dragon. The bonding process is known as 'impression.'
Unlike the dragons which are capable of speaking telepathically with their human riders, fire-lizards are limited to conveying 'images' or emotions to their human friends. Consequently, the bond between humans and fire-lizards is weaker than with dragons. This allows people to impress more than one fire-lizard. The impression of nine fire-lizards from a single clutch by Menolly, is at the centre of Anne McCaffrey's novels Dragonsong and Dragonsinger.
Fire-lizards also have the ability to go between, or teleport. Theoretically fire-lizards should demonstrate telekinesis, but only dragons have demonstrated the intelligence required to move objects from one place to the next.
During the 'long interval' that historically preceded (and sets up) the first novel of Pern (Dragonflight, 1968), human contact with and knowledge of fire-lizards was lost. The practical rediscovery of the species and their abilities forms an important element of the second and third novels (Dragonquest, 1971; The White Dragon, 1978). This rediscovery culminates in the humans realizing that fire-lizards not only remember important events as individuals, but genetically transmit those memories, in good order, for generations--sufficiently so that their inherited memories of a volcanic disaster nearly 2,500 years earlier, focused through the white dragon Ruth, guide the modern Pernese to the lost, primary settlement of their human ancestors who colonised the planet. This bardic memory is an equivalent of the dragons' ability to time-travel, and drives the archaeological project that eventually recovers a working mainframe computer(AIVAS) and brings the primary narrative to its denouement.