San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide

Glossary of Reptile Terms


An inherited (genetically controlled) characteristic of an organism that helps it to survive and reproduce in the environment it inhabits. These are often interpreted as evolutionary changes in response to selection pressures present in that environment.
An animal that produces an embryo within a sac that contains amniotic fluid. Amniotes include turtles, lizards, snakes, tuataras, crocodilians, birds, and mammals.
A reproductive behavior in frogs where the male grasps the female from behind. This positions his vent near hers to assure fertilization.
The area on the sides and belly, behind or below the front legs. The "armpit" area.
Bipedal Locomotion
Literally, moving on two feet. Refers to running on the hind legs, which is seen in some very fast lizards, particularly on loose surfaces such as sand. Some tropical lizards can even run for short distances across the surface of water.
The shell covering the back (top) of a turtle, crab, or other animal.
Said of an animal which primarily eats other animals.
Referring to the tail.
Caudal Autonomy
A defensive feature found in many lizard and salamander species, where the tail vertebrae are easily broken, so that the tail will break off if it is grabbed by a predator. Also called tail separation.
In California and Baja California, the region between the Pacific coast and the ridge of the mountains. The desert side of the mountains is called "transmontane."
A body opening that serves both for excretion and for the reproductive organs.
A group of eggs that is laid in the same place at the same time (or nearly the same time), and will hatch at the same time.
A snake that kills its prey by grabbing the animal and throwing two or three coils around it. The force of constriction (squeezing) prevents the prey from breathing, and it usually dies within seconds. The snake can then relax its grip and swallow the animal head-first.
Costal grooves
A series of vertical grooves on the sides of salamanders, between the fore- and hindlimb.
Active during the evening and early morning hours.
Cryptic coloration
A pattern of colors that makes an animal hard to see. It may be a pattern that is similar to the background on which the animal lives, or one that seems to break up the animal's outline (also called "disruptive coloration")
Active during the day.
Referring to features on the back or along the spine of the animal.
An animal whose body temperature varies with the temperature of its surroundings (also called cold-blooded).
An animal that maintains its body temperature at a relatively constant level by physiological means regardless of the temperature of the environment (also called warm-blooded)
The period of time between mating and the birth of the young.
Said of females when they are carrying fertilized eggs.
Gravid Coloration
Bright markings found in gravid females in some species of lizards. See our fuller description of gravid coloration, with illustrating photos.
The kind of place where a plant or animal naturally lives.
Said of an animal which eats only plants.
The specimen of an animal (or plant) which is designated in the publication when the organism is named, as representing what is meant by the new name. The holotype specimen may or may not be the first ever collected, and may or may not be a good example of its kind. But it is the official designation: "THIS name refers to THIS animal." Often, other specimens are cited in the same publication, and are called "secondary types."
-idae or -id
Suffixes for the name of an animal family. For example, the dog family is Canidae, and members of the family can all be called "canids" even if they're not in the genus Canis, for which the family is named.
The area on the underside in front of the hind legs. The "groin" area.
Said of an animal which mostly eats insects
A ridge down the center of a scale. Very sharp keeling may make an animal appear quite rough. In general, an animal with keeled scales will appear less shiny and lustrous than one with unkeeled scales, as the keeling causes the reflected light to scatter.
As early stage in life, usually before sexual maturity is reached. In amphibians, larval stages are for feeding. The animal will metamorphosize into the adult stage.
Referring to the sides of the body. "Laterally compressed" means flattened in such a way that the thing is high but not very wide.
Live Birth
In reptiles, this is when the eggs hatch while still inside the female, and the young soon emerge alive. The young do not obtain nutrients from their mother while in the reproductive tract, as is the case with most mammals. A condition known as oviviviparous.
The developmental transition between larval and adult stages that can include extreme morphological transformations.
Active at night.
Reproduces by laying eggs.
Reproduces by eggs which remain in the mother's body until they are ready to hatch. When the young emerge, they are born live, with only a membrane to break out of.
Parotid Glands
Paired glands in the form of large bumps. In toads, these are located behind the eyes on the neck and secrete toxic substances used for defense.
Parietal Eye
A light-sensing organ on the top of the head, found in some lizards.
The shell covering the underside (bottom) of a turtle or other animal
Said of an animal that eats lizards.
A method of locomotion used by some snakes, for traveling across loose surfaces such as sand.
Sexual Dimorphism
Refers to a species where the males and females are different in appearance. This can be a difference in size, or in other visual features.
Snout-Vent Length
A standard measurement of body length. The measurement is from the tip of the nose (snout) to the anus (vent), and excludes the tail.
In salamanders, males will deposit a ball of sperm, or male reproductive cells, on the ground after courtship with the female. The female will use her cloaca to grasp the spermatophore to complete copulation.
The larval stage of frogs. Tadpoles will metamorphosize into adult frogs by losing their tail and gill slits, and developing fore- and hindlimbs.
Tail Separation
A defensive feature found in many lizard species, where the tail vertebrae are easily broken, so that the tail will break off if it is grabbed by a predator. Same as "caudal autonomy."
Type specimen
A specimen which is designated in the publication of a new name for an organism. See holotype
The cloaca of an animal; in reptiles this opening may also serve the reproductive organs. It is seen as a marker of where the body ends and the tail begins, which is hard to determine in some animals, such as snakes.
Referring to the underside of an animal, the "tummy" side.
Remaining in a species only in a much reduced or useless state. Vestigial body parts or organs are evidence of parts that the ancestors of an animal had, but that the modern animal no longer needs or uses. For example, the Rosy Boa bears vestigial traces of the legs of its lizard ancestors.
Tiny bumps on the skin surface. In geckos, villi on the toes allow them to cling to walls and ceilings.
Reproducing by giving birth to live young.