Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Sauria

The suborder Sauria contains the lizards, and not the crocodilians or the dinosaurs as suggested by our friend Webster 1913, below. Within this suborder are five infraorders, containing 19 families, which are at times further divided into subfamilies.1

General description

There are 4636 lizard species currently extant worldwide, in addition to those that may be discovered at some later date. They are found on six of the seven continents (the exception being Antarctica, for obvious reasons). They are generally small, cold-blooded, have scales covering their entire body and have two pairs of limbs. They may be nocturnal, diurnal or crepuscular, and must rely on their environment to heat their bodies. They have ears, unlike snakes, and always have small openings posterior to the eyes which lead to the auditory anatomy. All lizards produce young through eggs, and the normal reproductive strategy involves laying from two to dozens of eggs in a well-hidden burrow or mound. Some, on the other hand are ovoviviparous, meaning that while the embryos do develop in eggs, the eggs are retained inside the body of the female until such time as they hatch. These species give birth to live young, in a manner superficially similar to mammals. Most lizards are insectivorious, but there are top predators and herbivores in the suborder.

Some exceptional members

Many lizards are drab in their colouration, and are generally pretty unremarkable in appearance and behaviour (except, of course, to herpetologists and herpetoculturists). There are, however, some exceptional and fascinating members of this family which deserve special mention. Instead of trying to list them all here, I've chosen instead to mention a specific individual for each interesting behaviour or adaptation.

Caudal autotomy

Many lizards are capable of dropping their tail when threatened by a predator, which is a particularly good anti-predator defense. The five-lined skink (Eumeces fasciatus), found across North America, is a perfect example of such a species. It is a small, insectivorious species which, when threatened by a predator such as a bird, cat or dog, will drop its tail and scamper off to safety.

Camouflage and crypsis

The other common anti-predator defense used by lizards is crypsis, which is the tactic of remaining hidden or camouflaged so that the predator cannot see the prey. Almost all lizards are coloured and patterned in such a way as to blend in with their surroundings, but the chameleons take this strategy several steps further. They are capable of changing their colour and pattern using the chromatophores in their skin2. They also move along branches of trees by rocking back and forth, making them appear remarkably similar to a leaf moving in the wind. These two adapatations make them able predators and particularly difficult prey.

Other antipredator defenses

Some other lizards have adopted different antipredator defenses. Notable amongst these are the behaviours of the horned toad and some young skinks and monitors. The horned toad, when threatened, dramatically increases the pressure in the capillaries surrounding their eyes, causing them to burst and shoot streams of blood considerable distances. Young monitors, on the other hand, have a habit of defecating and urinating voluminously when threatened, and given their carnivorous and scavenging diet, this is not a pleasant experience for any animal in the immediate vicinity (imagine a stench similar to a skunks, but with a liquid which burns and sticks, and you've got their anti-predator defense figured out).

Venom

While the subfamily serpentes has large numbers of venomous species (cobra, viper, death adder, etc.), there are two lizard species which are venomous: the gila monster and the Mexican beaded lizard. These two species, rather than having fangs, produce their venom in their saliva glands and inject it into their prey as they chew. The venom is not particularly powerful, and not considered life threatening to humans, but is an evolutionary wonder.

Other biological warmongers

While not venomous, per se, the komodo dragon also has the ability to incapacitate prey using its saliva. The komodo has a large and diverse bacterial flora living in its mouth, and these bacteria cause all mammals to fall very ill, often fatally. They use the bacteria to incapacitate larger prey such as deer and small humans. The komodo will attack their prey, and if they can't kill it immediately, will innoculate the mammal with these bacteria. Days later, the prey will succumb to the sickness and die, and the komodo will then consume the carcass (yes, they will follow the animal for days waiting for them to collapse).

King Kong ain't got nothing on these guys

While many lizards are terrestrial or even subterranean, many make their living up in the forest canopy. The chameleon, already mentioned, has evolved feet which help it grip the branches of trees in a very controlled manner. The toes have fused together in both the fore- and hind-feet, giving the animal two pads instead of five toes. These pads grip branches strongly, giving the chameleon a very good ability to remain aloft even under high winds.

Another species, the monkey-tailed skink, has evolved a powerful, prehensile tail which is used to grip the branches and trunks of trees. These herbivorous lizards are quite large, and so use this tail to remain anchored to the tree while they extend their bodies in order to reach the leaves which they covet.

And the cult was born ...

Finally, the basilisks have one of the most amazing abilities in the entire subfamily. These Amazonian lizards have very long toes on their back feet, which are principally used to help the animal climb but also allow them to literally run across the surface of the water. By ]rearing up] on their hind legs and moving them like a windmill, basilisks can run considerable distances over the surface of a pond when fleeing from a predator. They use the large surface area of their hind feet and the surface tension of the water to accomplish this wonderous feat, earning them the common name Jesus lizard

Taxonomic information

What follows is a list of the families and subfamilies within the suborder Sauria. Next to each scientific name is the common name of the group and an estimate of the number of species.

1 With most things taxonomic, this classification is not unanimously supported in the academic community. Some classifications place both the birds and some dinosaurs within the Sauria. (Thanks go to Gorgonzola for pointing this out).
2 Note that recent research suggests that chameleons change their colouration most often to communicate with other members of the species, rather than as camouflage.
Constructed, in part, with help from the Reptile Database, http://http://www.embl-heidelberg.de/~uetz/LivingReptiles.html

Sau"ri*a (?), n. pl. [NL., from Gr. a liard.] Zool.

A division of Reptilia formerly established to include the Lacertilia, Crocodilia, Dinosauria, and other groups. By some writers the name is restricted to the Lacertilia.

 

© Webster 1913.

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