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The scales may be ossified or tubercular, as in the case of lizards, or modified elaborately, as in the case of snakes. [1] The scales on the top of lizard and snake heads has also been called pileus, after the Latin word for cap, referring to the fact that these scales sit on the skull like a cap. [2]
Species identification using scales requires a fair degree of knowledge about snakes, their taxonomy, snake-scale nomenclature as well as familiarity with and access to scientific literature. Distinguishing by using scale diagrams whether a snake is venomous or not in the field cannot be done in the case of uncaught specimens.
Scales usually vary in size, the stouter, larger scales cover parts that are often exposed to physical stress (usually the feet, tail and head), while scales are small around the joints for flexibility. Most snakes have extra broad scales on the belly, each scale covering the belly from side to side.
Lizards and snakes share a movable quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls. [5] Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation. [6] As in other reptiles, the skin of lizards is covered in overlapping scales made of keratin. This ...
Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads (cranial kinesis).
Water collection has been shown in some rattlesnakes, though the nanostructure of the scales is thought to be more significant than the macrostructure (keel) of the scales. [6] In some viperines, most notably those of the genus Echis, the lateral scales are not only keeled, but the keels have minute serrations. The snakes use this in a warning ...
Most reptiles are viviparous, although oviparous reptiles do exist. Oviparous reptiles often display very little or no maternal behavior after the eggs have hatched, while viviparous reptiles typically exhibit more extensive maternal care. [1] Nile crocodiles however, are the exception to this.
Their kidneys (metanephros) and large intestines are also well-suited to water retention. Most mammals do not lay eggs, but corresponding structures develop inside the placenta. The ancestors of true amniotes, such as Casineria kiddi, which lived about 340 million years ago, evolved from amphibian reptiliomorphs and resembled small lizards.