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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]
An adult salamander generally resembles a small lizard, having a basal tetrapod body form with a cylindrical trunk, four limbs, and a long tail. Except in the family Salamandridae, the head, body, and tail have a number of vertical depressions in the surface which run from the mid-dorsal region to the ventral area and are known as costal ...
(D′) Tricuspid teeth of the posterior jaw at the back of the mouth. (D″) Unicuspid teeth of the anterior jaw at the front of the mouth. Scale bar = 1 mm (A–D) and 200 μm (D′,D″). [1] In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology.
Squamata (/ s k w æ ˈ m eɪ t ə /, Latin squamatus, 'scaly, having scales') is the largest order of reptiles, comprising lizards and snakes.With over 12,162 species, [3] it is also the second-largest order of extant (living) vertebrates, after the perciform fish.
As polyphyodonts, geckos can replace each of their 100 teeth every 3 to 4 months. [43] Next to the full grown tooth there is a small replacement tooth developing from the odontogenic stem cell in the dental lamina. [44] The formation of the teeth is pleurodont; they are
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This differs from the condition found in most lizards (except acrodontans), which have pleurodont teeth which are attached to the shelf on the inward-facing side of the jaw, and are replaced throughout life. The teeth of the tuatara have no roots, though the teeth of some other rhynchocephalians possess roots. [23]
Some lizards, particularly iguanas, have retained a photosensory organ on the top of their heads called the parietal eye, a basal ("primitive") feature also present in the tuatara. This "eye" has only a rudimentary retina and lens and cannot form images, but is sensitive to changes in light and dark and can detect movement.