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The hemipenis is the intromittent organ of Squamata, [4] which is the second largest order of vertebrates with over 9,000 species distributed around the world. They differ from the intromittent organs of most other amniotes such as mammals, archosaurs and turtles that have a single genital tubercle, as squamates have the paired genitalia remaining separate. [5]
Snakes have a wide diversity of skin coloration patterns which are often related to behavior, such as the tendency to have to flee from predators. Snakes that are at a high risk of predation tend to be plain, or have longitudinal stripes, providing few reference points to predators, thus allowing the snake to escape without being noticed.
The skull of Python reticulatus.. The skull of a snake is a very complex structure, with numerous joints to allow the snake to swallow prey far larger than its head.. The typical snake skull has a solidly ossified braincase, with the separate frontal bones and the united parietal bones extending downward to the basisphenoid, which is large and extends forward into a rostrum extending to the ...
Snakes, like other reptiles, have skin covered in scales. [1] Snakes are entirely covered with scales or scutes of various shapes and sizes, known as snakeskin as a whole. A scale protects the body of the snake, aids it in locomotion, allows moisture to be retained within, alters the surface characteristics such as roughness to aid in ...
Snakes are thought to have evolved from either burrowing or aquatic lizards, perhaps during the Jurassic period, with the earliest known fossils dating to between 143 and 167 Ma ago. The diversity of modern snakes appeared during the Paleocene epoch ( c. 66 to 56 Ma ago, after the Cretaceous–Paleogene extinction event ).
The sexes are often difficult to distinguish based on external characteristics. Male queen snakes have relatively longer tails than females. Males have from 65 to 89 subcaudal scutes (average 76), with the tail from 23% to 34% of the snake's total length. Females have 54 to 87 subcaudals (average 69), with tails equal to 19% to 27% of total length.
The semi-aquatic black swamp snake, Seminatrix pygaea, which lives in an environment where periods of drought are very common, has shown that environmental factors have a negative effect on female snakes whose large size was selected to increase fecundity as these droughts create a unique scenario to test whether survivability or reproductive ...
The red-sided garter snakes have an upper row of well-defined red spots, and lower row with patches of red color that smear on the dark area on either side of their back. [6] These snakes have multiple yellow stripes present on their body. Thamnophis sirtalis parietalis is sexually dimorphic, where females are usually larger than males. [4]