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Pelvic spurs (also known as vestigial legs) are external protrusions found around the cloaca in certain superfamilies of snakes belonging to the greater infraorder Alethinophidia. [1] These spurs are made up of the remnants of the femur bone, which is then covered by a corneal spur, or claw-like structure. [ 1 ]
Vestigial features may take various forms; for example, they may be patterns of behavior, anatomical structures, or biochemical processes. Like most other physical features, however functional, vestigial features in a given species may successively appear, develop, and persist or disappear at various stages within the life cycle of the organism ...
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 ...
Large, well-developed limbs increase drag on swimming animals, so the limbs of Eupodophis and other early snakes may have become vestigial to save energy and make movement more efficient. No vestigial limbs whatsoever are present in the modern species, which lack transitional species remnants. What few species have them protrude as tiny spurs.
Arrows show the vestigial structure called Darwin's tubercle. In the context of human evolution, vestigiality involves those traits occurring in humans that have lost all or most of their original function through evolution. Although structures called vestigial often appear functionless, they may retain lesser functions or develop minor new ones.
The Cretaceous snake Eupodophis had hind legs (circled). Developmental biology can identify homologous structures that arose from the same tissue in embryogenesis . For example, adult snakes have no legs, but their early embryos have limb-buds for hind legs, which are soon lost as the embryos develop.
Evidence for common descent comes from the existence of vestigial structures. [72] These rudimentary structures are often homologous to structures that correspond in related or ancestral species. A wide range of structures exist such as mutated and non-functioning genes, parts of a flower, muscles, organs, and even behaviors.
[10]: 11 [11] Pythons and boas—primitive groups among modern snakes—have vestigial hind limbs: tiny, clawed digits known as anal spurs, which are used to grasp during mating. [ 10 ] : 11 [ 12 ] The Leptotyphlopidae and Typhlopidae groups also possess remnants of the pelvic girdle, sometimes appearing as horny projections when visible.