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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 ]
The term spur is sometimes used to describe the pelvic spur, vestigial limbs found in primitive snakes, such as boas and pythons and in the striped legless lizard. [3] [4] The spurs primarily serve as holdfasts during mating. As these form at the terminal end of the limb, they may properly be claws rather than true spurs.
In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function.. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
In basal snakes, such as the python, embryos in early development exhibit a hind limb bud that develops with some cartilage and a cartilaginous pelvic element, however this degenerates before hatching. [98] This presence of vestigial development suggests that some snakes are still undergoing hind limb reduction before they are eliminated. [99]
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.
They are also “limbless” with only males having “rudimentary” hind limbs that form “flap-like structures” near their tails. A Dibamus tropcentr, or Ninh Thuận blind skink, on a piece ...
[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.