Pelvic spur

External view of anal spurs on a male, albino burmese python

Skeleton of a Boelens python showing the bones inside the anal spurs

Pelvic spurs are the externally visible portion of the vestigial remnants of legs found on each side of the vent in primitive snakes, such as boas and pythons.^[1] The remnants of a pelvis and femur, which have no connection with the spine, simply "float" in the muscle mass.^[1] The femur protrudes from the snake's body and is covered by a corneal spur, which resembles a spur or claw.^[1] Males' spurs are generally longer and more pointed than females', and are used for clasping and tickling during courtship and mating,^[2] as well as combat with other males in some species.^[3]

References

1. ↑ 1.0 1.1 1.2 Pough et al. 1992. Herpetology: Third Edition. Pearson Prentice Hall:Pearson Education, Inc., 2002.
2. ↑ Courtship and Pelvic Spur Use in the Burmese Python, Python molurus bivittatus. James C. Gillingham and Jeffrey A. Chambers. Copeia, Vol. 1982, No. 1 (Feb. 23, 1982), pp. 193-196. http://www.jstor.org/stable/1444292
3. ↑ Combat Bouts with Spur Use in the Madagascan Boa (Sanzinia madagascariensis). Charles C. Carpenter, James B. Murphy and Lyndon A. Mitchell. Herpetologica, Vol. 34, No. 2 (Jun., 1978), pp. 207-212. http://www.jstor.org/stable/3891678