I immediately brought the issue up to my herpetology professor here at my university. She had been taught that the pelvic spurs of snakes are related to vestigial legs, and she had never heard anything contrary to this idea. She managed to find a quick reference to pelvic spurs in my textbook, but the mention was brief and provided no analysis. Even though I would trust both of these sources, I also realize that they could be misinformed.
I began searching for reasons behind the conflict. It appears that there are two issues at hand here that make the connection between pelvic spurs and legs a bit fuzzy:
1.) Pelvic spurs are not connected to bones. Some use this argument to claim that pelvic spurs are not related to legs. However, I say this means nothing. Just because structures are not connected now, we cannot assume that they were not connected millions of years ago.
2.) Pelvic spurs have much greater mobility than other scales. If you have ever seen a snake move, you will recognize how the skin of the snake will stretch and bend as the snake winds, and the keratinous scales move along with it. The only thing that changes as the snake bends is the spacing between the scales. Pelvic spurs, on the other hand, are quite mobile, and the male will be able to make his pelvic spurs pivot, dig, and tap.
|Legless lizard. What a cutie.|
Found at http://lpfw.org/wp-content/uploads/2012/04/legless-lizard.jpg
I realized quickly that this is becoming one large mess that is going to be very difficult to sort out. I would suggest exactly what Hoser recommended in 1985, and that's that we first examine the structure of the legless lizard in more depth. Perhaps legs and pelvic spurs have nothing in common. However, I would also recommend that we look into the exact musculature that is used to move the pelvic spurs because perhaps this could be related to the same muscles used in legs.
I believe the most defining evidence found will come from development. If we can look at which genes contribute to the development of the pelvic spurs (and in which patterns these genes are activated), we may be able to determine if pelvic spurs arose from legs. After all, many genes and developmental patterns are shared among species that look nothing alike. Using the same genes (which Sean Carroll refers to as "tool kit genes" in Endless Forms Most Beautiful), many animals follow the same patterns to develop very different structures. I suggest that if the pattern is the same, perhaps the structures are related.
In conclusion, it appears that pelvic spurs are generally accepted as vestigial leg remnants among the herpetologist community. Although I now say I do not have the answers, I think the topic should be investigated rather than assumed.
Through all of this mess, one thing has been cleared up. In my first post regarding pelvic spurs, I questioned whether female pythons had pelvic spurs. In fact, according to Slip and Shine (1988), females have pelvic spurs, though they are less prominent than the males'.