Monday, June 22, 2009

Early Jurassic side-winder - but is it a snake?



Francois Durand's side-winding trace from the Clarens Formation. From Durand (2005.

Discussion about fossil side-winding traces over at Tet Zoo prompted me to get off my butt and actually put something up on this blog.
Its Francois Durand's apparent side-winding trace from the Clarens Formation of South Africa. Not much has been made of this and the only two references to it that I know of are rather obscure so I'm putting it up here to let people know about it.
It certainly looks like a track left by a modern sidewinding viper.



A modern side-winder

Francois made it fairly clear in his presentation of this fossil to the Geoscience Africa conferance back in 2004 that he thought it was made by an Early Jurassic viperid although he only hints at this in the two publications featuring this fossil that I know of. Such an occurence is strongly at odds with the known fossil record of snakes. Even the most primitive snakes don't show up until the Cretaceous, and advanced snakes like viperids don't start radiating until well in the Cenozoic, thus to have a Jurassic Viperid means that just about all tradtional family level clades of snakes have massive ghost lineages stretching back tens of millions of years. The fossil record can be spotty but it ain't THAT bad.
My take is that sidewinding habit may have evolved sporadically from time to time in all sorts of elongate limb-reduced tetrapods when the conditions warranted it. The whole discussion started over the possible sidewinding traces from a Permian, wet muddy, if not aquatic environment that I had a hand in describing.If correctly interpreted sidewinding need not be restrited to dry loose sand, wet sloppy mud might be just as capable of supporting it.
So what was elongate sidewinding tetrapod of the Clarens? We haven't a clue.

references

Durand, J.F. 2004. The origin of snakes. Geoscience Africa 2004. Abstract Volume, University of the Witwatersrand, Johannesburg, South Africa, pp. 187.

Durand, J.F. 2005. Major African contributions to Palaeozoic and Mesozoic
vertebrate palaeontology. Journal of African Earth Sciences 43: 53-82.

5 comments:

Mike Keesey said...

A lysorophian "Lazarus taxon" seems more likely than an early viperid, offhand.

Traumador said...

That is just neat, and weird.

Thanks for sharing the photos.

It is frustrating the way we can't tell behaviour from just bones, but then often can't directly link the few behaviour trace fossils we have to the bones...

John Scanlon FCD said...

Hi Adam,
I suppose you saw my long comment over at Tet Zoo on the Permian tracks; I'd be interested in any response addressing my inference about the unnatural direction of travel if that was actually a tetrapod.
As for Jurassic vipers - pfft. This mode of locomotion works well on mud, beach sand, and leaf litter, so it's not necessarily a specialisation of desert vipers; I've written up examples of elapids doing it, and there are non-caenophidian sidewinders in several families (boids, tropidophiids etc). Inventing ghost lineages for modern or Paleozoic groups is probably less helpful than looking for plausible trackmakers that actually lived in the Jurassic.

Raptor Lewis said...

If i'm not mistaken, the side-winder viper is a species of venomous snake, but, then, You'd think that a side-winder made those tracks yet there may not be a fossil of a similar animal in the vicinity. My Conclusion....trace fossils are frustrating! I mean....does anyone know exactly when snakes evolved?

Adam Yates said...

Hi John,

Yes I saw your comment over at Tet Zoo. An anguiliform fish? Interesting and I guess plausible. Though no such fish is currently described.
I must admit that the mechanics of sidewinding is something I really can't seem to wrap my head around. I just can't run that animation in my mind. Lance is the guy who looked at sidewinding in more depth and tried to apply to the permian trackways. The reconstruction does seem to be in error however since it shows two loops of the body on one track (never noticed this before).
Re. Durand's sidewinder, I agree completely, the question is what serpentiform vertebrate was around in the gondwanan deserts of the Early J? So far I don't think we have found any candidates at all.