Sabretooths left footprints, too.

After reading my previous post, readers may think, OK, these early felid footprints look interesting but, did not sabretooths leave footprints too?. Obviously they did, but the fossil record of their tracks is very poor. This is unfortunate because not everyone agrees on the details of sabretooth locomotion, and some specialists have proposed that animals like  Smilodon, or the nimravid sabretooths, were plantigrade, walking on the soles of their feet like bears, rather than walking on digitigrade, cat-like feet. We would need several fossil tracksites similar to Salinas de Añana, but from different times and places, to help us solve these uncertainties. There are, anyway, a few sites that have yielded the footprints of sabretooths, and in one of these sites we have the uniquely lucky coincidence of finding both the footprints and the direct fossil remains of the animals themselves. That place has been known for many decades, and is one of the classic sites that helped define the Hemphillian, an age within the late Miocene of North America (formerly thought to be part of the Pliocene): Cofee Ranch, in Texas (see: Johnston, C. S. 1937. Tracks from the Pliocene of West Texas. Am. Midl. Nat., 18(1): 147-152).

At Cofee Ranch, the most complete skeleton known to date of the sabretooth Machairodus coloradensis was found not far from the footprint of a large cat-like animal. The well preserved footprint measures 13,2 by 11 cms, and is thus larger than most modern lion footprints. At that time, conical-toothed cats of the modern subfamily felinae were smallish animals, none of them larger than a lynx, and the only cat around that was large enough to leave such a huge footprint was Machairodus. The morphology of the Cofee Ranch cat print is quite modern, with paraxonic shape, retracted claws, and a reduced interdigital pad, and indicates a fully digitigrade posture. This morphology nicely fits what the known osteology of Machairodus and its relatives of the Homotherin tribe already told us – that these cats walked and ran much in the same way as our lions and tigers do. The detailed anatomy of Smilodon suggests so much as well, but the animal was much more robust and short-limbed than Machairodus, so a nice set of footprints from some Ice Age fossil site would not hurt. And the nimravid and barbourofelid sabertooths, with their primitive-looking feet are more difficult to interpret in terms of locomotion, so we must hope that more Miocene tracksites will be discovered in the future, including some sabretooth trackways. Meanwhile, functional anatomy will be our only guide to reconstruct their locomotion, and detailed, updated studies are urgently needed on that field too.

Posted on 18/07/2011, in Uncategorized. Bookmark the permalink. Leave a comment.

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