Osteometrics of South-Central Andean wild camelids: New standards

Abstract

The osteometry of Neotropical camelids has drawn increasing attention over the last years given its potential to segregate species. Here we present two new osteometric standards for appendicular bones of wild camelids from the South-Central Andes (>3500 m.a.s.l.): a vicuña (Vicugna vicugna) and a guanaco (Lama guanicoe). The vicuña is from Antofagasta de la Sierra, near the margins of its present southern range. The Andean guanaco is from Sierra del Aconquija, also in NW Argentina, where this species is poorly documented. These new standards are generally consistent with other available ones. While vicuñas and guanacos do not generally overlap in size, they do with their domestic counterparts: alpacas and llamas, respectively. The new measured guanaco individual is among the smallest known ones, and compares to other specimens from NW Argentina. The measured vicuña and guanaco front first phalanx, one of the most diagnostic elements, varies mainly in the breadth dimension of the articular surface and not so much in its width. The forelimb first phalanges of both camelids are about the same length, as are the rear ones and the second phalanges, unlike other studies have reported. Yet, the guanaco first phalanges are much more robust in their diaphysis. Thus, bone gracility, and not just gross maximum linear size, may be a distinctive trait in some cases. Some measures are more powerful than others to discriminate taxonomy, as has often been emphasized, although this should be used with caution until size and shape variation is further recognized. Variation recognition in wild camelid osteometry is crucial to help understand its whole range and to link it to specific conditions.