Researchers from the University of Oviedo have recovered the cranium of a bison that live during the Ice Age in Asturias at the cave of La Rexidora, in the municipality of Ribadesella. The sample, which has been dated to be betwee 30,000 to 40,000 years old, is one of the most complete craniums among those found in the Iberian Peninsula and it has been reconstructed at the laboratories of the area of Paleontology of the Department of Geology of the University of Oviedo.

The excavations conducted by Professors Diego Álvarez Lago and Alejandro García Álvarez in the dig site of Ribadesella have been funded by the University of Oviedo as part of its call for financial aid for emergent research groups. The project Estudios paleombientales de los episodios fríos del Pleistoceno Superior en la región cantábrica a partir del yacimiento de la cueva de La Rexidora (Cuerres, Ribadesella) has led to the beginning of the exacavation of a dig site that has much potential.

The presence of remains of species like the wooly rhinoceros indicatest that the accumulation of bones started in a period of intense cold during the last glaciation.

The excavations at the cave of La Rexidora, apart from the aforementioned cranium, have yielded, to date, a set of more than 150 bones of this extinct species of bison, most of them found in an excellent state of conservation, belonging to several different individuals. Other species found in this dig site include the deer, the hyena and the wooly rhinoceros. The presence of this last species indicates that the accumulation of bones started in a period of intense cold during the latest glaciation.

The bison cranium of La Rexidora is the most complete one of this species that has been recovered so far in Asturias and it is among the best preserved ones of the Iberian Peninsula. The piece has conserved most of the neurocranium (including the frontal, the occipital, the base of the cranium, the brain cavity and the bases of the bone nuclei of the horns), a sizable portion of the right lateral of the splacnocranium (including the eye sockets and the right maxillae), the nasal cavitt and a great portion of the nucleus of the right horn. The sample is, therefore, in a very good state of conservation, which makes it quite rare, given that craniums, in general, and those of the great hervibores, in particular, are very fragile anatomical elements.

Protagonist of the paintings at Altamira or Covaciella

The steppe bison has been one of the most artistically represented species by humankind during the Paleolithic Period, both in cave paintings and mobile art. Numerous Paleolithical representations of bisons have been found throughout Europe, most notably those of Altamira (Santillana del Mar) and Covaciella (Cabrales), due to their beauty and degree of detail. Thanks to the precision of those artists we now know that, for example, the steppe bison had a high, dark crin, a characteristic that is impossible to know in any other way, since these features are not fossilized.

The steppe bison (Bison priscus) is an extinct species that disappeared from Europe and Asia around 10,000 years ago. Its aspect would be close to that of the current European bison (Bison bonasus), though its size was considerably larger (up to 2.7 meters of length and almost 2 meters of height at the shoulder). Their horns were much larger than those of any modern species of bison, reaching 1.2 meters of length from side to side. Despite being a species close to the modern European bison, an animal that lives mainly in the woods, steppe bisons would live in a way more similar to that of the American bison, since they fed mostly on herbs.

A laborious restoration

Despite the good state of conservation of the bones, the piece was found in conditions of extreme frailty, with much humidity and very decalcified since it has been in constant contact with mud during millenia. The process of excavation and extraction was specially complex. The researchers constructed a polyurethane cover that allowed them to extract the remains in the best possible conditions.

The piece was extracted in numerous fragments that demanded a laborious restoration that spanned a month and a half. In the first place, each fragment was washed to remove any remains of clay. Afterwards, they were consolidated and, finally, the cranium itself was reconstructed, a process that proved to be difficult due to the small size of many of the pieces and the complexity of the anatomy of the cranium of the bison.

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Close-up of the cranium of bison reconstructed by the laboratories of the Faculty of Geology of the University of Oviedo.