A young mammoth and one of the largest groups of woolly rhinoceros in the Peninsula discovered in Asturias
December 10, 2013
Researchers from the University of Oviedo have managed to recover one of the most abundant cold-environment animal groups of the Iberian Peninsula
Around 35,000 years ago, a young one-year-old mammoth, which had a life expectancy of 60 years, walked on what today is Puertas de Vidiago (Asturias), distanced itself from the rest of its group and the care of its mother, and approached a more dangerous area.
"It was a depression in the terrain, called a collapse sink-hole, that led to one of the countless caves of the sub-level of the Asturian Orient", explains Diego Álvarez Lao, professor of the Department of Geology of the University of Oviedo and coordinator of the dig site of Jou Puerta, whose results have just been published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
Just like the other 33 animals that shared the fate of the young mammoth during the 6,000 years during which the sink-hole that led to the cave remained open, once the animal fell into it, it was unable to crawl back out, if it even survived the fall in the first place.
"Many of the remains that we have recovered belong to young individuals, less experienced and knowing of the risks of the terrain, such as the two woolly rhinoceros of between six and seven years and a young leoppard, all of which still had their milk teeth", explains the paleontologist.
A herculean rhinoceros
Among the remains of woolly rhinoceros recovered, Álvarez Lao highlights "a humerus of a great size and strength that, due to its dimensions, must have belonged to one of the largest woolly rhinoceros documented in the global fossil registry".
With 105 remains belonging to three individuals (two young and an old adult), "the samples of this species found at Jou Puerta is one of the richest of the Iberian Peninsula", argues Álvarez Lao. More precisely, explains the palentologist, the team managed to extract a "very well conserved" lower jaw, "very complete" remains of a posterior limb, vertebrae, a pelvis and other remains of "almost every part of the body, apart from numerous individual teeth".
The biggest deer in natural history
The rhinoceros were not the only already-exincted colossi that shared the same fate. An example of the biggest deer that ever lived in the history of evolution was also trapped in Jou Puerta: the megaloceros, or giant deer.
"It is a rare species in Iberian dig sites, and we were able to recover fragments of an outstanding horn from Jou Puerta", says Álvarez Lao. In fact, these horns measured, from one end to the other, three and a half meters, and each horn measured, from the base to the end, around 1.8 meters. The deer itself measured more than two meters up to the cross (the "shoulder" of the animal).
Herbivores, a window to an ancestral climate
Its status as a natural trap and its posterior filling with mud and stones have allowed the dig site to preserve the bones until today in an exceptional state of conservation, sheltered from erosion and the fragmentary action of carnivores. Moreover, a trap with these features, explains Álvarez Lao, prevents the selection present in dig sites as a result of the activity of predators, both human and animal, that may limit themselves to hunting few species according to their dietary preferences.
"Since the animal fell down the whole, the dig site of Jou Puerta provides a widely representative sample of the fauna of herbivores that populated the Cantabrian area during the time this sink-hole was open, which coincides with some of the coldest episodies of the last glaciation", points out the paleontologist and professor of the University of Oviedo.
With respect to the carnivore fauna, the fact that the remains of only one individual, in comparison to the 33 herbivores found, is mainly due to the fact that the former, with their better spatial vision, are less likely to fall into this kind of accidents, explains Álvarez Lao. Nevertheless, "hervibores provide us with a great deal of information about the climate of that period, since they are specialized in a vegetable diet according to the climate, while carnivores adapt more easily", claims the paleontologist.
One territory, fauna from three environments
The presence at the dig site of Jou Puerta of hervibores that typically belonged to glacial climates, such as the mammoth or the woolly rhinoceres, uncommon in Iberian dig sites, indicates that the remains were placed during a very cold and arid time, concludes the researcher. Nevertheless, the most common species found in Jou Puerta is the deer, which, alongside roe deers, is usually found in mild climates.
This co-existence of glacial and mild-climate faunas in the same territory is, according to Diego Álvarez Lao, "a peculiarity of the Iberian dig sites, especially those of the Cantabrian region, that is not found anywhere else in Europe", claims the researcher.
Even though the dig site is currently at 28 meters over the sea level, the presence of mountain species, like the chamois or the mountain goat, not commonly found at that height, is due to the particular orography of the area, with mountains that reach more than 1,000 meters high less than five kilometers away from the cave. Nowadays, and after Jou Puerta has been completely dug, the cave that contains it has disappeared under the Autovía del Cantábrico.