Tech UPTechnologyThe Madrid savannah of the Miocene

The Madrid savannah of the Miocene

What kind of ecosystem was there in Madrid about 9 million years ago?

More than 30 years ago, one of the most unique sets of paleontological sites in the fossil record was discovered to the south of Madrid. This is the Cerro de los Batallones site , where in 1991 the maxilla of an amphicyonid was found due to mineral extraction work carried out in the area. But how did the rest of this “bear-dog” come to resist the physical effects of 9 million years of fossilization? In order to answer this question we must understand the formation of this deposit.

Some 9 million years ago there were some natural traps or cavities in that region south of Madrid in which the carnivores of that time were trapped, like this amphicyon. These cavities gradually filled with sediments (very small and fine rock fragments) and just before they were silted up, small lakes formed on them. Herbivores, such as giraffes or rhinoceroses, were attracted to these places that they used to drink and were trapped on their muddy banks. In this way, two types of deposits were formed in what we now call the Cerro de los Batallones, some with the majority of carnivore remains and others with the majority of herbivore remains. This set represents one of the most diverse faunal associations in paleontology.

The first finds within this hill were limited to large carnivores such as macairodontine felids, also known as “saber-toothed” and amphicyonids or “bear-dogs”. These relatives of our current cats caused the bleeding of large prey thanks to their large upper canines. Within this group of felids, the species of Machairodus aphanistus and Promegantereon ogygia appear in the Cerro de los Batallones . The first species is the largest of this group of cats and would hunt antelope-sized prey; the second species would have the size of a current leopard and would be specialized in hunting small antelopes and rodents. Another of the most important groups of carnivores from Cerro de los Batallones would be the amphicyonids represented by the species Magericyon anceps. Although they are commonly called “dog-bears” they have nothing to do with either of these two groups since they constitute a group with its own entity. The fossil record of this species is one of the best samples in the world, since individuals of all ages have appeared, including very young ones totally dependent on their mothers .

Over the years and the different excavation campaigns, other carnivores were found. This was the case of Simocyon batalleri , the largest known ailurid or red panda, which could weigh up to 65 kg. Like its current representatives, this species had a “false thumb”. It is a small bone in the hand that was used to pinch the branches while they fed on their leaves since their real thumb does not have the ability to bend.

Hyenas are also represented on the Cerro de los Batallones, specifically one of their most primitive representatives, Protictitherium crassum . This species was the size of a jackal and like these it would feed on rodents, rabbits and birds.

Large herbivores have also been recorded in these rich paleontological sites. Among them, the mastodons belonging to the Tetralophodon longirostris species stand out . Also called proboscideans , these ancestors of today’s elephants had two pairs of incisors or guards that were straight and not curved like those found in today’s proboscideans. The reconstructions of these organisms indicate that they could reach 3 meters in height and almost 4 meters and a half in length . Other large herbivores that stand out for their richness in the Cerro de los Batallones are the rhinos . Two types appear in these deposits: the aceraterinos that did not have nasal horns and the rhinoceroses that did have nasal horns. In addition to these, the presence of Decennatherium rex stands out on the hill, a large primitive giraffe that could weigh more than 1 ton. Both the females and the males of this species had osicones or “horns” although those of the males were more developed. Finally, in the Cerro de los Batallones, the most abundant remains of herbivores are those belonging to a primitive horse called Hipparion. Unlike modern horses that only have one toe, this early organism still had 3 toes on its feet. The fossil record of these organisms is so rich that fossilized fetuses have even been found in one of the deposits.

Thanks to the exceptional fossil record that appears in the Cerro de los Batallones, it has been possible to carry out different studies on the paleoenvironment of this past habitat. Between 11 and 9 million years ago, the climate of the central peninsular changed and there was an increase in humidity . This increase caused the vegetation to increase and consequently the herbivorous fauna was enriched and with them the carnivorous fauna. In this way and due to the fossilization process, an almost complete image of the ecosystem of Madrid 9 million years ago has come down to us.

 

References:

VV.AA. 2017. The hill of the Saber Tooth Tigers: The Miocene deposits of the Cerro de los Batallones (Torrejón de Velasco, Community of Madrid). Obra Social La Caixa, Higher Council for Scientific Research (CSIC), National Museum of Natural Sciences and Regional Archaeological Museum (Community of Madrid). 8445136666 978-84-451-3666-9.

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