A LAKE FULL OF LIFE

After washing some 20 tonnes of sediment, nearly 20,000 biological remains were collected, of which some 8700 have so far been identified. The micropaleontological sample, which was studied by Pablo Peláez-Campomanes de Labra, includes the remains of four main groups of animals: mammals, reptiles, amphibians and birds. Mammals make up some 97% of the identified material.

From a taphonomic point of view, the fossil-bearing layers of Casa Montero have preserved their contents exceptionally well. Indeed, the association of microvertebrates is unique for the continental Middle Miocene.
Fossilised remains are found throughout the fossil-bearing layer. Some areas include the remains of individual animals, sometimes in their correct taxonomic layout, while others contain the remains of several individuals. The proportion of cranial remains (upper and lower jawbones and isolated jugal teeth) are particularly numerous and better preserved than the postcranial skeletal remains. Such accumulations reflect a notable degree of transport before eventual burial.

The great majority of the remains collected show notable deformation consistent with compression, although many bones have not been broken. This deformation might be explained by a demineralisation of the bones and their compression after burial. This compression, however, caused abundant fractures in the enamel of the tooth remains, a consequence of its rigidity.

Some of the skeletal remains bear marks made by rodents and/or lagomorphs. These must have been made before the bones were buried.