The vertebrate assemblage of Buenache de la Sierra (Upper Barremian of Serrania de Cuenca, Spain) with insights into its taphonomy and palaeoecology

The Upper Barremian deposits of La Huerguina Limestone Formation in the Serrania de Cuenca (Iberian Ranges, Spain) contain rich continental fossil associations preserved under a great diversity of taphonomic conditions in alluvial and lacustrine deposits. The vertebrate association retrieved from the Buenache de la Sierra Subbasin is described in detail and compared to other localities of La Huerguina Formation (Una and Las Hoyas). The association was found at El Ingles Quarry, in a level composed of grey to ochre slabby marly siltstones, sometimes slightly sandy, with abundant plant macroremains sedimented in a small stagnant pond. The pond was part of a complex and mixed (siliciclastic and carbonatic) depositional system, controlled by a seasonal subtropical climate. It consisted of distal alluvial plains grooved by narrow channels with scattered ponds, small shallow lakes and palustrine marshy areas, fed by superficial water and groundwater. These underwent seasonal floods followed by slow draining and evaporation and finally a seasonal period of desiccation. Three different points from the same level were sampled in the quarry. Microfossils were extracted with a sieving table and pressurized water, yielding more than 2000 fossil specimens. The assemblage is composed of anatomically identifiable elements of charophytes, ostracods, molluscs, fish, albanerpetontids, anurans, lepidosauromorphs, chelonians, a pterosaur?, theropods, crocodyliformes, eggshells and a mammaliaforms?, as well as bone splinters, shell fragments and plant remains. Charophyte utriculi, ostracods, isolated teeth and eggshells are the most abundant elements. The association has yielded Allocaudata remains as well as an unidentified family of Anura (based on a maxilla fragment) and an unidentified family of Neosuchia (based on isolated teeth). The Buenache assemblage shows a sound demy (i.e. fossils found in their original habitat) of an aquatic freshwater ecosystem, as is natural for a wetland ecosystem. The wide variety of microhabitats linked to water availability in wetlands gives rise to a complex faunal assemblage in which four categories of species can be recognized as in extant wetlands: obligate, amphibious, facultative and incidental. Despite the taphonomic differences between Buenache, Una and Las Hoyas, a common palaeoecological structure is documented. (C) 2008 Elsevier Ltd. All rights reserved.