A holistic approach to the palaeoecology of Las Hoyas Konservat-Lagerstätte (La Huérguina Formation, Lower Cretaceous, Iberian Ranges, Spain)

Abstract

The Las Hoyas fossil site (Lower Cretaceous, Iberian Ranges, Spain) is a classic lacustrine Fossil-Lagerstätte that exemplifies the features predicted by the original concept of Konservat-Lagerstätten in relation to the quantity of remains, quality of preservation, completeness, and preservation by a combination of obrution, stagnation and, in this case, mainly bacterial sealing. Fossils are preserved in rhythmically laminated limestones deposited in a environment that underwent strong, climatically driven cyclical oscillations in water level within the framework of a seasonal, subtropical, regional-scale wetland. Extensive systematic layer-bylayer excavation and geological research have resulted in a comprehensive understanding of the stratigraphy and sedimentology of the locality and its regional palaeogeography. Two approaches have allowed the palaeoecology of the fossil association to be reconstructed. Firstly, autoecological reconstructions of the fossil groups are supplemented by palaeoenvironmental reconstructions based on the sedimentology. This considers taphonomic features and the ecological structure of the whole association, including vegetation and animals. The organization of the ecosystem resembles that of extant lentic ecosystems. It is dominated by obligate aquatic and amphibious organisms; facultative terrestrial organisms are scarce. Several lines of evidence from flora and fauna indicate strong seasonality and water stress. The second approach is dynamic and aims to unravel the information transferred to the fossil record about ecological dynamics and evolution by combining stratigraphical and palaeontological information and integrating this in a spatial and temporal framework. This analysis illustrates that Las Hoyas has a significant facies bias, reflecting alternating

A new trackway possibly made by a trotting theropod at the Las Hoyas fossil site (Early Cretaceous, Cuenca Province, Spain): Identification, bio-dynamics and palaeoenvironmental implications

“…This ichnofacies is named Mermia and contains signs of characteristic benthic invertebrate activity -mainly that of crustaceans, worms, and insect larvae within continental environments (Buatois and Mángano, 2011). This Mermia interpretation is congruent with the body fossils present, which mainly represent obligate aquatic organisms such as benthic invertebrates and fish (Gibert et al, 1999;Buatois et al, 2000;Buscalioni and Fregenal-Martínez, 2010;Gibert et al, 2016). The Las Hoyas Mermia ichnoassemblage is rather peculiar, however, given the presence of archosaur trackways (Gibert et al, 2016).…”

“…The archosaur ichnofossils at Las Hoyas are less abundant than those of invertebrates, but have yielded significant information on the palaeoecology and palaeoenvironmental conditions of the ecosystem (Buscalioni and Fregenal-Martínez, 2010;. The tetrapod ichnofossils include some shallow footprints forming a crocodile trackway , a discovery that obliged the established palaeoenvironmental interpretation of a deep lake to be revisited and replaced with that of a rather shallow aquatic environment .…”

“…The tetrapod ichnofossils include some shallow footprints forming a crocodile trackway , a discovery that obliged the established palaeoenvironmental interpretation of a deep lake to be revisited and replaced with that of a rather shallow aquatic environment . Buscalioni and Fregenal-Martínez (2010) reported Las Hoyas to have few tetrapod traces, although crocodilian body fossils are abundant. Dinosaurs are represented only by three specimens and species: Pelecanimimus polyodon (Pérez-Moreno et al, 1994), Concavenator corcovatus (Ortega et al, 2010), and cf.…”

“…Mantellisaurus (Llandres et al, 2013). In fact, dinosaurs appear to have been only incidental organisms in the Las Hoyas ponding area (Buscalioni et al, 2008;Buscalioni and Fregenal-Martínez, 2010).…”

Involvement of Microbial Mats in Delayed Decay: An Experimental Essay on Fish Preservation

“…In fact, microbial mats play a crucial role in the formation of microbially induced sedimentary structures (MISS) encompassing the regular deposition of sand, the accumulation of sediment, and the subsequent mat cover (Noffke, 2009). The frequent association of fossilized microbial mats with better-preserved fossils has been treated as a positive consequence for exceptional preservation, accumulation and ecological fidelity in Konservat Lagerstätten (Gall et al, 1985;Gall, 1990;Seilacher et al, 1985;Seilacher, 1990Seilacher, , 2009Behrensmeyer, 2000;Briggs, 2003b;Buscalioni and Fregenal-Martínez, 2010). Mat properties that have been proposed to promote exceptional fossil preservation include: (1) envelopment (growth of the mat over the body); (2) pseudomorphism (replication of the body surface by microbial growth); (3) protection (from scavengers and from water currents) avoiding the breakup of the corpse; (4) delay in decay rate; and (5) bioprecipitation (Briggs, 2003a).…”