Exceptional coprolite association from the Early Cretaceous continental Lagerstätte of Las Hoyas, Cuenca, Spain.

Sandra Barrios-De Pedro,José Joaquín Moratalla,Francisco José Poyato-Ariza,Ángela D Buscalioni,William Oki Wong

doi:10.1371/journal.pone.0196982

Sandra Barrios-De Pedro, José Joaquín Moratalla + Show 3 more

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https://doi.org/10.1371/journal.pone.0196982

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Abstract

Coprolites are some of the most abundant fossils at the Las Hoyas site, a well-known Early Cretaceous Konservat-Lagerstätte located in Cuenca, central Spain. The coprolite association is described, introducing taphonomic features and sedimentological properties. This study is based on a subsample of 433 fossils selected from some 2000 specimens collected. The taphonomic features of the coprolites show that their integrity, absence of desiccation marks, and volume are congruent with faeces produced and deposited in an aquatic ecosystem, which were immediately covered by microbial mats. The highest abundance of coprolites, 96%, occurs in layers linked to the presence of microbial mats. Consequently, it is likely that coprolites are taphonomically autochthonous. A dichotomous key has been made in order to delimit the morphotypes. The key is based on (1) presence/absence of spiral marks, (2) morphology of coprolite ends, including polarity, expansion, and surface, and (3) overall shape, outline, diameter, and constrictions. Twelve different morphotypes are distinguished: spiral, circular, irregular, elongated, rosary, ellipsoidal, cylinder, bump-headed lace, fir-tree, cone, straight lace, and thin lace. The association is dominated by thin-lace and cylinder morphotypes. The sizes, inclusions, and EDX analyses indicate that the Las Hoyas coprolites correspond mostly to carnivorous producers with ichthyophagous diets, as crocodiles, urodelans and different kind of fishes.

Highlights

Coprolites are fossilized faeces belonging to a group of ichnofossils called bromalites [1]; the term ‘coprolite’ was defined by Buckland in 1829 [2]
We describe the exceptional assemblage of Early Cretaceous (Barremian) coprolites from Las Hoyas Konservat-Lagerstatte in order to understand the variety and disparity of the coprolite association
In order to refine this concept, we have applied the general definitions of assemblage and association to the coprolites [66]; i.e. an assemblage is any ensemble of fossils that is recovered from the same layer, and an association is the combination of the fossils themselves plus their taphonomic properties and lithology

Summary

Introduction

Coprolites are fossilized faeces belonging to a group of ichnofossils called bromalites [1]; the term ‘coprolite’ was defined by Buckland in 1829 [2]. In order to present this complexity in a comprehensive and organized manner, we combined these characters and constructed a dichotomous key that provides a path for the categorization and diagnosis of the different morphotypes This key will help to account for the range of coprolite diversity at Las Hoyas, and can provide the basis to categorize any additional specimens or new morphotypes (Fig 5). In coprolites with very abundant remains it is virtually impossible to observe the coprolite matrix due to the concentration of inclusions Kind of inclusions: Thread-like structures (probably scales embedded in coprolite matrix), rings (probably tiny fish vertebrae embedded in coprolite matrix) and thin bony remains (some of them seem to be segmented fin rays) The abundance, both numerical and relative, of each particular morphotype is presented in Fig 9 (N = 433). Three coprolite specimens from Las Hoyas measure 5 mm long or less, and they belong to three different morphotypes each: circular, ellipsoidal, and cone

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