Seasonality and Paleoecology of the Late Cretaceous Multi-Taxa Vertebrate Assemblage of “Lo Hueco” (Central Eastern Spain)

Isotopic studies of multi-taxa terrestrial vertebrate assemblages allow determination of paleoclimatic and paleoecological aspects on account of the different information supplied by each taxon. The late Campanian-early Maastrichtian “Lo Hueco” Fossil-Lagerstätte (central eastern Spain), located at a subtropical paleolatitude of ~31°N, constitutes an ideal setting to carry out this task due to its abundant and diverse vertebrate assemblage. Local δ(18)O(PO4) values estimated from δ(18)O(PO4) values of theropods, sauropods, crocodyliforms, and turtles are close to δ(18)O(H2O) values observed at modern subtropical latitudes. Theropod δ(18)O(H2O) values are lower than those shown by crocodyliforms and turtles, indicating that terrestrial endothermic taxa record δ(18)O(H2O) values throughout the year, whereas semiaquatic ectothermic taxa δ(18)O(H2O) values represent local meteoric waters over a shorter time period when conditions are favorable for bioapatite synthesis (warm season). Temperatures calculated by combining theropod, crocodyliform, and turtle δ(18)O(H2O) values and gar δ(18)O(PO4) have enabled us to estimate seasonal variability as the difference between mean annual temperature (MAT, yielded by theropods) and temperature of the warmest months (TWMs, provided by crocodyliforms and turtles). ΔTWMs-MAT value does not point to a significantly different seasonal thermal variability when compared to modern coastal subtropical meteorological stations and Late Cretaceous rudists from eastern Tethys. Bioapatite and bulk organic matter δ(13)C values point to a C(3) environment in the “Lo Hueco” area. The estimated fractionation between sauropod enamel and diet is ~15‰. While waiting for paleoecological information yielded by the ongoing morphological study of the “Lo Hueco” crocodyliforms, δ(13)C and δ(18)O(CO3) results point to incorporation of food items with brackish influence, but preferential ingestion of freshwater. “Lo Hueco” turtles showed the lowest δ(13)C and δ(18)O(CO3) values of the vertebrate assemblage, likely indicating a diet based on a mixture of aquatic and terrestrial C(3) vegetation and/or invertebrates and ingestion of freshwater.