The ecology of the Lower Cretaceous coelacanths from Las Hoyas Konservat- Lagerstätte (Cuenca, Spain): A new insight after the integration of palaeontological and sedimentological data

Abstract

Coelacanths are very rare in the upper Barremian fossil site of Las Hoyas (Cuenca, Spain). However, being one of the few predatory ichthyophagous fi shes preserved at the locality, understanding their ecology is fundamental to continue advancing in our comprehension of the dynamics of this palaeowetland. A previous study based on the size distribution of the coelacanth specimens suggests that a natural population of this species did not inhabit the excavated area of Las Hoyas, perhaps due to them practicing habitat partitioning. Here we analyze the sedimentological characteristics of the laminae where these fossils were preserved. In the light of the extensive previous knowledge on the stratigraphy, depositional environments and evolution of Las Hoyas, we conclude that coelacanth fossils are preserved in "wet" facies associations, indicating that they were not present in this part of the wetland permanently, but during periods of overall fl ooding of the system and high connectivity among the diff erent environments composing the regionalscale wetland.

A new enantiornithine specimen from the Lower Cretaceous of Las Hoyas: avifaunal diversity and life-history of a wetland Mesozoic bird

“…As mentioned above, the seasonality and cyclicity of the wetland have been linked to both changes in the fossil assemblages and is also evident in the life-history attributes of fishes, arthropods and plants inhabiting the wetland during different seasons (Buscalioni & Fregenal-Martínez, 2010;Martín-Abad & Fregenal-Martínez, 2021). Like other enantiornithine birds studied osteohistologically, it appears that this bird experienced rapid growth during early stages of ontogeny, and that during later ontogeny they experienced cyclical slow growth for protracted periods (Chinsamy et al, 1995(Chinsamy et al, , 2019Cambra-Moo et al, 2006;Zhang et al, 2013;Wang et al, 2014b;Atterholt et al, 2021).…”

“…Previous studies have shown that the internal lithologies of the laminated limestones were ordered into a gradient of microfacies attributed to seasonality of the original environment (Buscalioni & Fregenal-Martínez, 2010). Also, the life-history and palaeobiology of its biota was intricately linked to the palaeoenvironment, thus inherently influenced by the notable seasonality Martín-Abad & Fregenal-Martínez, 2021).…”

“…Considering this, close morphotypes or even intraspecific variability (e.g., dimorphism, polymorphism, and specially ontogeny given the osteohistological differences) cannot be ruled out. Given the rich fossil record of birds and the short time recorded at the Las Hoyas fossil site, it is likely that this record is capturing this type of variability, as is the case for fishes, arthropods, and plants (Buscalioni & Fregenal-Martínez, 2010;Martín-Abad & Fregenal-Martínez, 2021). Intraspecific variability has been widely studied in the Early Cretaceous Confuciu-sornis sanctus (Chiappe et al, 2008;Marugán-Lobón et al, 2011;Chinsamy et al, 2013;Marugán-Lobón & Chiappe, 2022) -these studies have documented variation in size (across a growth series), sexual dimorphism, and allometry within this Chinese bird species.…”