Seeking for the best conditions for fish fossil preservation in Las Hoyas Konservat-Lagerstätte using microbial mats

Actuotaphonomic experiments demonstrate how microbial mats prevent or delay destructive processes. The rate at which carcasses are covered is a key to their preservation. Because of the growth rate of microbial mats depends on environmental conditions, a set of experiments have been carried out emulating the Barremian environmental conditions, analysed for temperatures at 14°C and 26°C (cooler and warmer seasons respectively) and atmospheric pCO2 (1000 ppm). For this purpose, the microbial mats were grown in mesocosms within an environmental chamber. Variations in primary production were quantified by measuring changes in dissolved O2 concentration in the water. Zebrafish carcasses were laid on the mats, and their coverage rates were calculated from the daily surface area covered by the mat. The results showed that the fish was covered twice as fast at 26°C, in coincidence with the highest values for the gross primary production and community respiration of the microbial mats. Therefore, for these Barremian conditions, the early stages of carcasses preservation would take place most effectively during the warmer seasons as decomposing activity would release nutrients that would enhance, together with temperature, the growth of matsThis study was funded by the Spanish Ministry of Science, Innovation and Universities [project PID2019-105546GB-I00

A theropod trackway providing evidence of a pathological foot from the exceptional locality of Las Hoyas (upper Barremian, Serrania de Cuenca, Spain)

We describe a trackway (LH-Mg-10-16) occurring in laminated carbonated limestones of the Las Hoyas locality, Serranı´a de Cuenca, Spain. It is unmistakably a large theropod dinosaur trackway encompassing two unusual aspects, namely, wide-steps, and a set of equally deformed left footprints (with a dislocated digit). The layer also preserves other vertebrate trails (fish Undichna) and different impressions in the sediment. To address these complex settings, we devised a multidisciplinary approach, including the ichnological and taphonomical descriptions, characterisation of the rock lithofacies using thin-sections, 3D structuredlight digitalisation with a high precision of 200–400 μm, and a geometric morphometric comparison with a large sample of bipedal dinosaur trackways. Sedimentary analyses showed that the trackway was produced in a humid, benthonic microbial mat, the consistency and plasticity of which enabled the preservation of the details of the movement of the animal. The results of the geometric analysis indicate that the “wide-steps” of the trackway is not unusual compared to other trackways, providing evidence that it was made by a single individual with an estimated hip height approximately 2 m. Analogous pathologies in extant archosaurs that yield the combination of wide steps and deformed digits in the same trackway were considered. All results mutually support the hypothesis that a large theropod dinosaur, with a pathological foot, generated the trackway as it crossed an area of shallow water while slowly walking towards the main water source, thus stepping steadily over the benthonic mat over which multiple fish were swimmin

Cocodrilos fósiles del registro español. Análisis sistemático y filoginético de la familia atoposaudidae (reptilia, cocodylia)

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias. Fecha de lectura: 22-12-198

Three steps in the Cretaceous evolution of Crocodylomorpha: example from Barremian to Maastrichtian diversity in the Iberian Peninsula, and what about mid-Cretaceous gap?

Buscalioni Ángela Delgado, Vullo Romain. Three steps in the Cretaceous evolution of Crocodylomorpha: example from Barremian to Maastrichtian diversity in the Iberian Peninsula, and what about mid-Cretaceous gap?. In: Documents des Laboratoires de Géologie, Lyon, n°164, 2008. Mid-Mesozoic life and environments. Cognac (France), June 24th-28th 2008. pp. 29-32

Isolated theropod teeth from Las Hoyas (Barremian, Cuenca, Spain)

Two isolated theropod teeth from Las Hoyas are described. Current evidence suggests their identification as a carcharodontosaurid akin to Concavenator and a putative spinosaurid based on data from morphology and morphometry. These findings might represent the second carcharodontosaurid and the first Spinosauridae from La Huérguina FmSe describen dos dientes de terópodo aislados del yacimiento de Las Hoyas. Las evidencias actuales sugieren su identificación como un carcarodontosáurido similar a Concavenator y un posible espinosáurido según datos morfológicos y morfométricos. Estos hallazgos podrían representar el segundo ejemplar de Carcharodontosauridae y el primer Spinosauridae de la Formación La Huérguina

Upper Barremian microremains from Buenache De La Sierra (La Huerguina Formation, Cuenca, Spain)

González Fernando, Vullo Romain, Buscalioni Ángela Delgado. Upper Barremian microremains from Buenache De La Sierra (La Huerguina Formation, Cuenca, Spain). In: Documents des Laboratoires de Géologie, Lyon, n°164, 2008. Mid-Mesozoic life and environments. Cognac (France), June 24th-28th 2008. pp. 42-45

Estimating the Ontogenetic Status of an Enantiornithine Bird from the Lower Barremian of El Montsec, Central Pyrenees, Spain.

An Enantiornithes specimen from El Montsec was initially described as an immature individual based upon qualitative traits such as its relatively large orbit and overall proportions of the skull and the postcranium. In this study we re-evaluate the precise determination of the ontogenetic stage of this individual, establishing a cross-talk among taphonomic, anatomic, and morphometric data. The exceptional preservation of the specimen has allowed pondering ontogenetic influence versus preservational bias in features like the external patterns of bone surfaces, instead of being aprioristically considered due to taphonomic alterations only. The rough texture of the periosteal bone associated with pores in the distal, proximal and mid-shaft areas of the humeral shaft, indicates a subadult stage when compared with long bones of modern birds. Forelimb proportions of embryo and juvenile Enanthiornithes are equivalent to those of adult individuals of other taxa within this clade, though this is not a reliable criterion for establishing a precise ontogenetic stage. The El Montsec specimen may be attributed a close adulthood, yet only if growth regimes in Enantiornithes are considered equivalent to those in Neornithes birds

Vertebrate microremains from the Lower Barremian at N of Cabo Espichel (Sesimbra, Portugal): historical review and preliminary results

Rodrigues Nuno P.C., Buscalioni Ángela Delgado, Santos Vanda F., Fregenal-Martínez María A. Vertebrate microremains from the Lower Barremian at N of Cabo Espichel (Sesimbra, Portugal): historical review and preliminary results. In: Documents des Laboratoires de Géologie, Lyon, n°164, 2008. Mid-Mesozoic life and environments. Cognac (France), June 24th-28th 2008. pp. 79-82