A comunicação intitulada "Diplodocoidea (Sauropoda) as key to understanding the environmental and ecological context of the Jurassic/Cretaceous transition", da autoria de Joana Órfão (IDL-FCUL, GBE-UNED) e co-autores, teve como objetivo demonstrar como o registo fóssil de diplodocoides pode ajudar a compreender melhor o turnover faunístico da transição Jurássico/Cretácico. Através da aplicação de um conjunto integrado de metodologias analíticas ajustadas a estudos de paleodiversidade e paleobiogeografia, demonstrou-se que apesar da diversidade dos diferentes clados de Diplodocoidea terem sido afectados de maneiras distintas pelas alterações ambientais características deste período de transição, a existência de distintas distribuições geográficas para os subclados Flagellicaudata e Rebbachisauridae não estará ligada a factores climáticos. Identificou-se também a existência de um efeito Lagerstätten nas curvas globais de diversidade de Diplodocoidea, ligado à Formação Morrison (Jurássico Superior, Estados Unidos), e que pode ser mitigado através da implementação de metodologias adequadas de estimação, tais como o shareholder quorum subsampling (SQS). Segue em baixo o resumo da comunicação, em inglês.
The Jurassic-Cretaceous boundary (J/K), approximately 145 million years ago, coincided with the gradual opening of the North Atlantic and the Tethys Sea. During this period, there was a general eustatic sea-level rise, accompanied by global cooling, a general increase in precipitation and more pronounced seasonality in certain parts of the planet. These environmental shifts had a profound impact on marine and terrestrial life, evident in a phenomenon of faunal turnover and a global sharp diversity decline that are well documented in the fossil record. Larger and more specialised terrestrial taxa such as Sauropoda, a diverse group of large herbivorous dinosaurs, were disproportionately affected by these changes. Notably, iconic Late Jurassic neosauropod clades such as Diplodocinae and Camarasauridae started to decline and/or went extinct during the J/K transition, whereas Titanosauriformes and Rebbachisauridae began to diversify and would later dominate Cretaceous landscapes. Herein, we focus on the sauropod clade Diplodocoidea and demonstrate the potential of its fossil record to advance our understanding of the J/K faunal turnover, by applying an integrated approach comprising paleobiogeographic and paleodiversity methodologies. We demonstrate that the main Diplodocoidea subclades were differently affected by the J/K environmental changes, with Late Jurassic Flagellicaudata declining markedly whereas Rebbachisauridae persisted until the Early to mid-Cretaceous. Additionally, and despite apparent differences in paleogeographic distribution, the climatic niche space occupied by both clades is seemingly identical, suggesting a possible niche takeover mechanism within Diplodocoidea. Finally, we compare our paleodiversity estimates with those from previous studies in literature, while also assessing the influence of sampling biases in our results. Notably, we recover a Lagerstätten effect for the Morrison Formation (Upper Jurassic, USA) that can be mitigated through adequate methodological techniques such as Shareholder Quorum Subsampling.
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