La diversidad de saurópodos de la Formación Morrison en el 85th Annual Meeting de la SVP

La 85th Annual Meeting de la Society of Vertebrate Paleontology se celebró entre el 11 y el 15 de noviembre en la ciudad inglesa de Birmingham. Entre homenajes a Black Sabbath y tributos a la ciudad de Tolkien, también hubo tiempo para que miembros del Instituto Dom Luiz (Universidad de Lisboa), del Grupo de Biología Evolutiva (UNED) y del Institut Catalá de Paleontologia Miquel Crusafont (UAB) presentaran una comunicación titulada "The Morrison Fm. (Late Jurassic, USA) Sauropoda diversity: a blink into the (global) past". Esta presentación en formato póster versó sobre los niveles de diversidad de saurópodos que pueden encontrarse en esta unidad geológica, caracterizada por su notable extensión cronogeográfica. Joana Órfão y sus coautores intentaron evaluar el impacto de la inclusión de los hallazgos pertenecientes a la formación Morrison en las curvas de diversidad del grupo de saurópodos Diplodocoidea mediante modelos GLS. Los resultados obtenidos muestran que esta formación podría producir un efecto Lagerstätten (una inflación artificial de la diversidad causada por la sobrerrepresentación de algunos taxones) en los patrones de diversidad de los diplodocoideos cuando estos se estiman con métricas no corregidas. Sin embargo, este efecto no se observa en los patrones obtenidos a partir de estimaciones que mitigan los efectos del sobremuestreo, por ejemplo, mediante el método de quorum subsampling. A continuación se presenta el resumen completo de la comunicación:

The Upper Jurassic Morrison Formation in the western US has long been a rich source of paleontological discoveries. These continental sediments were deposited across 1.2 million square km of alluvial plains with rivers, floodplains, and seasonal lakes. Its wide extent and exceptional fossil preservation have made the Morrison Fm. one of the most intensively studied geological units globally. Although dinosaurs from the Morrison Fm. have been known since the late 19th century, discoveries continue to enhance our understanding of Late Jurassic biodiversity. Although the high diversity in the Morrison Fm. is generally accepted as genuine, the extent to which sampling bias and fossil record limitations may distort diversity estimates remains unclear. Sauropod dinosaurs are especially abundant in the Morrison Fm., with genera such as Camarasaurus, Diplodocus, Brachiosaurus, and Apatosaurus among its most iconic. Many sites within the formation have produced fossils from multiple coexisting sauropod taxa. The global peak in sauropod diversity during the Late Jurassic, often cited in the scientific literature, appears to be largely driven by discoveries from the Morrison Fm. However, reconstructing the true sauropod diversity in this formation is challenging. Factors such as stratigraphic variation, taphonomic processes, ontogenetic changes, evolutionary dynamics, and environmental influences may obscure accurate diversity estimates. Paradoxically, despite the formation's extensive fossil record and long depositional history, some researchers argue that its sauropod diversity is still underestimated. This raises caution about using formations like the Morrison Fm. as the basis for extrapolating global diversity patterns. In light of this, we investigated whether a Lagerstätten effect associated with the Morrison Fm. might be influencing global Late Jurassic Diplodocoidea diversity patterns. We estimated global diversity for this clade both with and without Morrison Fm. occurrence data and used a GLS-based modeling approach to evaluate the roles of abiotic factors, sampling biases, and preservational biases in shaping these paleodiversity trends (e.g. tetrapod bearing formations and collections, emerged land area, paleotemperature, sea level, stage length). Preliminary results from our best-fitting models support the hypothesis that the Morrison Fm. exerts a Lagerstätten effect, identifying it as a significant influence on global Diplodocoidea diversity curves.

Funding Sources FCT Portugal: UI/BD/151441/2021 (PhD grant) and CEECIND/00726/2017; Spanish Ministry of Science, Innovation and Universities: JDC2023-050836-I (Juan de la Cierva grant).

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Más información:

• Referencia: Órfão, J., de Celis, A., Ortega, F., Mocho, P. (2025). The Morrison Fm. (Late Jurassic, USA) Sauropoda diversity: a blink into the (global) past. In Hunter, J., Turner, N., Vlachos, E., Whatley, R. (Eds.) 85th Annual Meeting of SVP. Abstract book. Birmingham, 469-470.