New research challenges hypotheses about climate-driven ecosystem changes during dinosaur formation in Argentina – what’s the point?

Peer reviewed publication

UNIVERSITY OF UTAH

A group of researchers from CONICET and the University of Utah showed that during the time of the first dinosaurs, differences in the diversity and abundance of plant and vertebrate species cannot be linked to the climatic changes recorded during their deposition, in the Contrary to earlier hypotheses.

In the new study, published in the open-access journal Frontiers in Earth ScienceThe team of scientists examined several independent lines of evidence (sedimentology, clay mineralogy and geochemistry) to elucidate changes in paleoclimatic conditions (such as mean annual precipitation and mean annual temperature) within the Ischigualasto Formation. These fossil-rich sedimentary rocks were deposited by rivers and streams about 231–226 million years ago during the Late Triassic in what is now northwestern Argentina (La Rioja and San Juan provinces). At the center of the formation, the researchers observed a marked change in conditions, perhaps from warmer, drier to more temperate, wetter conditions, but no concurrent major changes were found in the fossil record.

“We conclude that variations in the abundance and diversity of species, as recorded by their first and last appearances in the fossil record, are better explained by conservation and sampling biases than by climate change,” said Adriana Mancuso, lead author and CONICET independent researcher at the Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales in Mendoza, Argentina.

“What we see is that the number of samples collected at each interval of the sequence and the chemical and physical properties that allow for greater or lesser conservation of animal and plant remains were important factors. These two factors, gathering and conservation, have a greater impact on increases or decreases in abundance and diversity than recorded climate changes,” Mancuso explained.

Although ecosystem evolution generally shows no biotic response associated with climate change, the research group observed a relationship between climatic variability and two groups of reptiles, rhynchosaurs (herbivorous early archosaurs) and pseudosuchians (archosaurs of the crocodilian lineage). . “We found that the abundance of rhynchosaurs and the extinction of some Pseudosuchia species appear to coincide with climate change,” said Randall Irmis, co-author from the U and the Natural History Museum of Utah.

Beyond drawing conclusions about these specific fossil and paleoclimate records from Argentina, the new research emphasizes the importance of an explicit framework for testing hypotheses about the relationship between climatic changes and the fossil record. “In addition to contributing to the relationship between biotic and climatic events in the Ischigualasto Formation, the work provides a methodological framework for testing climate-biota associations, highlights the data gaps that need to be filled, and makes new testable predictions that will be tested.” may in future studies,” concludes Mancuso.

Other authors are Tomás Pedernera and Cecilia Benavente from the Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (CONICET), Leandro Gaetano from the Instituto de Estudios Andinos (CONICET) and Departamento de Ciencias Geológicas from the Universidad de Buenos Aires and Benjamin Breeden from the University of Utah .

DIARY

Frontiers in Earth Science

DOI

10.3389/feart.2022.883788

METHOD OF RESEARCH

observational study

RESEARCH SUBJECT

Not applicable

ARTICLE HEADING

Paleoecological and biotic changes in the Late Triassic of Argentina: testing hypotheses of abiotic forcing at the basin level.

ARTICLE PUBLICATION DATE

June 13, 2022

By EurekAlert!

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