The ancient Saharan Seaway shows how the climate and creatures of the Earth can undergo extreme changes

A new article to appear in the Bulletin of the American Museum of Natural History integrates 20 years of research conducted by a diverse scientific team and describes the ancient trans-Saharan Seaway of Africa that existed 50 to 100 million years ago in the region of the current Sahara desert. Under the direction of Maureen O. Leary, professor of anatomical sciences at the Renaissance School of Medicine at Stony Brook University, this article is a comprehensive synthesis. It contains the first reconstructions of extinct aquatic species in their habitats along the Seaway and puts into context the climate changes in sea level that may occur on Earth.

The area where the Sahara Desert is located was once submerged, which contrasts starkly with the current arid climate. This dramatic climate difference over time is recorded in the Rock and Fossil Archives of West Africa during a period ranging from the Cretaceous-Paleogene (KPg) boundary. West Africa was divided in two by a shallow body of salt water that spilled over the continental crust at a time when sea levels were high. The document includes an evaluation and ongoing analysis of three expeditions led by Professor O. Leary (1999, 2003 and 2008) in the context of rock exposures in the Sahara Desert in Mali, followed by laboratory work on fossil discoveries in the region.

"The fossils discovered during the expeditions indicate that the sea was home to some of the largest sea snakes and catfish ever seen, extinguished and giant fish compared to their modern-day parents, mollusc-shellfish, tropical invertebrates , long-snouted crocodilians, young mammals and mangrove forests, "said Professor O. Leary, also an associate researcher in the Division of Paleontology at the American Museum of Natural History. "Since the size of the seaway and its geography have often changed, we propose that" water islands "result that have stimulated the gigantism of the species."

The document contains the first reconstructions of ancient elephant parents and large predators at the apex such as sharks, crocodilians and sea snakes.

"Through our analysis and new technologies, such as a computer-aided seaway map, our work is an important step in improving our understanding of the KPG's border, the period of time." Extinction of non-avian dinosaurs, "said Professor O. Leary. .

She and her colleagues point out that the paper puts into context the climate and sea level changes that may occur on Earth.

For example, scientists are currently predicting that global warming will cause the sea to rise two meters by the end of the 21st century. The study published in the Bulletin describes how, in the Upper Cretaceous period, sea-level rise far exceeded that predicted by human-induced climate change. In the Upper Cretaceous, the sea level was 300 m higher than today – 40% of the current land was submerged, which is very different from today. This information highlights the dynamic nature of the Earth.

Professor O & # 39; Leary explained that scientists did not have detailed terrestrial / coastal stratigraphic sections containing fossils on all continents, in order to accurately examine how the KPG boundary is occurring. was unfolding on a global scale. There is only one good coastal or terrestrial section containing vertebrate fossils in the western United States. Expeditions to Mali, she added, have created a new imperfect section. Some of the oldest paleogens are lacking, while contributing to a better understanding of world events 50 to 100 million years ago.

Professor O & # 39; Leary and many colleagues from around the world participated in these expeditions to search the fossils and conduct the research. The collaborative research team is composed of paleontologists and geologists from the United States, Australia and Mali.

"Few paleontologists had worked in the area, given its isolation and freezing temperatures at 125 ° F. The changing sand dunes made it difficult to search for rocky outcrops and, even worse, a rainstorm. lightning flooded the roads making navigation almost impossible, "said Leif Tapanila. , PhD, professor of geoscience at Idaho State University and co-author of the article. "These expeditions would not have succeeded without the experience of local Malian drivers and guides, and I was amazed by the quality and diversity of marine fossils we found in the Sahara Desert. . "

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The research was funded by the National Science Foundation (SGER Award: 0827993), the National Geographic Society, the LSB Leakey Foundation, the American Museum of Natural History, and Idaho State University.

Paper: http: // digitallibrary.AMNH.org /manipulate/2246 /6950