Scientists have uncovered evidence of a warm tropical sea that covered parts of Egypt’s Western Desert more than 70 million years ago, after finding 14 fossilized teeth of five shark species in the Abu Tartur Plateau.
The discovery indicates that the area, which is now part of one of the driest environments in the world, was once home to a rich marine ecosystem, inhabited by a diverse number of sharks, small fish, invertebrates and marine reptiles.
Scientists discovered the teeth in phosphate deposits on the Abu Tartur plateau, located between the Kharga and Dakhla oases in the Western Desert. The area is one of Egypt's most important phosphate sites, but it also holds a geological record that reveals the nature of the environment that existed there tens of millions of years ago.
By comparing the discovered teeth with known fossils from other regions, scientists, led by a team from Cairo University, identified five extinct species of sharks:
Cretalamna cf. maroccana, and Scapanorhynchus cf. raphiodon, and Serratolamna cf. serrata, Squalicorax bassanii, and Squalicorax pristodontus.
These species have never been recorded in the Abu Tartur Plateau before, and two of them, Serratolamna cf. serrata and Squalicorax bassanii, have never been documented in Egypt before. The discovery brings the number of known shark species from the region to at least seven.
One specimen was particularly noteworthy, as the tooth attributed to Scapanorhynchus cf. raphiodon may represent the first specimen of this species found in Africa. Researchers believe it may also be the youngest known specimen of this species in the fossil record.
The shapes of the teeth reveal a clear difference in the way sharks fed. Some teeth were long and thin, while others were wide and serrated, and some had a curved shape.
Scientists believe this diversity reflects the variety of prey the sharks fed on, and that different species occupied multiple locations within the ecosystem. The presence of teeth from both nearshore and deeper-water species also indicates the diversity of marine environments in the area.
Sharks were not alone in that sea, as fossil evidence shows the presence of small fish, invertebrates, and predatory marine reptiles, indicating a complete food web that extended from microorganisms to larger predators.
Scientists believe that ocean currents helped enrich this environment with nutrients by transporting cold, nutrient-rich water from the depths to the surface, a process known as hydrothermal erosion. This, in turn, fostered the growth of plankton and microorganisms, which formed the basis of the marine food chain.
These creatures lived during the Cretaceous period, which lasted from about 145 to 66 million years ago, a time when the Earth's climate was warmer and wetter than it is today.
Large parts of the area that now forms Egypt were covered by the warm waters of the Tethys Sea, while the Abu Tartur plateau was probably located near the outer continental shelf and the top of the slope leading to deep water.
Over millions of years, as geological conditions changed and seawater receded, the marine environment that once covered the area disappeared, leaving behind deposits and fossils that preserved a part of its history.
The newly discovered shark teeth provide new evidence of the nature of this ancient environment and help to reconstruct a marine ecosystem that flourished in what is now part of Egypt's Western Desert.
The results of the study were published in the journal "Cretaceous Research".
