2023-08-10 18:00:29
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An international team of scientists, led by Egyptian researchers, has made the pioneering discovery of a new species of extinct whale, ‘Tutcetus rayanensis’, which inhabited the ancient sea that covered present-day Egypt some 41 million years ago, as published in the journal ‘Communications Biology’.
This new whale is the smallest basilosaurid known to date and one of the oldest records of that family in Africa. Despite its diminutive size, Tutcetus has provided unprecedented data on the life history, phylogeny, and paleobiogeography of the earliest whales.
The Basilosauridae, a group of extinct fully aquatic whales, represent a crucial stage in the evolution of whales, in their transition from land to sea. They developed fish-like characteristics, such as a streamlined body, a strong tail, fins, and a caudal fin, and had the last hind limbs visible enough to be recognized as “legs,” which were not used for walking, but rather for walking. possibly to mate.
The newly discovered ‘Tutcetus rayanensis’ was found in middle Eocene rocks and, unambiguously, helps clarify the picture of the early evolution of whales in Africa. The name of the new whale is inspired by both Egyptian history and the place where the specimen was found.
The name of the genus, Tutcetus, combines “Tut” –in reference to the famous Egyptian pharaoh Tutankhamen– and “cetus”, Greek for whale, to highlight the small size of the specimen and its condition as a subadult. The name also commemorates the discovery of the king’s tomb a century ago and coincides with the imminent opening of the Grand Egyptian Museum in Giza. The species name, rayanensis, refers to the protected area of Wadi El-Rayan, in Fayoum, where the holotype was found.
Hisham SalamProfessor of Vertebrate Paleontology at the American University in Cairo, founder of the Center for Vertebrate Paleontology at Mansoura University and director of the project, points out that “the evolution of whales from land animals to beautiful sea creatures embodies the wonderful adventurous journey of life”.
“Tutcetus is an extraordinary discovery that documents one of the early phases of the transition to a fully aquatic lifestyle that took place on that trip,” he adds.
The holotype specimen consists of a skull, jaws, hyoid bone, and atlas vertebra of a small subadult basilosaarid whale that is embedded in a block of heavily compacted limestone. With an estimated length of 2.5 meters and a body mass of approximately 187 kilograms, Tutcetus is the smallest basilosaurid known to date.
Lead author, Mohammed Antarfrom the Center for Vertebrate Paleontology at the University of Mansoura, and the National Focal Point for Natural Heritage explains that “Tutcetus significantly broadens the size range of basilosaurid whales. and reveals considerable disparity among whales during the middle Eocene.”
“Investigation of the oldest layers of the Fayum strata may reveal the existence of an older set of primitive whale fossils, which could influence our current knowledge of the appearance and dispersal of whales,” he adds.
Sample of the right area of the jaw of Tutcetus rayanensisMUVPNature
Sanaa El-Sayed, a doctoral student at the University of Michigan (United States) and a member of the Sallam Laboratory, and a co-author of the study, points out that “the relatively small size of Tutcetus (188 kg) is primitive retention or could be related to the global warming event known as the “Late Lutecian Thermal Maximum (LLTM)”.
Thanks to detailed analysis of Tutcetus teeth and bones using computed tomography, the team has been able to reconstruct the pattern of growth and development of this speciesproviding unprecedented insight into the life history of the first whales.
The rapid dental development and small size of Tutcetus suggest a precocial lifestyle with a rapid pace of life for early whales. In addition, the discovery of Tutcetus contributes to the understanding of the early success of basilosaurs in the aquatic environmenttheir ability to outperform amphibian mother whales and their ability to opportunistically adapt to new niches after their relationship with amphibians breaks.
Abdullah Gohar, a PhD student at Mansoura University, a member of the Sallam lab and co-author of the study, says that “Modern whales migrate to warmer, shallower waters to breed and breed, reflecting conditions found in Egypt 41 million years ago”.
“This supports the idea that what is now known as the Fayum was a crucial breeding ground for ancient whales, possibly attracting them from various locations and, in turn, attracting larger predatory whales such as Basilosaurus.” .
The team’s findings have important paleobiogeographic implications, as they demonstrate that basilosaurs probably achieved rapid expansion into the southern hemispherereaching high latitudes in the middle of the Eocene.
Erik Seiffert, Professor and Professor of Integrative Anatomical Sciences at the University of Southern California and co-author of the study, said: “The Eocene fossil beds of the western desert of Egypt have long been the most important in the world for understanding the early evolution of cetaceans and their transition to a fully aquatic existence”. Seiffert added: “The discovery of Tutcetus demonstrates that this region still has much to tell us about the fascinating history of the evolution of whales“.
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