The newly unearthed Tutcetus rayanensis originated from middle Eocene rock and lived in the prehistoric sea that once spanned what is now Egypt, approximately 41 million years ago.

A multinational group of researchers, predominantly from Egypt, has unveiled a significant find: a previously unknown species of ancient whale, named Tutcetus rayanensis. This creature swam the waters that once covered today’s Egypt approximately 41 million years ago.

Standing out for its small stature, this whale species is the smallest basilosaurid whale identified so far and is among Africa’s most ancient representations of the family.

Basilosauridae, ancient whales that were completely adapted to aquatic life, were pivotal in the evolutionary journey of whales from land to the ocean. They sported adaptations like a streamlined form, a powerful tail, and flippers, all typical of aquatic creatures. They also had residual hind limbs(visible “Legs”), not used for walking but possibly playing a role in mating.

Tutcetus rayanensis, discovered in mid-Eocene rock formations, is crucial for understanding early whale evolution in Africa. The name “Tutcetus” pays homage to the iconic Egyptian Pharaoh Tutankhamun and the Greek term for whale, “cetus.”

This name choice also marks a century since King Tutankhamun’s tomb discovery and aligns with the imminent inauguration of the Grand Egyptian Museum in Giza. The species descriptor, “rayanensis,” points to its discovery site: Wadi El-Rayan in Fayum.

Hesham Sallam, a leading expert in vertebrate paleontology and the project’s spearhead, shared, “Whales’ evolution from land-dwelling animals to beautiful marine creatures embodies the marvelous adventurous journey of life”. He continued: “Tutcetus is a remarkable discovery that documents one of the first phases of the transition to a fully aquatic lifestyle that took place in that journey”.

The primary specimen showcases portions of the whale’s skull and skeletal features, encased in dense limestone. Tutcetus’s size is estimated at 2.5 meters, weighing around 188 kilograms, making it the tiniest basilosaurid known.

Research on this discovery was featured in Communications Biology. Mohammed Antar, the main contributor, noted the importance of Tutcetus in showcasing the diverse sizes of basilosaurid whales from the Eocene era. He believes further studies might reveal even older whale fossils in Fayum.

“Tutcetus significantly broadens the size range of basilosaurid whales and reveals considerable disparity among whales during the middle Eocene period.”

“The investigation of the older layers in Fayum layers may reveal the existence of an older assemblage of early whale fossils, potentially influencing our current knowledge of the emergence and dispersal of whales.”

Sanaa El-Sayed, a budding researcher, highlighted the significance of Tutcetus’s relatively small stature, linking it possibly to ancient climate changes, like the Late Lutetian Thermal Maximum. She emphasized the whale’s role in understanding early marine adaptations of the species.

“The relatively small size of Tutcetus (188 kg) is either primitive retention or could be linked to the global warming event known as the “Late Lutetian Thermal Maximum (LLTM). This groundbreaking discovery sheds light on the early evolution of whales and their transition to aquatic life.”

By utilizing CT scans to closely examine the teeth and bones of Tutcetus, the researchers successfully pieced together its growth and evolutionary progression. This method yielded a unique perspective on the life cycle of primitive whales. Tutcetus’s quick dental maturation and diminutive size indicate an accelerated life cycle during the early stages of whale evolution.

The discovery of Tutcetus sheds light on the early triumphs of basilosaurids in marine habitats, emphasizing their dominance over semi-aquatic predecessors and their adaptability in exploring new ecological niches once their connection to land ended. Evidence points towards these evolutionary shifts predominantly taking place in subtropical regions.

The research outcomes highlight the expansive geographical dispersion of basilosaurids, suggesting their colonization of the Southern Hemisphere and presence in high latitudes by mid-Eocene.

The findings were published today in the journal Nature.

Image Credit: Hesham Sallam – Mansoura University Vertebrate Paleontology Center