Media release

From: Springer Nature

New ancient miniature whale species identified 

The fossilised remains of a new species of basilosaurid — an extinct family of fully aquatic whales  — are described in a study published in Communications Biology. The whale, which is estimated to have been 2.5 metres long, is thought to be the smallest known basilosaurid and has been named Tutcetus rayanensis after the ancient Egyptian Pharaoh, Tutankhamun.

Mohamed Anter, Hesham Sallam, and colleagues discovered skull, jaw, teeth and vertebrae fragments — dating to around 41 million years ago — belonging to the new species in the Fayum Depression, Egypt. They suggest that the whale was near adulthood, but had not reached full adulthood, as the bones within its skull and vertebrae had fused together and its permanent teeth were at an advanced stage of emergence — with its permanent molars having emerged before its anterior premolars, incisors, and canines. As previous research has proposed that the emergence of permanent molars before permanent premolars tends to occur in mammals with shorter life cycles, this could indicate that Tutcetus reached sexual maturity at an earlier age and died at a younger age than other basilosaurids. Based on the dimensions of the remains, the authors estimate that Tutcetus was approximately 2.5 metres long and had a body mass of around 187 kilograms. As previously identified basilosaurids range from four to 18 meters in length, this makes Tutcetus the smallest known whale in this family to date.

The authors speculate that the smaller body size of Tutcetus, compared to other basilosaurids, may have evolved in response to a warming event — known as the Lutetian thermal maximum — that occurred around 42 million years ago. Previous research has suggested that animals tend to evolve smaller body sizes in warmer climates. Together, the findings provide further insight into basilosaurid evolution.