Just days after the world was introduced to the heaviest known ancient whale, a much tinier member of the same family has been found on the other side of the planet.
The newly discovered species is one of the earliest — and smallest — basilosaurids, a family of ancient aquatic creatures related to modern whales, researchers report August 10 in Communications Biology. It measured just 2.5 meters long, the team estimates, and weighed a mere 188 kilograms, about as much as a blue whale’s heart.
“It’s definitely a very small animal,” says Mark Uhen, a paleontologist at George Mason University in Fairfax, Va., who was not involved in the study.
Researchers found the 41-million-year-old fossilized skull, jaw and teeth of Tutcetus rayanensis in Wadi El-Rayan, a nature reserve in Egypt. Named in part after the Egyptian pharaoh Tutankhamun, the species shares King Tut’s regal roots: The name “basilosaurid” is derived from the Latin basilosaurus, or “king lizard” (the first basilosaurid specimen was mistakenly classified as a reptile).
Like Tutankhamun, the T. rayanensis specimen perished on the cusp of adulthood. It still had a couple of its baby teeth, along with adult molars that grew in relatively early in its life. That pattern of tooth growth suggests that the species “lived fast and died fast,” or at least faster than other basilosaurids, says study coauthor Abdullah Gohar, a paleontologist at Mansoura University in Egypt.
Another group of researchers recently announced the discovery of the basilosaurid Perucetus colossus, possibly the heaviest animal ever known to exist, in Peru (SN: 8/2/23). Just one of its vertebrae weighed over half as much as its teeny cousin’s entire body.
T. rayanensis may have lived around the same time as the gigantic P. colossus, which rivaled modern blue whales in body mass, Gohar says. But their vastly different body types indicate that they probably occupied different ecological niches, Uhen says.
Gohar says he hopes to study older fossils to better understand the full story of whale evolution. The area where the researchers found T. rayanensis contains 15 million years of mammalian evolutionary history, including that of other early whales.
“We’ve been working that area for a long time,” Uhen says. “It’s good to know that there are still things out there to discover.”