A Century Ago, an Extinct Crocodilian's Skull Was Found in the Rocks That Built the Sphinx. Turns Out, It Belonged to a New Species

Around 4,500 years ago, ancient Egyptians carved the Great Sphinx of Giza out of limestone in the Mokattam rock formation. Little did they know, the material they were digging through preserved something even more archaic: fossils of a long-extinct crocodile. Researchers have identified a previously unknown species of gavial, a type of crocodilian with a long, thin snout, from a fossil originally found in the rock formation that the ancient Egyptians sculpted into the Sphinx and the Pyramids of Giza.

The new identification corrects a previous erroneous classification, according to a study published October 7 in the journal Royal Society Open Science. It also sheds light on the fauna that existed in what’s now Egypt well before human-made monuments appeared on the horizon. In the 1920s, several fossilized remains, including a largely intact crocodile-like skull, emerged from the roughly 45-million-year-old Mokattam Formation at a site near Cairo.

Because of the bones’ resemblance to those of Tomistoma schlegelii—a living gavial native to Indonesia and Malaysia—experts originally assigned them to the same Tomistoma genus. Until now, the well-preserved skull was the holotype, or name-bearing representative fossil, for the extinct T. cairense. Thanks to modern paleontological techniques like micro-CT scanning, which allows researchers to see inside fossils without breaking them, the team behind the new work found many differences between Tomistoma and the Mokattam Formation crocs.

Comparing measurements of the skull to those of modern and fossil gavials revealed that the roughly 18-inch-long noggin represented not just a new species, but a new genus as well. They named it Herugavialis cairensis, drawing inspiration from the Egyptian god Heru, also known as Horus. Some Egyptian texts call the Sphinx “Horus of the Horizon.” The associations between the H. cairensis skull and the iconic Sphinx go beyond the material that yielded them.

Both are missing the tips of their noses. The origin of the Sphinx’s name The Egyptians did not refer to the great statue as the Sphinx. Rather, ancient Greeks started calling it that around 2,000 years after it was carved.

They possibly did so because of its resemblance to their mythological sphinx, which had a lion’s body, a woman’s head and an eagle’s wings. The Mediterranean region was home to a diverse community of crocodilians, including gavials, during much of the last 50 million years, lead author Paul Burke, a paleontologist at the Swedish Museum of Natural History, says in a statement. In fact, H. cairensis would have shared its shallow marine habitat with at least two other gavial species.