Researchers identify new prehistoric crocodile Herugavialis cairensis in Sphinx quarry rock

Fossil reassessment and CT imaging

An international team of paleontologists led by Paul Burke of the Swedish Museum of Natural History has identified a new extinct crocodile genus, Herugavialis cairensis. The primary specimen, a fossilized skull excavated during the 1920s in Egypt, had been classified in 1927 under the genus Tomistoma, which comprises modern false gharials. Using computed tomography scans, researchers compared more than 300 morphological data points on the shape and size of the skull against living and extinct crocodylians. The findings, published in Royal Society Open Science, showed that the specimen represented a distinct evolutionary branch rather than a relative of modern Southeast Asian false gharials located 5,000 miles away.

This fossil has been flagged as being problematic because it was given the same genus name as one of the extant species.

Naming and anatomical characteristics

The newly designated genus takes its name from Heru, also known as Horus, an ancient Egyptian deity associated with the Great Sphinx of Giza. Researchers selected the name due to a physical parallel: the fossil skull lacks the tip of its snout, mirroring the damaged nose of the stone Sphinx. Herugavialis cairensis possessed a long, narrow snout lined with razor-sharp teeth, alongside elevated eye sockets that protruded above the skull roof in a manner similar to modern Indian gharials. Dr. Burke noted that these physical adaptations served an aquatic, fish-eating lifestyle in coastal waters.

Razor-sharp teeth, alongside the long and thin snout, would have been adapted for catching fish. The Mokattam Formation, where Herugavialis comes from, preserves fossils of several species of bony and cartilaginous fish, which Herugavialis probably fed on.

Prehistoric marine ecosystem in Egypt

The fossil originates from the Mokattam Formation, an Eocene limestone layer located southeast of Cairo dating between 45 million and 54 million years ago. At the time Herugavialis lived, shallow marine waters covered much of northern Egypt, supporting diverse populations of primitive whales, sharks, bony fishes, and at least two other crocodylian species. Herugavialis cairensis represents one of six gharial species known to inhabit the Mediterranean region across a 43-million-year span between 66 million and 23 million years ago. Crocodylians subsequently disappeared from the Mediterranean basin approximately 6 million years ago during the desiccation of the sea.

Potential fossils within Giza limestone

The geological formation holding the crocodile fossils is the identical stone layer quarried millennia later to construct the Great Sphinx and the Giza pyramids. Paleobiologist Philip Mannion from University College London noted that prehistoric marine organisms remain embedded throughout the quarried blocks of the Giza plateau. Dr. Burke acknowledged that additional fossil specimens of prehistoric animals might sit within the body of the Sphinx itself, though researchers cannot dismantle the monument to verify them. Mannion explained that detailed study of century-old museum archives continues to uncover previously uncharacterized ancient vertebrate species.

It was already known and recognized as something distinct, but more detailed research was needed to determine exactly what it represented.