Ancient Crocodile From Sphinx’s Rock Formation Misidentified For A Century

CT Scans Give Ancient Egyptian Crocodile a New Name and a New Place on the Family Tree

A crocodile skull collected east of Cairo, from the same rock formation the Great Sphinx was carved from, sat in a German museum for nearly a century under the wrong name. Its label tied it to the false gharial, a long-snouted, endangered crocodile that survives today in Southeast Asia. A new analysis says that label was wrong, and the fossil now carries a new name, Herugavialis.

A study in Royal Society Open Science centers on that skull, which came from Egypt’s Mokattam Formation, a marine limestone laid down more than 40 million years ago. A researcher named Müller called it Tomistoma cairense in 1927, grouping it with the false gharial because of similarities he noticed. Only the genus, the broader group a species is filed under, has changed. The species name survives with a small spelling change, now cairensis, paired with Herugavialis, a nod to Heru, the Egyptian god also known as Horus, who is often linked to the Sphinx.

Beyond the renaming, the study maps out gharial-like crocodiles that once lived in and around the ancient Mediterranean, then dropped out of the fossil record for millions of years before eventually returning.

Ancient Crocodile Skull Stayed Undescribed While Similar Fossils Were Reclassified

Other fossils got the same treatment. Scientists lumped many extinct crocodiles from Europe, Africa, and Asia into Tomistoma because they resembled the false gharial. Recent family-tree analyses, which compare physical traits across species to map who is related to whom, showed that most of these fossils sat far from the false gharial. Some have since been moved into different genera. The same analyses flagged the Egyptian skull as a poor fit, yet it kept the name, its anatomy undescribed since 1927.

A team of six researchers from the United Kingdom, Sweden, Germany, Egypt, and the United States took a fresh look. The starting point was the original skull, a long, narrow-snouted specimen held at a museum in Stuttgart, Germany, along with several other specimens Müller assigned to the species, including pieces of jaw, all collected at the same Egyptian site. The researchers compared bone shapes with other gharial relatives, especially two Egyptian species of similar age. A micro-CT scanner, which stacks many X-ray images into a 3D model, let the team look inside the skull without damaging it. One of those Egyptian species got a 3D surface scan for comparison.

CT Scans Show Ancient Crocodile Had Telescoped Eye Sockets, Blunt Brain Peak

Differences from those Egyptian species started with the eyes. Herugavialis had eye sockets with strongly raised rims, a shape paleontologists call “telescoped.” Both Egyptian species have raised edges around the eye too, but not telescoped ones.

Inside the skull, CT data showed a blunt peak on a digital mold of the brain cavity, a feature the authors say has not been seen in any other gharial relative. A few more distant crocodile relatives do have one.

In a computer analysis that scored 331 physical features across 152 crocodile types, living and extinct, Herugavialis did not group with the false gharial in either of the two versions the team ran. It also stayed apart from other African and Mediterranean fossils, including the Egyptian species scanned for comparison, despite coming from roughly the same time and place. Instead, it landed on a relatively early branch of the line leading to the living Indian gharial. Its exact spot is less certain, since earlier studies have placed it differently, but the separation from the false gharial held up. That consistency was enough for the team to formally name a new genus.

Mediterranean Crocodile Fossils Vanish for Millions of Years

Placing Herugavialis alongside its relatives showed how varied the region’s gharial family was. Unlike today’s freshwater false gharial, these extinct relatives frequented coastal and shallow sea waters. Between about 66 and 34 million years ago, researchers count at least six gharial relatives from what is now Morocco, Egypt, and Italy. Starting roughly 20 million years ago, at least six more are known from Egypt, Libya, Austria, Malta, Portugal, and Italy.

In between, across most or possibly all of a stretch called the Oligocene, roughly 34 to 23 million years ago, no gharial relatives turn up anywhere in the Mediterranean. The authors say the gap could partly reflect sampling bias, meaning too few digs or poorly preserved sites. They also see evidence from the family tree that it may be a real decline, possibly tied to global cooling and falling sea levels that shrank the coastal habitat these crocodiles needed. Warmer conditions and rising seas may later have allowed a rebound.

By about 5 million years ago, gharial relatives had vanished from the region entirely. The authors say a major episode called the Messinian Salinity Crisis, when the Mediterranean largely dried out, may have played a role.

Filing a fossil under a familiar modern name made the Mediterranean’s crocodile story look smaller than it was. Herugavialis is one correction, and the authors note that other Mediterranean species still need the same re-evaluation before that history can be told straight.

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