CT scans of a fossil found near Cairo show the animal was not a relative of the false gharial (Tomistoma schlegelii), as paleontologists long thought.
The Sphinx was carved from the same rock formation that yielded the Herugavialis cairensis fossil, and both are missing the tip of the nose. Image credit: Karim Zanaty.
“The gavialid crocodylian, Tomistoma is represented by one extant species, Tomistoma schlegelii, the false gharial, which is restricted to freshwater environments in southeast Asia and classified as Endangered based on the IUCN Red List,” said University College London’s Professor Philip Mannion and colleagues.
“By contrast, a large number of Cenozoic fossil species have historically been assigned to this genus, such that the fossil record implies a greater diversity and broader past distribution of Tomistoma, extending its stratigraphic range back to the Eocene and its geographic range to Africa and Europe.”
“Tomistoma cairense, from the Middle Eocene of Egypt, which is one of the stratigraphically oldest taxa to be assigned to the genus.”
“First described in 1927, it is known from several specimens, including the fairly complete holotype skull Staatliches Museum für Naturkunde Stuttgart (SMNS) 10575.”
The authors used micro-CT scanning to peer inside the SMNS 10575 skull and reconstruct its internal anatomy.
They also compared it with other gavialoids, the group that includes the false gharial and the Indian gharial.
They then ran an evolutionary analysis covering 152 species and 331 anatomical characters.
The results placed the Egyptian fossil among the gavialoids, but not near the false gharial.
Now named Herugavialis cairensis, it was an early-branching member of the gavialine lineage, outside the group containing the living Indian gharial and its relatives.
Its features include a long, narrow snout making up about 64% of the skull’s length, and eye sockets with raised rims.
The researchers also looked at the wider story of gavialoids around the Mediterranean.
At least six species existed in the region during the Paleogene period, and at least six more in the Miocene, but none are known from the Oligocene in between.
Alongside other crocodylians in this region, Mediterranean gavialoids appear to have declined in the Late Miocene and had disappeared entirely prior to the Pliocene, with their extirpation possibly driven by the Messinian salinity crisis.
“Throughout much of the last 50 million years, the Mediterranean region hosted a high diversity of crocodiles, including gavials,” said Dr. Paul Burke, also from University College London.
“However, this diversity fluctuated over time, seemingly corresponding to changes in global temperature and sea level, before the loss of all crocodiles in this region as a result of the drying of the Mediterranean approximately 6 million years ago.”
The team’s paper was published today in the journal Royal Society Open Science.
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Paul M.J. Burke et al. 2026. Cranial anatomy of the Middle Eocene Egyptian crocodylian Herugavialis cairensis provides new insights into gavialoid diversity in the Mediterranean region. R. Soc. Open Sci 13 (10): 261173; doi: 10.1098/rsos.261173
