# Researchers reclassify 45-million-year-old Egyptian crocodile skull as Herugavialis cairensis

- Published: 2026-11-07 09:37 UTC
- Section: Life & Health › Biology & biochemistry
- Tags: Herugavialis cairensis, Tomistoma cairense, Mokattam Formation, Gavialoidea phylogeny, fossil crocodylian, skull CT scan
- URL: https://realtech.media/news/rt-4fed274a7a8769ac455a1893_researchers_reclassify_45/

**Computed tomography scans and phylogenetic analysis resolved the century-old misclassification of a Middle Eocene gavialoid from the Mokattam Formation.**

![Researchers reclassify 45-million-year-old Egyptian crocodile skull as Herugavialis cairensis](https://realtech.media/media/2026/11/f5e60513dd89339f.jpg)
*Earth.com*

An international research team led by the Swedish Museum of Natural History and University College London has formally reassigned an Eocene crocodylian fossil to a new genus, *Herugavialis*. The specimen, originally excavated near Cairo from the Middle Eocene Mokattam Formation, was evaluated using computed tomography scans alongside a phylogenetic analysis of 152 species across 331 anatomical characters, according to a study published in *Royal Society Open Science* [1].

Historically discovered around 100 years ago and described in 1927, the holotype skull—which lacks the tip of its snout—was initially cataloged as *Tomistoma cairense*. The Middle Eocene Mokattam Formation, dated to approximately 45 million years ago, consists of marine limestone, the same rock layer from which the Great Sphinx was carved. The fossil material, curated at the State Museum of Natural History Stuttgart in Germany, includes a skull and referred jaw fragments that may originate from a single individual [1].

## Computed tomography and cranial morphology

Computed tomography allowed the researchers to reconstruct the endocranial cavity and examine features previously obscured by the matrix. The digital endocast revealed an atypical blunt dorsal projection not observed in other members of Gavialoidea. Morphometric analysis established that the snout accounts for roughly 64 percent of total skull length [1].

Additionally, the skull possesses elevated, telescoped orbital margins that rise noticeably above the cranial roof. These anatomical differences distinguish the fossil from extant false gharials (*Tomistoma schlegelii*), the modern Indian gharial (*Gavialis gangeticus*), and other roughly contemporaneous Egyptian gavialoids, including *Eogavialis africanum* and *Paratomistoma courti* [1].

## Phylogenetic placement and Mediterranean climate shifts

Phylogenetic reconstruction under maximum parsimony demonstrated that the species does not cluster within the genus *Tomistoma* or with other local Mediterranean taxa. Instead, *Herugavialis cairensis* resolved closer to *Gavialis gangeticus*, indicating a separate evolutionary lineage within Gavialoidea [1].

Historical diversity data show that the Mediterranean basin hosted at least six gavialoid species during this period, followed by an apparent diversity decline in the Late Eocene and Oligocene. The researchers suggest global cooling and dropping eustatic sea levels shrank available coastal habitats, followed by a potential Miocene recovery and the final extirpation of regional crocodylians linked to the Messinian Salinity Crisis roughly 6 million years ago [1].

## Sources

1. [Royal Society Open Science](https://doi.org/10.1098/rsos.261173)
2. [Earth.com](https://www.earth.com/animals/a-fossil-crocodile-skull-missing-its-snout-just-like-the-great-sphinx-finally-got-its-own-name-after-a-century)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-4fed274a7a8769ac455a1893_researchers_reclassify_45/