New genus and species of the Simotoidan isopod, which lived in the early Cretaceous period, have been identified from two well-conserved specimens found in Lebanon. Originating from the environment of freshwater lakes, this isopod provides an unconventional perspective on the evolutionary origins of Simotoids inhabiting living caves and groundwater.

Dysopodus gezei He lived in a shallow freshwater lake in Lebanon (Epoch of the early Cretaceous period) about 125 million years ago.

This creature had an elongated body and was more than twice its width (total length 1.8-2.5 cm).

That was a type Isopodorder of crustaceans, including both aquatic and locally populated species.

“Isopoda is a diverse group of Malacostracan crustaceans, including more than 10,000 described organisms,” said Dr. Mario Södel, a paleontologist at the Senkenberg Centre at the University of Tenbingen, and his colleagues.

“Most living species lie in a variety of marine environments ranging from deep waters to sandy beaches and rocky coasts.”

“Isopoda can be considered primarily as a marine group, and it is most likely that the latest ancestor of all isopods is ocean.”

“But there are also many isopods that live outside the marine realm.”

“The species-rich group of isopodas – oniscidea – houses over 3,800 species, most of which live in a variety of fully terrestrial habitats.”

“Apart from the marine and terrestrial environments, isopods also live in brackish and freshwater environments, with about 1,000 described species living in freshwater.”

“Isopods have freshwater habitats colonized in multiple independent habitats, with a wide variety of different species in freshwater habitats, ranging from old to in some cases highly species-rich groups to single phylogenetically isolated species.”

Dysopodus gezei There were strong similarities to the living non-parasitic strains of Cirolanidaea group of isopods within subordered Shimotoida.

“The Shimotoida is a group of isopods that contain scavengers, predators, microrelets and parasites,” the paleontologist said.

“In this, finely repaired and parasitic species can form natural groups.”

“With Timotoida, many freshwater species are parasites that are likely to enter freshwater habitat along with hosts, either fish or crustaceans.”

“There are many representatives of Shimotoida (Shimotoida people – not confused with Shimotoids) throughout their lifetimes that are neither micropredata nor parasites.”

“These are often referred to as Cirolanidae, a group of morphologically distinct isopods.”

Dysopodus gezeiholotype. Image credits: Shadell et al. , doi: 10.1098/rsos.241512.

Two specimens of Dysopodus gezei It was excavated in Lebanon in 2003 and 2023.

“The specimen was found at the Lebanese Disol in Jdeidet Bkassine,” the researchers said.

“These layers correspond to finely stacked, organically rich deposits harvested in five mining areas within the Grace Duriban Alloformation, one in the north of Lebanon, one in the center, and three regions in southern Lebanon.

“All evidence shows a series of small shallow lakes and marsh areas near the volcanic buildings.”

The rarity of living freshwater silolanide species emphasizes the importance of discovery Dysopodus gezei As an extinct species that supports true freshwater archaeological fabrics, it not only has its history of evolution on earth, but also of the evolution of underground freshwater species.

“The discovery of new fossils represents the rare discovery of fossil isopods from freshwater habitats,” the scientist said.

“This places a new perspective on the origins of the existing non-parasitic freshwater simotoid people.”

“This finding does not disprove the colonization of cave and groundwater habitats through the cutting of underground species by regressing coastlines, but the presence of freshwater Simotoids in the eastern Tethian region during the early Cretaceous period gives a different light to the origins of living freshwater animals.”

“Additional specimens of this species may provide more morphological details, as they may maintain fine morphological details, and can then be used to draw more accurate conclusions between Cretaceous freshwater species and existing cave and groundwater fauna.”

Survey results Published in the April 2025 issue of the journal Royal Society Open Science.

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Mario Shadell et al. 2025. Freshwater isopods from 125 million years ago shed new light on the origins of underground freshwater species. R. Soc. Open SCI 12(4): 241512; doi: 10.1098/rsos.241512