Newly Discovered Shallow Water Fish Species in Portugal

Paleontologists have announced the discovery of a new genus and species of Balacromian Ikuchosaur, based on a fossilized skull found in the Agua de Maderos Formation in Portugal.

The newly identified species thrived in the early Jurassic oceans around 193 million years ago.

It has been scientifically designated as Gadusaurus Aqualigneus; this marine reptile is a small Ikchosaur, measuring approximately 2 m (6.6 feet) in length.

“Iktiosaurus was a group of Mesozoic reptiles renowned for their adaptation back to marine life,” explained Dr. Joan Platas et Sousa, a researcher from Nova de Lisboa University.

“These creatures existed from the early Triassic to the late Cretaceous, but early Jurassic fish fauna is most commonly found in the European fossil record.”

“While some western regions are rich in marine deposits, southern areas like the Iberian Peninsula (encompassing Portugal and Spain) have very few and fragmented records.”

The nearly complete skull of Gadusaurus Aqualigneus was found in a planarized state, measuring about 35.2 cm (13.9 inches) in length, in the Agua de Madeiros Formation in 2021.

“The specimens we analyzed were collected in mainland Portugal, specifically in the San Pedro de Moel area,” the paleontologist stated.

“The fossil block was located in the sands of Agua de Maderos Beach, at a stream marking the boundary between Marinha Grande and Alcobaza municipalities.”

“This region lies within the Lusitania Basin, which is situated on the passive margin of Western Iberia in the Atlantic, providing exceptional marine records from the Lower Jurassic,” they added.

“The Lusitania Basin is a long, narrow structure bordered to the east by the Iberia Massif and to the west by the Valiskan Berrenga Horst.”

“The basin’s development coincided with the opening of the Atlantic Ocean, displaying various sedimentary facies from the upper Triassic to the upper Cretaceous.”

Phylogenetic analysis places Gadusaurus Aqualigneus within the Ichthyosaur Clade Baracromia, part of the Neoichthyosaur and Parvipelvia Clades.

“This specimen represents the most complete and well-preserved remains of Uoshima described so far on the Iberian Peninsula,” the researchers noted.

“Moreover, it is the first new species of this marine reptile group documented in Iberia.”

“This specimen predates the Toarcian Marine Anoxia Event, which is believed to have affected the lifestyle of later Ichthiosaurus species.”

“It’s reasonable to assume that ecological events during this period may have similarly influenced the lifestyle of this type, though further studies are essential.”

The discovery of Gadusaurus Aqualigneus will be detailed in a new paper published online in the journal Acta Palaeontologica Polonica.

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J. Platas E. Sousa et al. 2025. A new Ichaosaurus from the lower Jurassic of Portugal (Iberian Peninsula). Acta Palaeontologica Polonica 70(1):179-192; doi:10.4202/app.01199.2024