Â鶹ÒùÔº

In a recent study, a research team led by Martin Ebert from the Ludwig Maximilian University and Adriana López-Arbarello from the Unidad Ejecutora Lillo examined fossil fish specimens of the family Caturidae housed in various museums and institutes to identify a new species.

Caturoids are an extinct, fast-swimming predatory fish of medium size (10–40 cm) known to have had their largest geographic distribution in the Jurassic, with 14 known species having lived then. They eventually went extinct in the Lower Cretaceous, from which only three species are known.

In their study in the Swiss Journal of Palaeontology, Ebert and López-Arbarello aimed to study the morphology and taxonomy of Caturidae.

They were ultimately able to determine that 33 of the analyzed fossils belonged to a new species of Caturus, collected in the Upper Jurassic Plattenkalk basins of the Solenhofen Archipelago in Bavaria, Germany, and from the Nusplingen Plattenkalk of Baden-Württemberg, Germany.

The new species is called Caturus enkopicaudalis sp. nov., which combines the Greek word for notch εγκοπή (enkopí) and the word caudalis in reference to its caudal fin (tail fin), features which are remarkably unique in the new species.

At first sight, Caturus enkopicaudalis sp. nov differs from other Caturidae by the peculiar shape of the caudal fin as well as the high number of scale rows.

The caudal fin, unlike other Caturus species, was large and forked with a distinctive 'double emarginate' shape with a central plateau. The two unusual notches create a stepped profile unlike the typical forked tails of other Caturus species.

The central plateau is typically made up of three, in one case, four, short and broad central rays.

Exactly how this unique tail may have helped the new Caturus species is unclear, Prof. David Bellwood, a colleague of Ebert, speculates, "I suspect it was an evolutionary innovation that did not stand the test of time.

"There are two-tailed deformities but I suspect yours is natural—I can see of no huge advantage—it would help sudden acceleration by decreasing the aspect ratio and thus increasing thrust—but it would come at the expense of losing the energetic benefits of the forked caudal.

"I would guess either a) the plesiomorphic condition for the lineage is forked and that this species had a new prey/location that needed more burst acceleration or b) it was just a spontaneous maladaptation that this species could cope with for a while."

The second distinctive features that differentiate Caturus enkopicaudalis sp. nov from other species at first sight are the high number of scale rows and the thick ganoid scales covering the back half of the caudal fin rays.

Typically, Caturus species exhibit between 51 and 56 scale rows counted from the "shoulder" to the back fin. However, Caturus enkopicaudalis sp. nov has a total of 91–99 rows. These scales are relatively small and smooth with straight back edges and no discernible patterns on their surfaces.

It is likely that the high number of scales per row and scale rows can be attributed to their small size. Additionally, it is the only Caturus species from the Upper Jurassic with unordered ganoin scales.

Many of its other features are characteristic of caturids, including an extremely slender and rod-like maxilla (upper jaw), which is typical of caturids. It bore 33 small pointed teeth while the dentary (lower jaw) had 25, with two being three times longer than the maxillary teeth. This makes its teeth typically larger and broader than those of other caturids.

Its gular plate (a ventral bony plate between the dentary in some primitive fish), however, is among the widest of all caturids.

The discovery adds to the known remarkable diversity that the Caturus species exhibited during the Jurassic. Further research will likely identify many new fish species, including caturids, aiding us in our understanding of early marine life.

© 2025 Science X Network