Marchesius

Marchesius is a genus of extinct ray-finned fish that lived during the Early Cretaceous period. Fossils of Marchesius have been found in what is now Europe. The genus was first described by the paleontologist Louis Agassiz in 1843.

Marchesius is characterized by its relatively deep body and a single, long dorsal fin. Its scales are cycloid, meaning they are small and rounded with smooth edges. The teeth of Marchesius were conical and pointed, suggesting a diet of small invertebrates or other small fish. The exact placement of Marchesius within the ray-finned fish phylogeny has been debated, but it is generally considered to belong to the order of Clupeiformes, which includes modern-day herrings and sardines.

Fossil specimens of Marchesius are often found in fine-grained sedimentary rocks, indicating deposition in calm water environments such as lakes or lagoons. The discovery of Marchesius contributes to our understanding of freshwater and brackish water fish diversity during the Cretaceous. The genus is named after the Marchesi family, who were patrons of science in the region where the first specimens were discovered. Research on Marchesius continues to shed light on the evolution and paleoecology of ancient fish communities.