Macrosemiidae

Macrosemiidae is an extinct family of ray-finned fish that lived during the Jurassic and Cretaceous periods. These fish are characterized by their relatively large scales, hence the name "Macrosemiidae" which translates to "large-scaled family." They possessed a deep, laterally compressed body shape and a single, long dorsal fin that often extended along a significant portion of their back. Their pectoral fins were typically short, while their pelvic fins were located ventrally. The caudal fin was usually forked.

Fossils of Macrosemiidae have been discovered in marine and freshwater deposits across Europe, Asia, and North America. Their diet is believed to have consisted of small invertebrates, though specific details are often inferred from their jaw structure and tooth morphology. Macrosemiids are considered to be a basal group within the teleost fishes, meaning they represent an early evolutionary lineage. Their presence in various depositional environments suggests they were adaptable to different aquatic settings. The family includes several genera such as Macrosemius, Notagogus, and Tselfatia. The extinction of Macrosemiidae is thought to have occurred by the end of the Cretaceous period, with their ecological niches likely filled by more derived teleost groups.