Spenias

Spenias is a genus of extinct ray-finned fish that lived during the Early Triassic epoch. Fossils of Spenias have been found in deposits dating back approximately 250 million years, making them some of the earliest known teleost fish. The genus is primarily known from the Besano Formation in Italy, a lagerstätte that has yielded a rich and well-preserved fossil record of marine life from the Early Triassic.

The type species, Spenias retusus, was described by Louis Agassiz in 1844. Spenias were relatively small fish, typically measuring only a few centimeters in length. Their bodies were elongated and streamlined, suggesting they were active swimmers. Key diagnostic features include the arrangement of their scales, the shape of their fins, and the morphology of their skull and jaw. While detailed anatomical studies are limited due to the fossilization process, available evidence points to a diet consisting of small invertebrates.

The discovery of Spenias and other contemporaneous fish species in the Besano Formation has provided crucial insights into the recovery and diversification of marine ecosystems following the Permian-Triassic extinction event, the most severe extinction in Earth's history. Spenias represents an early branch of teleost evolution, a group that would eventually come to dominate the world's oceans. The limited number of specimens and their fragmentary nature mean that much about the biology and evolutionary relationships of Spenias remains speculative, awaiting further discoveries.