Gyrosteus is an extinct genus of a large ray-finned fish belonging to the family Chondrosteidae. It comprises the type species, Gyrosteus mirabilis, which lived during the early Toarcian (Late Early Jurassic) in what is now northern Europe. A possible second species, "Gyrosteus" subdeltoideus, is known from otoliths.
Gyrosteus is an extinct genus of a large ray-finned fish belonging to the family Chondrosteidae. It comprises the type species, Gyrosteus mirabilis, which lived during the early Toarcian (Late Early Jurassic) in what is now northern Europe. A possible second species, "Gyrosteus" subdeltoideus, is known from otoliths.
== Discovery and naming == While seeing fossil collections of the Earl of Enniskillen and Philip Grey Egerton, Louis Agassiz identified fragments of a giant fish (praised by him then as "marine giant") from the Yorkshire Lias in the 1830s, referring them to Coelacanths and naming it "Gyrosteus" without any referred species in 1834, back then a nomen nudum, as he never described or illustrated the materials. His bankruptcy halted the formal description process, with the species only properly named in 1840. Egerton mentioned "Gyrosteus mirabilis" earlier (1837) but did not describe it, leaving Agassiz as the credited author. Simpson misattributed a fragment as a cephalopod in 1855. Arthur Smith Woodward thoroughly described Gyrosteus mirabilis in 1889–90, distinguishing it from Chondrosteus based on dermal bone patterns and branchial structure. A partial skull roof was noted but its elements remained poorly understood, with significant material loss due to pyrite decay.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).