Gyrosteus is an extinct genus of very large ray-finned fish belonging to the family Chondrosteidae.[3] 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 | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | †Chondrosteiformes |
| Family: | †Chondrosteidae |
| Genus: | †Gyrosteus Agassiz, 1843 |
| Type species | |
| †Gyrosteus mirabilis [2] Agassiz 1844 | |
| Species | |
| |
Fossil remains of G. mirabilis have been recovered from the Whitby Mudstone Formation, United Kingdom, and from Ahrensburg erratics assemblage in Schleswig-Holstein, northern Germany.[4] It was mentioned but not formally described in subsequent publications and was left as a nomen nudum for more than 25 years.[5] Then in 1889 it was featured and formally described by Arthur Smith Woodward.[6] Gyrosteus was thought to be exclusive of the “British faunal province” and separated from the “Germanic faunal province” until the discovery of a hyomandibula in the baltic realm, mostly populated by Germanic fauna, which possibly implicates that Baltic region represented an interdigitating zone between both regions.[4]
The members of the genus Gyrosteus were massive fishes, with a maximum calculated standard length of 6 metres (20 ft) to 7 metres (23 ft), and with a reported hyomandibula reaching 50 centimetres (20 in).[7]
