| 词条 | Geisonoceras |
| 释义 |
| fossil_range = Middle Ordovician - Middle Devonian [1] | image = Geisonoceratidae - Geisonoceras species.JPG | image_caption = Fossil of Geisonoceras species | regnum = Animalia | phylum = Mollusca | classis = Cephalopoda | subclassis = Nautiloidea | ordo = Orthocerida | familia = Geisonoceratidae | genus = Geisonoceras | genus_authority = Hyatt, 1884 }} Geisonoceras is an extinct orthocerid genus named by Hyatt, 1884, and type for the Geisonoceratidae established by Zhuravleva in 1959. Fossil recordFossils of Geisonoceras are found in marine strata from the Ordovician until the Devonian (age range: from 460.9 to 383.7 million years ago.). Fossils are known from various localities in Europe, North America and Asia.[1][3] Species
DescriptionShells are elongate, straight or slightly curved, and slowly expanding with a circular or subcircular cross section, transverse aperture and slight hyponomic sinus. The surface has broad transverse bands with fine growth lines between. Sutures are straight, transverse or slightly oblique. The siphuncle is subcentral, necks short and straight, connecting rings slightly expanded into the chambers.[2] References1. ^1 Paleontology Database {{Taxonbar|from=Q16976416}}2. ^1 Walter A Sweet, 1964. Nautiloidea -Orthocerida, Treatise on Invertebrate Paleontology Part K, Endoceratoidea, Actinoceratoidea, Nautiloidea. Geological Society of America and Univ Kansas Press. Teichert and Moore (Eds) 5 : Nautiloids|Middle Ordovician first appearances|Middle Devonian genus extinctions|Paleozoic life of Ontario|Paleozoic life of Quebec |
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