Hoeloceras
Introduction '''''Hoeloceras''''' is an extinct orthoconic nautiloid cephalopod from the upper Ordovician, generally included in the Actinocerida.Nautiloids are a subclass of shelled cephalopods that were once diverse and numerous but are now represented by only a couple of genera, ''Nautilus'' and ''Allonautilus''. ''Hoeloceras'', which has a straight shell with a broadly curved to almost flattened venter on the underside and a more highly arched dorsum on the upper, meeting acutely on either side, was named by Walter Sweet in 1958 (Chen & Liu 1977, Teichert 1964) who first recognized it in Ordovician sediments near Oslo, Norway, and included it in the Actinocerida.Teichert (1964) identified ''Hoeloceras'' as a synonym of ''Lambeoceras'', as the acutely angled dorso-ventral seam suggests. Flower (1968) referred to ''Hoeloceras'' as a "flatfish", in common with ''Lambeoceras'' and ''Gonioceras'', but reassigned it to the Reudemannoceratidae (Discosorida) noting that neither (siphuncular) annuli or parispatium - diagnostic of the Actinocerida - had been observed.Since then specimens identified as ''Hoeloceras'', and retained in the Actinocerida, have been discovered in China (Chen& Liu) and Korea (Yun, Cheol-Soo), where, in Korea, it is associated with the actinocerids, ''Armenoceras'', ''Ormoceras'', and ''Selkirkoceras''.
See also List of nautiloids
References * Teichert 1964, Actinoceratoidea, Treatise on Invertebrate Paleontology Part K, (Nautiloidea) Geological Society of America and University of Kansas Press. pp K208 -K210. * Flower 1968, The First Great Expansion of the Actinoceroids, Memoir 19, Part I, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM. * Chen et Liu, 1977 ''Hoeloceras yimengshanense'' ; Google translation from the Chinese. * Yun, Cheol-Soo, Biogeographical Characteristics of the Ordovician Cephalopods from Korea. * Sepkoski, J.J. Jr. 2002.A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). ''Bulletins of American Paleontology'' '''363''': 1–560.Sepkoski's Online Genus Database (CEPHALOPODA)