{{Short description|Extinct genus of gastropods}} {{Automatic taxobox | fossil_range = Pliensbachian-Aalenian<br />~{{fossilrange|188|170|earliest=Hettangian}} | image = | image_caption = Life restoration | parent_authority = Gründel & Nützel, 2013 | taxon = Coelodiscus | authority = Broesamlen, 1909 | subdivision_ranks = Species | subdivision = *''Coelodiscus minutus'' *''Coelodiscus biumbilicatus'' *''Coelodiscus fluegeli'' *''Coelodiscus wrightianus'' }}
'''''Ceolodiscus''''' is an extinct genus of gastropod from the Lower and Middle Jurassic of Europe, mostly on Germany, France and United Kingdom.<ref name="coelodiscus" /><ref>{{Cite journal |last1=Bandel |first1=Klaus |last2=Hemleben |first2=Christoph |date=1987-02-11 |title=Jurassic Heteropods and their Modern Counterparts (Planktonic Gastropoda, Mollusca) |url=http://dx.doi.org/10.1127/njgpa/174/1987/1 |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=174 |issue=1 |pages=1–22 |doi=10.1127/njgpa/174/1987/1 |issn=0077-7749|url-access=subscription }}</ref><ref>{{Cite journal |last1=Schulbert |first1=C. |last2=Nuetzel |first2=A. |date=2013 |title=Gastropods from the Early/Middle Jurassic transition of Franconia (Southern Germany) |url=https://www.researchgate.net/publication/259890840 |journal=Bulletin of Geosciences |volume=88 |issue=4 |pages=723–778}}</ref> Other posible records include specimens from Hungary of Earliest Jurassic (Hettangian) age.<ref>{{Cite journal |last=Szente |first=I. |date=1992 |title=Early Jurassic Molluscs from the Mecsek Mountains (S. Hungary. A preliminary study. |url=https://edit.elte.hu/xmlui/bitstream/handle/10831/42771/013.pdf |journal=Annales Univ. Budapest. Sectio Geologica |volume=29 |issue=1 |pages=324–343}}</ref> As well there are specimens from Switzerland of Middle Jurassic age.<ref>{{Cite journal |last=Etter |first=Walter |date=1996 |title=Pseudoplanktonic and benthic invertebrates in the Middle Jurassic Opalinum Clay, northern Switzerland |url=http://dx.doi.org/10.1016/s0031-0182(96)00036-3 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=126 |issue=3–4 |pages=325–341 |doi=10.1016/s0031-0182(96)00036-3 |issn=0031-0182|url-access=subscription }}</ref> It is the only genus in the monotypic family '''Coelodiscidae'''.<ref name="WoRMS">{{cite WoRMS|title=Coelodiscidae|id=1611336|accessdate=19 November 2024}}</ref> The genus is usually allied with modern Pterotracheoidea, based mostly on its resemblance with modern ''Atlanta'' larvae, yet it differs by lacking extant family affiliations.<ref>{{Cite web |last1=Wall-Palmer |first1=Deborah |last2=Janssen |first2=Arie W |last3=Goetze |first3=Erica |last4=Choo |first4=Le Qin |last5=Mekkes |first5=Lisette |last6=Peijnenburg |first6=Katja T. C. A. |date=2020-03-21 |title=Fossil-calibrated molecular phylogeny of atlantid heteropods (Gastropoda, Pterotracheoidea) |url=http://dx.doi.org/10.21203/rs.3.rs-18183/v1 |access-date=2024-11-20 |doi=10.21203/rs.3.rs-18183/v1 }}</ref> This genus is linked with the Toarcian Oceanic Anoxic Event, that likely triggered its evolution.<ref name="coelodiscus" />
The shell is small but stocky; involute or with a slightly protruding spire. Whorls are generally smooth, evenly rounded and slightly overlapping; umbilicus deep, aperture ovate.<ref name="coelodiscus">{{Cite journal |last1=Teichert |first1=Sebastian |last2=Nützel |first2=Alexander |date=2015 |title=Early Jurassic anoxia triggered the evolution of the oldest holoplanktonic gastropod Coelodiscus minutus by means of heterochrony |journal=Acta Palaeontologica Polonica |doi=10.4202/app.00145.2014 |issn=0567-7920|doi-access=free }}</ref> Is the oldest known holoplanktonic gastropod, thanks to a bilateral symmetrical shells as an adaption to active swimming. Beyond the most common of the sea snails of the Posidonienschiefer Formation, it is also one of the most varied in size terms.<ref name="coelodiscus" /> It has been related to large floating driftwood as one of the primary settlers.<ref name="coelodiscus" />
==References== {{Reflist}} *J. B. Knight ''et al''. 1960. Systematic descriptions; Treatise on Invertebrate Paleontology, Part I, Mollusca (1):''I''196. *[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=9668 Coelodiscus]
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Category:Gastropod genera Category:Euomphalidae Category:Jurassic gastropods Category:Jurassic animals of Europe Category:Fossil taxa described in 1909
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