Calodiscus is a genus of Eodiscinid trilobite in the family Calodiscidae.KOBAYASHI T. 1943. Brief notes on the Eodiscids 1, their classification with a description of a new species and a new variety, Proceedings of the Imperial Academy, Tokyo, Volume 19, pp. 37-42. It lived during the late Lower Cambrian, with remains found in Canada (Newfoundland & Labrador), the United States (Massachusetts, New York State), Greenland, The United Kingdom (England), Sweden, France, Germany, Italy (Sardinia), Kazakhstan, the Russian Federation and China.
The type species by original designation is Agnostus lobatus Hall, 1847 from the upper part of the lower Cambrian Browns Pond Formation (formerly Schodack Formation) at Troy in the Taconic region of New York State, USA [= Calodiscus korolevi Pokrovskaya in Ergaliev and Pokrovskaya, 1977; Calodiscus lakei Rasetti, 1952; and Calodiscus n. sp. A of Geyer, 1988, according to Cederström et al., 1988].HALL, J. 1847. Palaeontology: Volume 1. Containing descriptions of the organic remains of the lower division of the New-York System. Natural history of New York, Albany. 338 pp.CEDERSTRÖM, P., AHLBERG, P., CLARKSON, E. N. K., NILSSON, C. H. and AXHEIMER, N. 1988. The Lower Cambrian eodiscoid trilobite Calodiscus lobatus from Sweden: Morphology, ontogeny and distribution. Palaeontology, Vol. 52, Part 3, 2009, pp. 491 – 53.
Lochman (1956)LOCHMAN, C. 1956. Stratigraphy, paleontology, and paleogeography of the Elliptocephala asaphoides strata in Cambridge and Hoosick Quadrangles, New York. Bulletin of the Geological Society of America, 67, 1331 – 1396. demonstrated that Calodiscus agnostoides (Kobayashi, 1943) represents late meraspid instars of C. lobatus (Cederström et al., 1988, p. 500).
Of four named Calodiscus species from the Lower Cambrian of the Siberian Platform revised by Korovnikov and Bushuev (2024)KOROVNIKOV, I.V., BUSHUEV, E.V. 2024. Revision of the Trilobite Genus Calodiscus Howell, 1935 (Siberian Platform). Paleontol. J. 58, 684–696. only two, C. resimus Repina, 1972 and C. schucherti (Matthew, 1896) were retained in the genus. C. helena (Walcott, 1889)WALCOTT, C.D., 1889. Description of new genera and species of fossils from the Middle Cambrian, Proc. U.S. Nat. Mus. 11 (738), pp. 33–46. and C. granulosus Jegorova et Shabanov, 1972 (Korovnikov and Bushuev, op cit.) were considered significantly different to assign them a new genus, Paracalodiscus, within the family Weymouthiidae Kobayashi, 1943.
The generic homonym Calodiscus, as described by Rabenhorst in 1853,RABENHORST, L. 1853. Die Süsswasser-Diatomaceen (Bacillarien.): für Freunde der Mikroskopie. pp. -xii, -72, 10 plates [I–X]. Leipzig: Eduard Kummer. is a genus of freshwater diatom. However the type species, Calodiscus superbus, has been reclassified as Campylodiscus superbus (Rabenhorst).VANLANDINGHAM, S.L. (1968). Catalogue of the fossil and recent genera and species of diatoms and their synonyms. Bacteriastrum through Coscinodiscus Part 2. pp. 494-1086. Lehre: J. Cramer.
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