The Ellimmichthyiformes, also known as double-armored herrings, are an extinct order of ray-finned fish known from the Late Jurassic to the Oligocene. They were the sister group to the extant true herrings, shad and anchovies in the order Clupeiformes, with both orders belonging to the suborder Clupeomorpha. Some studies suggest that the order may be potentially paraphyletic with respect to crown-group Clupeiformes, although more comprehensive studies support them as being a monophyletic group.
A highly successful group throughout the Cretaceous, they were found worldwide and are known to have inhabited both marine and freshwater habitats. They appear to have been a largely marine group for most of their history, with the first freshwater lineages appearing during the Late Cretaceous. In 2026, the Ancashichthyidae, the earliest known ellimmichthyiforms (and clupeomorphs as a whole), were described from the Late Jurassic of Peru.
The discovery of the Ancashichthyiedae suggests that like many other fish lineages, the Ellimmichthyiformes may have originated around South America. Shortly after the first major radiation of the Ellimmichthyiformes in the Early Cretaceous, the Mediterranean portion of the Tethys Ocean appears to have been a major center of diversification for them, as the majority of fossils of this group are known from there. Following this, they saw an explosion in diversity during the Cenomanian, possibly due to the high sea levels of the Tethys at the time and the resulting impact on geography and food distribution, with the group evolving numerous different body plans. However, they were devastated by the Cretaceous–Paleogene extinction event and saw a drastic reduction in range. Only a few freshwater species in the genera Diplomystus and Guiclupea survived primarily in North America and China (although the unusual Gasteroclupea of South America appears to have briefly survived into the Paleocene), including Diplomystus dentatus of the famous Green River Formation. A few marine lineages survived in the Tethys Ocean near modern Italy, such as "Diplomystus" trebicianensis in the Paleocene and Eoellimmichthys, the last marine ellimmichthyiform, during the Eocene. The last surviving ellimmichthyiform, Guiclupea superstes, was a freshwater species that occurred in southern China during the Oligocene, representing the youngest member of the group.
Taxonomy
Based on Marramà & Carnevale (2026), in taxonomic order, with additions where relevant:
Genus †Codoichthys Silva Santos, 1994 Genus †Horseshoeichthys Newbrey, Murray, Brinkman, Wilson & Neuman, 2010 Family †Ancashichthyidae Ordóñez, Arratia, Tejada & Chacaltana, 2026 Genus †Aijaichthys Ordóñez, Arratia, Tejada & Chacaltana, 2026 Genus †Ancashichthys Ordóñez, Arratia, Tejada & Chacaltana, 2026 Family †Sorbinichthyidae Bannikov & Bacchia, 2000 Genus †Sorbinichthys Bannikov & Bacchia, 2000 Family †Scutatuspinosidae Silva Santos & Silva Corréa, 1985 Genus †Foreyclupea Vernygora, Murray & Wilson, 2016 Genus †Scutatuspinosus Silva Santos & Correa, 1985 Genus †Ranulfoichthys Alvarado-Ortega, 2014 Genus †Ornategulum Forey, 1973 Family †Gasteroclupeidae Signeux, 1964 Genus †Diplomystus Cope, 1877 Genus †Guiclupea Chen, Chang, Wu & Liao, 2018 Genus †Gasteroclupea Signeux, 1964 Family †Armigatidae Murray & Wilson, 2013 Genus †Armigatus Grande, 1982 Genus ?†Pugliaclupea Taverne, 2004 Family †Paraclupeidae Chang & Chou, 1977 Genus †Caboellimma de Figueiredo & Gallo, 2023 Genus ?†Kwangoclupea Taverne, 1997 Subfamily †Thorectichthyinae Murray & Wilson, 2013 Genus †Thorectichthys Murray & Wilson, 2013 Subfamily †Eoellimmichthyinae Marramà & Carnevale, 2026 Genus †Eoellimmichthys Marramà, Bannikov, Kriwet & Carnevale, 2018 Genus †Ezkutuberezi Poyato-Ariza, Lopez-Horgue & García-Garmilla, 2000 Subfamily †Triplomystinae Murray & Wilson, 2013 Genus †Triplomystus Forey, Yi, Patterson & Davies, 2003 Genus †Scutatoclupea Bannikov, 2015 Genus †Paraclupeinae Chang & Chou, 1977 Genus †Ellimma Jordan, 1913 Genus †Ellimmichthys Jordan, 1919 Genus †Paraclupea Sun, 1956 Genus †Rhombichthys Khalloufi, Zaragüeta-Bagils & Lelièvre, 2010 Genus †Tunisiaclupea Boukhalfa, Wu, Ben Ali & Fang, 2019 Genus †Tycheroichthys Hay, Cumbaa, Murray & Plint, 2007
Prior to the 2026 revision, Ellimmichthyiformes was treated as comprising 3 suborders (Armigatoidei with Armigatidae, Sorbinichthyioidei with Sorbinichthyidae & Gasteroclupeidae, and Ellimmichthyoidei with Paraclupeidae), a division now known to be paraphyletic.
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