Ellimmichthyiformes is an extinct order of prehistoric bony fish that lived during the Lower Cretaceous to the Oligocene. It is related to the order Clupeiformes. They are also known as double-armored herrings.

This lineage was ultimately demolished by the Cretaceous–Paleogene extinction event. The last genus, Guiclupea, was a freshwater fish. It was also the youngest of them all.

The ellimmichthyiforms were small and most genera did not exceed 10 cm. One of the most famous and well-known genera was Diplomystus. Some of the representatives had strange shapes. For example, Rhombichthys had a deep body.

• Suborder †Armigatoidei
  • Family †Armigatidae
    • Genus †Armigatus
    • Genus †Diplomystus
    • Genus †Guiclupea
    • Genus †Horseshoeichthys
• Suborder †Ellimmichthyoidei
  • Family †Paraclupeidae
    • Genus †Caboellimma
    • Genus †Codoichthys
    • Genus †Ellimma
    • Genus †Ellimmichthys
    • Genus †Eoellimmichthys
    • Genus †Foreyclupea
    • Genus †Ezkutuberezi
    • Genus †Kwangoclupea
    • Genus †Paraclupea
    • Genus †Ranulfoichthys
    • Genus †Rhombichthys
    • Genus †Scutatoclupea
    • Genus †Scutatuspinosus
    • Genus †Thorectichthys
    • Genus †Tunisiaclupea
    • Genus †Tycheroichthys
• Suborder †Sorbinichthyoidei
  • Family †Sorbinichthyidae
    • Genus †Sorbinichthys
  • Family †Gasteroclupeidae
    • Genus †Gasteroclupea

Diplomystus is possibly the most famous genus of the Ellimmichthyiformes. It was a freshwater fish. It had seven species.

Rhombichthys was a bizarre-looking fish. It had a very deep body because of its high dorsal fin.

Armigatus lived during the Cretaceous. It means "bearer of armor". It did not exceed 10 cm in length.

Gasteroclupea resembled a fish of the genus Pristigaster. This was mainly due to convergent evolution, so it is not related to Pristigaster.

• Australosomus
• Scombriformes
• Acanthopleurus
• Helicoprion
• Cretalamna
• Onchopristis
• Sclerorhynchoidei
• Pachycormiformes

1. Márcia Aparecida dos Reis Polck, Valéria Gallo, Francisco J. de Figuieredo, Samuel Magalhães Viana, Viviane Sampaio Santiago dos Santos, João Villar de Queiroz Neto, Ricardo Jorge Jahnert (March 2020). "†Ellimma longipectoralis sp. nov. (Teleostei: Clupeomorpha: †Ellimmichthyiformes) from the Aptian of the Santos Basin, southeastern Brazil". ScienceDirect.