Boreomysinae is a subfamily of large, mostly deep-water oceanic mysid crustaceans from the family Mysidae. The name, which can be translated as "northern mysids", comes from the genus Boreomysis G.O. Sars, 1869, established for Boreomysis arctica (Krøyer, 1861) from the boreal waters of Atlantic. As more species have been discovered subsequently, the subfamily is considered panoceanic, and includes 38 species from two genera, Boreomysis and Neobirsteiniamysis Hendrickx et Tchindonova, 2020.

Boreomysinae is a primitive group, uniquely distinguished from other subfamilies of Mysidae by the presence of the seven pairs of oostegites, which can be maximum four in other subfamilies, and by the incomplete proximal suture on the uropodal exopods (either complete and distal or completely absent in the rest of subfamilies).

Boreomysinaes show wide diversity in the structure of eyes, from rather reduced to large with well-developed cornea.

Being an ancient group of crustaceans, possibly originated in the beginning of Mesozoic era, boreomysines are considered living fossils.

...