Archaeoniscus

Archaeoniscus Temporal range: Bajocian–Albian PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of A. brodiei
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Superorder:	Peracarida
Order:	Isopoda
Suborder:	Sphaeromatidea (?)
Family:	†Archaeoniscidae Haack, 1918
Genus:	†Archaeoniscus Milne-Edwards, 1843
Type species
†Archaeoniscus brodiei Milne-Edwards, 1843
Species[1]
†A. brodiei Milne-Edwards, 1843 †A. edwardsii Westwood, 1854 †A.? texanus Wieder and Feldmann, 1992 †A. aranguthyorum Feldmann et al., 1998 †A. coreaensis Park et al., 2012 †A. italiensis Jones et al., 2014

Archaeoniscus (/ˌɑːrkiːˈoʊnɪskəs/) is a genus of prehistoric isopods that first appeared during the Bajocian stage of the Middle Jurassic. It is a widespread genus with a paleogeographic distribution encompassing the continental margin environments of the central Atlantic Ocean and the western Tethys Ocean. Fossils of Archaeoniscus suggest that this genus lived in diverse aquatic habitats, including the marine, paralic, and freshwater environments. While earlier descriptions suggested that it may have had an ectoparasitic association with fishes, some researchers argue that at least two species, A. aranguthyorum and A. coreaensis, lived a benthic free-living lifestyle based on morphological characteristics that are either unsuitable for or unrelated to parasitic behavior.

Six species have been named: two species are known from the Jurassic period rocks in Europe, and the other four are known from the Cretaceous period rocks in Europe, North America and East Asia. Of these species, the taxonomic position of the only Late Cretaceous species, A. texanus, is uncertain, for some researchers claim that this species should be neglected because of the significant morphological differences in comparison to the other species within the genus. Some specimens of the most completely known species, A. aranguthyorum, suggest that the female individuals of this species possibly had brood pouches, indicating that the genus may have had sexual dimorphism. An alternative interpretation suggests that the brood pouches may actually be the impressions of the hindgut and anus. Additionally, two unnamed indeterminate species are known from the Early Cretaceous rocks in Mexico and Egypt.