New species of Kuqaia from the Lower Jurassic of Sweden indicates a possible water flea (Crustacea: Branchiopoda) affinity

Abstract

The enigmatic acid-resistant mesofossil genus Kuqaia is emended, a new species (Kuqaia scanicus) is instituted, and three established species are described from the Lower Jurassic (lower Pliensbachian) of the Kävlinge BH-928 core, in southern Sweden. Kuqaia has a distribution across the middle northern latitudes of Pangaea and is restricted to Lower to lower Middle Jurassic strata. Morphological characters support Kuqaia being the ephippia (resting egg/embryo cases) of Cladocera (Crustacea: Branchiopoda), and a probable early stem-group taxon of the Daphnia lineage. The paleoecology of the small planktonic crustaceans indicate purely fresh-water environments, such as lakes or ponds, all occurrences being in continental deposits, and the Kuqaia specimens possibly represent dry-season resting eggs. Chemical analyses of these and similar fossils, and of extant invertebrate eggs and egg cases are recommended to improve resolution of the biological affiliations of such mesofossil groups.