Zoological Journal of the Linnean Society
J.*, Ivantsov, A.Y. & Deulin, Y.V.
A mass occurrence of schooling,
weakly sclerotized eocaridid shrimps in the Early Devonian pelagic
environment of northern Russia suggests that the body-plan of the
Eumalacostraca originated as an adaptation to swimming in the open sea.
They probably replaced their ecological analogues, the archaeostracan
phyllocarids Caryocaris, as a consequence of the rebuilding of the global marine
environment during the later Ordovician. This may explain the rarity of
the eumalacostracans in the Devonian and the difficulty with documenting
their links with the archaeostracans. The new eocaridid shows
similarities to the Carboniferous Anthracophausia
in the general appearance and weak sclerotization of the carapace and
appendages, but lacks its derived characters. The morphology of the
pleural lobes, which have minute spines, is the only identified
distinguishing character of the proposed new genus and species Archangeliphausia
spinosa gen. et sp. nov. Its carapace was probably firmly connected
dorsally with the thoracic segments. The only associated fossils of the
assemblage represent a bizarre archaeostracan Pechoracaris aculicauda gen. et sp. nov., with a weakly sclerotized
carapace lacking any hinge or rostral plates but with reduced furca, an
extremely long caudal spine and pleopods transformed into spines.