ABSTRACT
Oelandocaris oelandica Müller, 1983, was originally described from a single limbless fragment discovered in limestones from the Isle of Öland, Sweden. Subsequently, six, apparently conspecific specimens having preserved appendages were picked from the most productive Upper Cambrian ‘Orsten’ samples taken in Västergötland in southern Sweden. These new specimens permit a much more conclusive reconstruction and discussion of the systematic affinities of the species than was possible in 1983. The most significant feature of this approximately 1 mm long arthropod are its large antennulae (first pair of limbs), which are subdivided into three long, spine-bearing outgrowths (not rami). Most likely, all three anterior limbs were involved in food gathering, while the posterior limbs are, more or less, serially designed (large basipod with few median setae, endopod (four-or fivesegmented?), and a large, leaf-shaped exopod with strong marginal setae) and may have served mainly for locomotion (swimming). There are remarkable similarities to the coexisting, very abundant Upper Cambrian Agnostus pisiformis (Wahlenberg 1818), traditionally interpreted as a diminutive trilobite. O. oelandica also shares features with some of the derivatives of the stem lineage of the Eucrustacea/Labrophora, particularly Henningsmoenicaris scutula Walossek & Müller, 1990. These similarities are used herein to evaluate the feeding apparatus of the head region of these taxa. Our aim is to get a better picture of the development of the feeding apparatus in the early stem lineage of Crustacea and its significance as a useful data set for phylogenetic analyses. O. oelandica seems to represent the earliest offshoot of the stem lineage of Crustacea.
