Primicaris is genus of Cambrian arthropod from the Chengjiang biota of China and the Burgess Shale of Canada. It contains a single described species, P. larvaformis.
Description
Specimens range from 2.08 to 6.04 millimetres (3⁄32 to 1⁄4 in) in length, and 1.50 and 4.20 millimetres (1⁄16 and 5⁄32 in) in maximum width. The undivided subovate-shaped dorsal shield covered the entire body, and wrapped around the front edge of the carapace, forming a doublure structure. The midline of the carapace exhibited thickening. There is a pair of slender uniramous segmented antennae, as well as ten pairs of biramous limbs. The exopods of these limbs are flagellate and bear setae, with the exopods decreasing in size posteriorly. The endopods are poorly preserved.[1]
Taxonomy
Its specimens were once thought to be meraspids of Naraoia spinosa.[1] Although their phylogenetic position has been described as "problematic",[2] recent studies have suggested them to be marrellomorphs belonging to the subgroup Acercostraca.[3][4]
