The oldest tongue worm: a stem-group pentastomid arthropod from the early middle Cambrian (Wuliuan Stage) of North Greenland (Laurentia)

Rare phosphatised fragments within small shelly fossil assemblages from the upper Henson Gletscher Formation (Cambrian, Miaolingian Series, Wuliuan Stage) of North Greenland (Laurentia) are described as Dietericambria hensoniensis n. gen. n. sp. Two pairs of minute cephalic limbs promote comparison with stem-group pentastomids, best known from the late Cambrian (Furongian) Orsten Lagerstätten of Sweden. The North Greenland occurrence is interpreted as the oldest yet described tongue worm and extends the record of pentastomids by about 15 m.y. Dietericambria hensoniensis preserves a unique median axial complex of uncertain function, probably an attachment organ; a mouth has not been identified. Isolated hooks and spicules in the samples from the Henson Gletscher Formation are compared to the grasping hooks and copulatory spicules of the extant pentastomid Raillietiella, although their interpretation is speculative.