Palaeobiology, taphonomy and stratigraphic significance of the trilobite BUENELLUS from the Sirius Passet Biota, Cambrian of North Greenland

The Sirius Passet Biota, collected from the lower Buen Formation (Cambrian Series 2, Stage 3), North Greenland, contains one species of trilobite, the nevadiid Buenellus higginsi Blaker, 1988. The species shows considerable morphological variation, especially in exoskeletal width. Many specimens of B. higginsi show some form of exceptionally preserved, non-biomineralised tissue. Structures interpreted as alimentary tracts and probable digestive glands are commonly preserved by silica and limonite. Antennae are rarely preserved, apparently through replication in clay minerals. Tendinous bars in the axial region also seem to be preserved by replication in clay minerals. Mineral-filled gut tracts in B. higginsi suggest they were fluid-filled at the time of burial, and that the species was a non-durophagous predator. Healed injuries, some of which are the result of unsuccessful predaceous attacks, are uncommon in B. higginsi. Other exoskeletons show evidence of post-mortem disruption, perhaps scavenging. Buenellus higginsi, one of the earliest known trilobites from Laurentia, seems to have played an important role in the Sirius Passet ecosystem, serving both as predator on, and prey for, contemporary animals.