EARLIEST-KNOWN UNIRAMOUS ARTHROPOD

THE earliest-known fully terrestrial animals are myriapods from the Upper Silurian of Britain1, and unnamed myriapod-like fossils have recently been reported from Lower Silurian marine deposits in Wisconsin2,3. Myriapod-like burrows in Upper Ordovician soils from Pennsylvania4 indicate the existence of earlier land animals. Here I report the discovery of a myriapod-like fossil from marine deposits in the Middle Cambrian Wheeler Formation of Utah that extends the record of myriapod-like body fossils back by approxiá-mately 100 Myr. It thus represents the earliest-known uniramous arthropod, and may have special significance with respect to the ancestry of the terrestrial myriapods (centipedes and millipedes) and insects. © 1990 Nature Publishing Group.