A new trace fossil from the Cambrian Bright Angel Shale, Grand Canyon, Arizona ( USA).

Angulichnus alternipes n. ichnogen. and n. ichnosp. is a distinctive ephichnial trail from the Middle Cambrian Bright Angel Shale at Horn Creek, Grand Canyon, Arizona. It consists of a cental zig-zag furrow bordered by biserially opposed alternating tracks. The trail cannot be attributed to a trilobite and is therefore important as an indicator of the presence of nontrilobite arthropods in the Bright Angel Shale. An arthropod similar to Habelia optata from the Burgess Shale would be a convincing trail-former. Sedimentologic analysis indicates that the heterolithic facies represents storm-induced deposition of sand, followed by a low-energy period during which traces were formed as mud settled to the bottom.-from Authors