A permanent, U-shaped dwelling burrow created by an animal that lived in the sediment but was a suspension feeder. The two parallel tubes are circular in section. Some organisms were capable of responding to rapid deposition or erosion. This response is reflected in the presence of concentric laminae on either side, either inside the two arms of the burrow or below the outer curve (or, in the form Diplocraterion yoyo, in both positions).
Subjects: Earth Sciences and Geography.