ASTERIACITES LUMBRICALIS

About 30 star-shaped traces have been analysed, and all specimens resemble the typical morphology of Asteriacites lumbricalis (Figure 4). Quality of preservation is highly variable. Most traces are represented by poorly preserved convex hyporeliefs. It is, however, always possible to identify 4-5 rays tapering toward the tip. Rays originate from a central structure (average diameter 4 mm) that in the majority of the specimens is undifferentiated. The most informative traces show morphological details such as delicate transversal or V-shaped striations on the rays. Those are produced by the regular digging action of the tube feet, moving sediment outward from beneath the arms (Seilacher 1953). Locally, a shallow impression is visible in the central area. The few traces preserved as concave epireliefs did not provide any further detail. Trace diameters (arm tip to arm tip) range from 5 to 21 mm with more than half having a diameter of less then 13 mm. The arms are moderately long in relation to the central structure with lengths ranging from 3 to 18 mm. Arm thickness ranges from 1 to 5 mm.