A Silurian ophiuroid with soft tissue preservation

Palaeozoic brittle stars are not equipped with the fused arm ossicles (vertebrae) that facilitate the remarkable mode of walking that characterizes living forms. Here we describe a stem ophiuroid from the Herefordshire Lagerstätte (Silurian, Wenlock Series) which is remarkable in preserving the body cavity uncompacted and long tube feet which lack suckers. We tentatively assign the specimen to Protaster. The morphology of the arms and attitude of the specimen suggest that locomotion was achieved by arm propulsion combined with podial walking. The ophiuroid was also capable of different types of feeding strategies. This protasterid ophiuroid increases the diversity of echinoderm higher taxa with preserved soft parts represented in the Herefordshire Lagerstätte.

Methods
Physical-optical tomography at 20-micron intervals; reconstruction as isosurface following virtual preparation in SPIERS (www.spiers-software.org).