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The cover photograph is a longitudinal horizontal section through a small arthropod (sagittal length 4.5 mm) of as yet uncertain affinity. This arthropod is the most common element of a diverse "soft-bodied" fauna that has been recovered from concretions that occur in a volcaniclastic deposit in the Silurian (Wenlock) of Herefordshire, UK. All the taxa, including a variety of polychaetes, are preserved mainly in calcite and in three dimensions. The biota is only the third in the fossil record to yield three-dimensionally preserved polychaetes, thus confirming the truly exceptional preservation.

The specimen illustrated shows corresponding structures on the left and right hand lateral margins; from anterior to posterior these are sections through an arch-like cephalic shield and three thoracic tergites. The overlap between successive tergites increases posteriorly as this part of the specimen is flexed at 90 degrees to the plane of splitting. The most striking feature is the rosette-like arrangement of the bases of the stout, uniramous cephalic limbs at the posterior of the cephalic shield. These presumably surrounded a medial oral cavity. The distal parts of the cephalic limbs project both anteriorly and laterally. As the arthropod is preserved in three dimensions, the complex arrangement of the cephalic limbs within the cephalic shield can be reconstructed in precise detail. The basal parts of each appendage originate at or near the same horizontal level. However, the high number of large cephalic limbs was accommodated within the confines of the cephalic shield by having the distal parts of successive appendages "stacked" vertically above each other.

The taphonomy and palaeobiology of the biota is being studied by Professor Derek Briggs (Bristol), Dr. Patrick Orr (Oxford) Dr. Derek Siveter (Oxford) and Dr. David Siveter (Leicester). This research is being supported by the Natural Environmental Research Council (GR9/03132). Specimen, under water, photographed by Derek Siveter.

 

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Copyright: Coquina Press, July 1998
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