The first Silurian trilobite with three-dimensionally preserved soft parts reveals novel appendage morphology

<p>The first Silurian trilobite known with soft parts preserved, a <i>Dalmanites</i> species, is described from the Herefordshire Lagerstätte. Biramous appendages and much of the alimentary system are evident.  High-fidelity three-dimensional preservation reveals a novel, double arrangement of the exopod filaments, interconnected by a presumed membranous sheet. This morphology explains a misinterpretation of the exopod as supporting spiral structures, originally reported nearly 150 years ago. The new exopod morphology is considered primarily respiratory in function and comparison with other trilobite limbs suggests that it may be unique to Phacopida.</p>