Peculiar and Novel Morphologies in Paleozoic Brittle Stars (Echinodermata, Ophiuroidea) from the Lower Devonian Hunsrück Slate of Germany
The cheiropterasterids Cheiropteraster giganteus and two species of Loriolaster exhibit an atypical skin membrane that covers the entire interradius between arm tips. Recognized here are unusual dorsal extensions of the lateral ossicles that appear to act as membrane supports near the disk margin in both taxa. Cheiropteraster giganteus also has peculiar ambulacrals that exhibit broad, pore-like openings that extend from the ventral to the dorsal surface. The laterals of Loriolaster are laterally elongated and ventrally flattened instead of providing support to and protection of the podial basins. The rare, multi-armed furcasterid Kentrospondylus decadactylus bears novel, V-shaped, prong-like articulations on its ambulacrals, features that are lacking in the otherwise very similar Eospondylus primigenius. New among known furcasterid morphologies, Lapworthura lehmanni has arms covered dorsally by spine-bearing scales. The ophiurinid Ophiurina lymani bears small diamond-shaped dorsal arm ossicles but lacks their ventral counterparts.
Soft-tissue preservation is recognized in at least four species of Hunsrück ophiuroids. Previously, pyrite textures of the disk membrane of Loriolaster were shown to be consistent with soft-tissue preservation. However, the latter form of morphological preservation must be carefully separated from artificial pyrite structures that are presented here.