PYRITIZED TUBE FEET IN AN OPHIUROID (ECHINODERMATA) FROM THE HUNSRUECK SLATE (EMSIAN, LOWER DEVONIAN) OF GERMANY

The Lower Devonian Hunsrueck Slate of Germany is known for its great fossil diversity of over 260 species. Preservation of both delicate skeletal elements and non-mineralized tissues make the Hunsrueck Slate comparable in its comprehensiveness and potential to other fossil conservation deposits. Pyritization, deformation, and partial dissolution render study of Hunsrueck fossils difficult. Traditional mechanical preparation methods damage fossils therefore radiographic techniques were long employed, but these methods tend to yield controversial images.

Otto (1994, 2000) argued that all reports of volatile non-mineralized tissues from the Hunsrueck are misidentification of skeletal structures because identifications were usually based on interpretations of poor x-ray images.

In contrast, we report here the first occurrence of pyritized tube feet in the Hunsrueck protasterid ophiuroid, Bundenbachia beneckei Stuertz. The specimen was prepared using a special airbrasive powder and technique developed by German amateur fossil collectors especially for Hunsrueck Slate fossils. This technique allows preparation of extremely delicate pyritized structures without damage. The fully prepared specimen of B. beneckei exposes two ventral arm surfaces. Long, thick tube feet extend from within each podial basin across the margins of the laterals. Tube feet are nearly twice as long and much thicker than the lateral spines. Their length and size suggest that B. beneckei was able to seize and manipulate larger items of food, possibly live prey. Their length is also consistent with size predictions based on the shape of protasterid ophiuroid trace fossils. The sizable tube feet in B. beneckei could have served as a primary means of locomotion as is more typical of asteroids. Most modern ophiuroids primarily use their flexible arms for locomotion and food manipulation.

Volatile non-mineralized structures are preserved in the Hunsrueck Slate. Improved preparation methods enable documentation of delicate materials and provide a new potential for the delineation of both skeletons and associated non-mineralized tissues in the Hunsrueck Slate.