While all modern crinoids are benthic filter feeders, some fossil species found in low-oxygen Konservat-Lagerstätten probably were pelagic. Pseudoplanktonic forms were mostly attached to driftwood (Seirocrinus, Traumatocrinus, Melocrinus); they had long, rope-like stems and enlarged, permanently splayed filter fans, as required for a passive tow-net function. However, the short and heavily cirrated stem of another driftwood-dweller (Pentacrinites) suggests active filter feeding. If the buoyant lobolith of Scyphocrinites acted as a swim bladder, this crinoid, by the same tow-net principle, could have made use of velocity gradients near a boundary layer. Paradigms are different for stemless forms, whether they floated passively over the bottom (Uintacrinus) or filtrated actively in the water column (Roveacrinids and Saccocoma). Some of the proposed models could not function with the muscular and ligamentary system of modern forms. Nevertheless, they represent distinctive peaks in the adaptive landscape that can be tested using taphonomic, morphological, and evolutionary evidence.
How to translate text using browser tools
1 February 2004
Constructional Morphology of Pelagic Crinoids
ADOLF SEILACHER,
ROLF B. HAUFF
ACCESS THE FULL ARTICLE
It is not available for individual sale.
This article is only available to subscribers.
It is not available for individual sale.
It is not available for individual sale.
PALAIOS
Vol. 19 • No. 1
February 2004
Vol. 19 • No. 1
February 2004