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Journal of Paleontology

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THE APPLICATION OF FILTRATION THEORY TO FOOD GATHERING IN ORDOVICIAN CRINOIDS

¹ Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244-1070

Food gathering of some adult Upper Ordovician crinoids was modeled by means of filtration theory. The arm-branching patterns of the 13 species examined range from nonpinnulate isotomous arms to uniserial and biserial arms with numerous pinnules. Most taxa are roughly equivalent with respect to ambient current velocities and the nutrient contents needed from seawater. Two species with extensively branched arms have markedly higher nutritional requirements at any one ambient current velocity. The results are somewhat correlated with environment in the form of differential current velocities, water flow patterns, and food abundance and composition. The data are generally compatible with filtration theory and the environmental distributions of many Ordovician and other Paleozoic crinoids, and they reveal that Upper Ordovician crinoids had at least partially developed the ecological patterns seen in later Paleozoic crinoids. Various morphological, physiological, and behavioral changes can be employed by crinoids to alter their nutritional balance. The size distributions of food particles that are caught by the crinoids are modeled. These food particle distributions for the Ordovician fossils resemble those of modern crinoids. Relative to the population of food items, the distributions of particles that are trapped are shifted towards larger items because the crinoid filtration nets are more efficient at catching larger particles. Crinoids with relatively open filtration nets and large food-catching tube feet are generalized and feed on a wide range of food particles of a relatively large mean size. The more specialized taxa with extensively branched arms bearing small and closely packed food-catching tube feet are restricted to a more narrow range of smaller food particles.

This article has been cited by other articles:

				J. C. Brower Systematics and Paleoecology of Haptocrinus Buttsi, a New Species of Disparid Crinoid from the Upper Ordovician Hatter Limestone of Central Pennsylvania Journal of Paleontology, May 1, 2008; 82(3): 576 - 584. [Abstract] [Full Text] [PDF]

				J. C. BROWER SOME DISPARID CRINOIDS FROM THE UPPER ORDOVICIAN (SHERMANIAN) WALCOTT-RUST QUARRY OF NEW YORK Journal of Paleontology, January 1, 2008; 82(1): 57 - 77. [Abstract] [Full Text] [PDF]