9706071 Baumiller Crinoids were an important component of ancient marine environments and an excellent record of their diverse morphologies has been preserved, as is demonstrated by over 900 described genera. Yet 'm spite of their importance and diversity, our interpretations of their evolutionary history and paleoecology are limited and many questions remain unanswered. Two problems will be tackled in this study: I)are the predictions implicit 'm the tiering model (Ausich, 1980) supported by the pattern of spatial distribution of individuals of the same species? And 2) what structural or functional rules govern the growth of stalked crinoids? To tackle the first problem, one prediction implicit in the tiering model (Ausich, 1980), namely that the same-tier, upstream neighbors of crinoids interfere with feeding and that interferences should be avoided, will be tested by quantifying the patterns of spatial distribution of a living isocrinid, Neocrinus decorus. The patterns will be quantified by digitizing photos taken from a submersible.A first-order prediction states that if resources are limiting, since individuals of the same species utilize the same resources upstream neighbors should be avoided or should lie beyond some critical distance. Manipulations of in situ specimens and specimens 'm a flow tank will be used to further assess whether crinoids actively avoid interference. Another test of this hypothesis will involve collecting several 'individuals of N. decorus by submersible, tagging and redeploying them onto a small area, and episodically monitoring their pattern of distribution; a non-random pattern would support the hypothesis. A paleontological prediction of the intraspecific avoidance hypothesis is that the spatial patterns of distribution characterizing avoidance should be expressed only among taxa capable of relocation (e.g.: advanced cladids, articulates), but not among those taxa permanently attached to the substrate. Tests of this prediction will involve obt aining data on the spatial distribution of complete individuals of the same species from a single bedding plane of a burial horizon (e.g.: LeGrand, Burlington, Crawfordsville) and determining whether the pattern differs from random and is consistent with the hypothesis of avoidance. Results of all these approaches will provide a basis for assessing the relative importance of factors such as hydrodynamic regime and nutrient limitations to crinoid autecology and, possibly, evolutionary history. To determine if structural or functional rules govern crinoid morphology , stalk length and diameter and arm length will be measured for fossil taxa and for extant crinolds collected by submersible. Comparison of these data to predictions based on three scaling models, geometric, stress, and elastic, will be used to determine if the observed data support any of the models. Stalked crinoid-. which are rheophiles utilize a feeding posture which requires a certain flexure of the stalk, and these crinolds are predicted to scale according to the model of elastic similarity. If that prediction is home out for such crinoids, i.e., those with "standard" ecologies (rheophiles utilizing a Parabolic Filtration Fan Posture), fossil taxa thought to have had unusual ecologies (calceocrinids, Seirocrinus, Pentacrinus) will be examined to determine if they scaled according to rules different from elastic similarity. A successful completion of the project will solve some major problems of crinoid functional morphology and test an important ecological and paleoecological model, that of tiering. Although crinoids are the focus here, the methods developed have broader implications. For example, the principles governing crinoid morphology should also govern the growth of other aquatic rheophiles.
