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CRINOID ANCHORING STRATEGIES FOR SOFT-BOTTOM DWELLING (SEILACHER AND MACCLINTOCK, 2005)

¹ Department of Palaeontology, Nationaal Natuurhistorisch Museum, Postbus 9517, NL-2300 RA Leiden, The Netherlands donovan@naturalis.nnm.nl

The first 300 words of the full text of this article appear below.

Seilacher and MacClintock (2005) have presented scenarios for the functional morphology of the attachment structures of a number of Paleozoic crinoid taxa. Their interpretations include many with which echinoderm workers will agree, but there also are some that will raise eyebrows. The concept of the ecology of extant stalked crinoids was revised completely when Macurda and Meyer (1974) demonstrated that they are rheophiles, not rheophobes as previously envisaged. It is now recognized that isocrinines can relocate by crawling with their arms (Messing et al., 1988), can regenerate the crown following autotomy (Amemiya and Oji, 1992), have mutable collagenous tissues in the column (Wilkie et al., 1993), and have contractile connective tissue in the arms, cirri, and, perhaps, the column (Birenheide and Motokawa 1996). In short, the past 30 or so years have seen the functional interpretation of crinoids change from passive rheophobes to active rheophiles, based on both direct observation by research submersible and laboratory analysis and examination. Yet, most of these observations are not generally applicable to the fossil record, even by inference, because the isocrinines (and closely related stalkless comatulids) have adaptations of the skeleton and soft tissues not found in other crinoid groups, particularly those of the Paleozoic. Some of the non-isocrinine groups considered by Seilacher and MacClintock (2005) suffer from inappropriate comparisons, interpretations, or both. The following brief comments relate to some of the more questionable points of their analysis.

	CONSTRUCTIONAL SETTING

 
Seilacher and MacClintock (2005, p. 225) are correct, I'm sure, in saying that "... the ability of mutable collagen to switch between a stiff and an elastic stage allows for controlled flexibility [of columns and cirri] ...," but I disagree most strongly when they continue "... or even some kind of active motion (Donovan, 1989, . . . [Full Text of this Article]

	ANCHORING STRATEGIES

 

	EXAMPLES OF CRINOIDS ROOTS

 
Myelodactylids
Ancyrocrinus
Eucalyptocrinites
Edriocrinus