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GEOREF RECORD

Repeated regeneration of crinoid spines in the Upper Pennsylvanian of eastern Ohio; evidence of elevated predation intensity and significance for predator-driven evolution of crinoid morphology

James R. Thomka and Donald B. Eddy
Repeated regeneration of crinoid spines in the Upper Pennsylvanian of eastern Ohio; evidence of elevated predation intensity and significance for predator-driven evolution of crinoid morphology
Palaios (November 2018) 33 (11): 508-513

Abstract

Regeneration of portions of the crinoid endoskeleton following loss to predation attempts or autotomy is a well-known phenomenon. To date, however, most effort has focused on patterns, frequencies, and evidence of regeneration of arms and portions of the calyx, with few reports of unusual or significant regeneration-related features preserved in isolated ossicles. Here we describe brachial spines belonging to undetermined pirasocrinid (cladid) crinoids from the Upper Pennsylvanian Ames Member of the Glenshaw Formation of east-central Ohio that display evidence for multiple episodes of breakage and regeneration. As evidenced by major size discontinuities along the length of single spines, some specimens regenerated at least two times during the lifespan of the individual; such a pattern of repeated regeneration of a single skeletal element has not previously been documented. Given the position of these spines on the elevated crown of a moderately long-stemmed crinoid, frequent snipping by predatory fishes seems the most likely interpretation for the observed pattern. The repeatedly regenerated specimens occur in an assemblage displaying an unusually high regeneration frequency among pirasocrinid brachial spines, with over 30% of spines displaying at least one plane of regeneration. Paradoxically, pirasocrinids are unfavorable as prey items relative to other organisms and co-occurring crinoids; hence, it is most likely that associated biota (e.g., commensals, parasites) were the true targets of predators. This assemblage supports the interpretation that the development of extreme spinosity in pirasocrinids was largely driven by predation. However, this morphological pattern may largely represent an evolutionary strategy rooted in minimizing collateral damage incurred by predation on other organisms rather than direct predation on the crinoids themselves.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 33
Serial Issue: 11
Title: Repeated regeneration of crinoid spines in the Upper Pennsylvanian of eastern Ohio; evidence of elevated predation intensity and significance for predator-driven evolution of crinoid morphology
Affiliation: University of Akron, Department of Geosciences, Akron, OH, United States
Pages: 508-513
Published: 201811
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 39
Accession Number: 2019-002294
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N40°02'60" - N40°02'60", W81°19'60" - W81°19'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 2019
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