Thomka et al., 2022

Author(s):Thomka, J. R., Vinn, O., Toom, U.
Year:2022
Title:Site-selectivity of symbiotic (parasitic?) pits in crinoid column material from the middle Silurian (Wenlock: Sheinwoodian) of western Estonia
Journal:Ichnos
Volume:29
Number:2
Pages:71-75
Abstract

Crinoid specimens containing symbiotic (potentially parasitic) pits are relatively rare in Silurian strata of Estonia. The first specimen of middle Silurian-age (Wenlock: Sheinwoodian) crinoid material containing such pits—a pluricolumnal of uncertain affinity—was recently reported from the Jaagarahu Formation of Saaremaa Island. The presence and morphology of pits were previously described, but a noteworthy paleoecological phenomenon that was not initially documented involves the site-specificity of pit occurrence along the pluricolumnal. All 21 of the pits distributed around the lateral circumference of the specimen are located on plate sutures, demonstrating a degree of site-selectivity that contrasts strongly with the more random distribution of pits observed in most Silurian crinoid assemblages. The underlying paleoecological driver of this site-selectivity remains enigmatic, particularly considering some reports that suggest a preference for the latera rather than the sutures of Paleozoic crinoid columns.

Keywords:Bioerosion, Echinodermata, Estonia, Paleontology, Silurian, Trace fossils
DOI:https://doi.org/10.1080/10420940.2022.2047038
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