101-9 Infestation of the Early Devonian crinoid meadow on the shelf of northern Gondwana

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns

Presenting Author:

Michal Zaton

Authors:

Zaton, Michal¹, Przemyslaw, Gorzelak², Berkowski, Blazej³, Zapalski, Mikolaj K.⁴, Jakubowicz, Michal⁵, Salamon, Mariusz A.⁶, Kershaw, Stephen⁷, Krol, Jan J.⁸, Majchrzyk, Aleksander⁹

Abstract:

Since early Palaeozoic time, stalked crinoids provided a unique substrate for attachment of various epi- and endobiontic organisms, which gained an access to suspended food particles and avoided competition with benthic filter-feeding organisms living on the sea bottom below. As many colonizers were partly or completely embedded by the crinoid stereom, the syn vivo (during the host’s life) biotic interactions have a chance to be uniquely preserved in the fossil record. Here, we studied a rich collection of the Lower Devonian (Pragian) crinoid stem fragments (pluricolumnals) from the famous locality at Hamar Laghdad in Morocco. The results obtained show that more than 50% of pluricolumnals bear signs of syn vivo colonization. The crinoids were predominantly infested by Tremichnus pits-producing epibionts (found in 43% of pluricolumnals) and organisms leaving different bioclaustrations and galls/swellings on the crinoid stems. Additionally, many crinoids were also syn vivo colonized by other epibiontic crinoids, tabulate and rugose corals. Comparing to other known crinoid-epibiont symbiotic associations from elsewhere, that from Hamar Laghdad seems to be the most severly infested by parasitic Tremichnus-producing epibionts. Taking the results obtained, together with previous data from south-western Morocco (Tala n’Taleb), into account, it seems that Early Devonian crinoid biocoenoses of the southern Rheic Ocean realm witnessed severe infestations of ectoparasitic epibionts which easily infected the hosts forming dense populations on the sea floor.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8001

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