Geologica Belgica

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Rugosans immured in Silurian Paleofavosites; Brassfield Formation (Llandovery) of Ohio

(volume 15 (2012) — number 4 - Proceedings of the XIth International Symposium on Fossil Cnidaria and Porifera)
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Mots-clés : Streptelasma, bioclaustration, aggression hierarchy, Cnidaria, epibiont.


The occurrence of a solitary rugose coral, Streptelasma sp., anchored within colonial skeleton of the tabulate coral Paleofavosites prolificus is here reported. Numerous specimens of Streptelasma were found within three coralla of this tabulate species among 55 collected from the uppermost 30 cm of the Lower Silurian (Llandovery) Brassfield Formation at Fairborn, Ohio. These rugosans are largely immured in the favositid coralla, and, as bioclaustrations, reveal important information on the paleobiology of both species. However, the immuring of some Streptelasma within Paleofavosites coralla was not complete during the life of the rugosan, as calice openings of these are present at the corallum surface. Complete immuration (or total overgrowth) indicates that the rugosan no longer competed successfully for space; whether entombment occurred after the death of the rugosan or was the cause of its death is unknown. Streptelasma, in assuming an epibiotic lifestyle probably benefited from the secure attachment to the larger, stable colonial form of Paleofavosites prolificus and were able to exist within this particular Brassfield facies interpreted to have been a vigorous, current-swept environment. These high energy environments would have been inimical to the small, light-weight rugosans living as isolated corallites. The successful settling and growth of the rugosans on the tabulate colonies reflects their higher status in an aggression hierarchy. This interspecies interaction indicates an early Paleozoic development of an aggression hierarchy of corals belonging to the Rugosa and Tabulata (Phylum Cnidaria).

To cite this article

James E. SORAUF & Don L. KISSLING, «Rugosans immured in Silurian Paleofavosites; Brassfield Formation (Llandovery) of Ohio», Geologica Belgica [En ligne], volume 15 (2012), number 4 - Proceedings of the XIth International Symposium on Fossil Cnidaria and Porifera, 220-225 URL :

About: James E. SORAUF

25 Susanna Drive, Durham, North Carolina, 27705, USA;

About: Don L. KISSLING

406 Welch Avenue, Berthoud, Colorado 80513, USA;