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Commensalism in the fossil record: Eunicid polychaete bioerosion on Pliocene solitary corals

100%

Martinell J., Domenech R.

Acta Palaeontologica Polonica

2009

tom 54

nr 1

143-154

Some solitary caryophylliid (Caryophyllia, Trochocyathus, and Ceratotrochus) and flabellid (Flabellum) scleractinian corals from Pliocene of Western Mediterranean exhibit long groove−shaped bioersional structures running along the surface of the thecae. They are epigenic structures produced by an episkeletozoan and therefore, they are described as Fixichnia. Here we propose Sulcichnus as a new ichnogenus, with three new ichnospecies (Sulcichnus maeandriformis, S. helicoidalis, and S. sigillum) to name this traces. Sulcichnus is attributed to the activity of polychaetes. Similar structures are recently produced by Lumbrineris flabellicola, a symbiotic eunicid which maintains a commensalistic relationship with solitary corals. In the fossil record, Sulcichnus occurs associated to shallow marine environments whereas their Recent counterparts are described on deep−marine corals. We interpret this as a consequence of a change in the environmental requirements of the coral/worm pair.

Bioerosion in shell beds from the Pliocene Roussillon Basin, France: Implications for the (macro)bioerosion ichnofacies model

80%

de Gibert J. M., Domenech R., Martinell J.

Acta Palaeontologica Polonica

2007

tom 52

nr 4

The marine Pliocene at the locality of Nefiach (Roussillon Basin, SE France) includes several shell beds constituted by oysters and scallops that bear a diverse and abundant bioerosion trace fossil assemblage. The most abundant trace fossils are Gnathichnus pentax and Radulichnus inopinatus, produced by the grazing activity of echinoids and polyplacophorans upon algae and other microorganisms coating shell surfaces. Other bioerosion traces include polychaete dwellings (Caulostrepsis taeniola and Maeandropolydora sulcans), sponge boring systems (Entobia isp.), and rare bryozoan borings (Pinaceocladichnus isp.), predation structures (Oichnus simplex and repaired durophagous scars), and foraminiferal fixation pits (Centrichnus cf. eccentricus). The trace fossil assemblage records short−term bioerosion in shellgrounds in a moderate energy setting as evinced by the dominance of epigenic or shallow endogenic structures produced in most cases by “instantaneous” behaviors. The assemblage can be assigned to the Gnathichnus ichnofacies, and it contrasts with that found in Pliocene rocky shores in the same geographic area, which are examples of the Entobia ichnofacies. The Gnathichnusichnofacies is validated as an archetypal one and its recurrency demonstrated since the Jurassic. Entobia and Gnathichnus ichnofacies have to be used in the Mesozoic and Cenozoic as substitutes of the previously existing Trypanites ichnofacies, which is still valid in the Palaeozoic.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Domenech R.

2 Martinell J.

1 de Gibert J. M.

1 2009

1 2007

Wyniki wyszukiwania

Commensalism in the fossil record: Eunicid polychaete bioerosion on Pliocene solitary corals

Bioerosion in shell beds from the Pliocene Roussillon Basin, France: Implications for the (macro)bioerosion ichnofacies model