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Molluskan Grazing Traces (Ichnogenus Radulichnus Voigt, 1977) on a Pleistocene Bivalve from Southern Brazil, With the Proposal of a New Ichnospecies

2018; Taylor & Francis; Volume: 26; Issue: 2 Linguagem: Inglês

10.1080/10420940.2018.1532898

ISSN

1563-5236

Autores

Renato Pereira Lopes, Jamil Corrêa Pereira,

Tópico(s)

Paleontology and Stratigraphy of Fossils

Resumo

The ichnogenus Radulichnus Voigt, 1977 Voigt, E. 1977. On grazing traces produced by the radula of fossil and recent gastropods and chitons. In Trace fossils 2, eds. T. P. Crimes, and J. C. Harper, 335–346. Geological Journal, Special Issue 9. [Google Scholar] is recorded for the first time from a bivalve, Anomalocardia brasiliana (Gmelin, 1791 Gmelin, J. F. 1791. Caroli a Linné, Systema Naturae. Tom. I, Pars VI. Leipzig: G.E. Beer, pp. 3021–3910. [Google Scholar]), in a late Pleistocene molluskan assemblage from the southern Brazilian coastal plain. Grazing traces comprise short (<1 mm), parallel furrows, arranged in rows on the inner (concave) shell surface and mostly concentrated in its central area. Radulichnus accommodates scratches on hard substrates produced by the radula of grazing gastropod or polyplacophorans. Our literature survey on fossil and extant traces, as well as studies on the grazing mechanism in living mollusks, document at least two distinct morphotypes that are related to differences in the feeding modes of the producers. We propose to distinguish a second ichnospecies of Radulichnus, in addition to the type, R. inopinatus Voigt, 1977 Voigt, E. 1977. On grazing traces produced by the radula of fossil and recent gastropods and chitons. In Trace fossils 2, eds. T. P. Crimes, and J. C. Harper, 335–346. Geological Journal, Special Issue 9. [Google Scholar] (produced by gastropods), which is named R. transversus isp. nov., and attributed to polyplacophorans. Grazing traces on the shell of A. brasiliana match the morphotype produced by polyplacophorans mollusks, and are indicative of its complex taphonomic history in comparison with other shells in this assemblage.

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