CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Caught in fraganti: actual and Holocene, crowded Rosselia-like mud-lined tubes produced by spionid polychaetes
Autor/es:
E.B. OLIVERO; LOPEZ CABRERA, M.I; ERCOLANO B.; PITTALUGA S.; LIZARRALDE Z
Lugar:
Roca, Rio Negro
Reunión:
Otro; Reunion de comunicaciones de la Asociacion Paleontologica Argentina; 2012
Institución organizadora:
APA-IIPG Universidad de Rio Negro
Resumen:
Based on studies in Japan, M. Nara has proposed terebellid polychaetes as the probable trace maker of Rosselia socialis Dahmer. Our study on actual mud-lined tubes of Scolecolepides uncinatus Blake (Polychaeta, Spionidae) from the Rio Gallegos estuary (Santa Cruz Province, Argentina) and similar biogenic structures found in raised Holocene deposits provides evidence that Rosselia can be produced by spionid polychaetes as well. The tube-dwelling S. uncinatus occurs in crowded populations of 250 to 1500 individuals per square meter. The tubes, built in organic-rich, black or dark-gray silty-clay are mostly vertical and straight and rarely oblique, with curved segments, or forming wide U-tubes. The tubes, up to 20-25 cm long, have a central cylindrical lumen (4-5 mm wide) coated with mucus,  which is surrounded by pale brown to orange, spindle-shaped muddy laminae produced by the polychaete by successive splitting of cylindrical laminae inside the lumen. The sediment laminae of the host muds are commonly deformed around the tube. The same biogenic structure is also present in upper intertidal, raised Holocene deposits exposed south of the Río Gallegos estuary. Here, crowded Rosselia are preserved in mudstones as concentrically laminated rings surrounding a central lumen or as vertical, spindle-shaped chimneys, elevated over the surface. A polished section of a resin-impregnate specimen reveals the diagnostic, internal spindle shape lamination surrounding the central lumen typical of the trace fossil Rosselia