REMARKABLE PRESERVATION OF FOSSIL WORMS (ANNELIDA: POLYCHAETA) FROM THE LA MESETA FORMATION (EOCENE), SEYMOUR ISLAND, ANTARCTICA

Fossils attributed to polychaete annelids typically consist of vertical or U-shaped tubes with little or no expression of the morphology of the cuticular surface of the worm. Open tubes collected in late early Eocene (Askin, 1993) rocks on Seymour Island, Antarctica (64°S, 56°W) preserve fine detail of the cuticular surface of a worm-like organism, tentatively assigned to the Polychaeta. The fossils occur in iron-rich concretions either as a hardground surface on the uppermost beds of the Valle de las Focas Allomember or in a transgressive sand sheet in the lowermost Acantilados Allomember(Marenssi, et al., 1998), or TELM1 (Sadler, 1988), of the La Meseta Formation. The tubes are approximately 1 cm in diameter and are up to 10 cm in length. The inner surface of the tube is lined by a layer of iron oxide less than 0.1 mm thick. Impressed into this lining is a transverse, chevron-like pattern of striations arrayed in bundles resembling the bandages on a mummy. These striated bundles are paired, with one part tapering in a posteroventral direction and the other part tapering in an anterodorsal direction. Together, they appear to comprise one metamere. Pits along the long axis of the tubes may represent openings for the extension of parapodia. This fine structure appears to be unique and represents among the best known replications of the surface morphology of a fossil annelid. These worms were probably vagile epifaunal - shallow infaunal bioturbators of the seafloor. This work was supported by NSF grant OPP 9909184 to Feldmann and Karen Bice. Logistic support was provided by the Instituto Antartico Argentino.