A GIANT EGG AND THE OLDEST AVIAN VOCAL ORGAN: INSIGHTS INTO VERTEBRATE SOFT TISSUE PRESERVATION FROM CRETACEOUS OF THE JAMES ROSS BASIN, ANTARCTIC PENINSULA

For more than 100 years, fossil remains from the islands comprising the James Ross Archipelago have offered exceptional insight into diversity and extinction in the high southern latitudes. However, only recently have unique vertebrate soft-tissues been discovered. These findings lend new insight into the taphonomy of these sites. A concretionary facies of the marine Maastrichtian Sandwich Bluff Member of the Lopez de Bertodano Formation on Vega Island preserves, three-dimensionally, the delicate elements that support the airway and vocal folds of an avian syrinx, or vocal organ. The elements are preserved close to life position with a skeleton in a concretion from this unit. A giant soft-shelled egg that was originally primarily proteinaceous is preserved in a distinct unit, a comparatively fine-grained, grey sandy siltstone horizon of the marine Maastrichtian Lopez de Bertodano units of Seymour Island. Available data suggest a comparatively shallow burial history and ephemeral Oxygen available in a dominantly anoxic environment. The small number of other described soft-shelled eggs and mineralized airway cartilages recovered globally from the Mesozoic and Cenozoic are nearly all known from terrestrial lacustrine or fluvial deposits. Here, I present details concerning the taphonomy and hypothesized circumstances for exceptional preservation in these remains. Comparisons are made with the preservational record of related vertebrate tissues in the fossil record globally. These data may inform the discovery of other similar vertebrate soft tissues.