BROMALITES FROM THE AMEGHINO (=NORDENSKJÖLD) FORMATION UPPER JURASSIC OF ANTARCTIC PENINSULA

Abstract

We present the study of the bromalites retrieved from the Upper Jurassic Ameghino (=Nordenskjöld) Formation at Longing Gap in the Antarctic Peninsula. The material was morphologically and chemically analyzed. We made a qualitative study and a taphonomic analysis of the specimens and tested paleobiological and paleoecological hypotheses. We conclude that the samples analyzed are coprolites and propose a new ichnotaxon, Antarctoscoprus longinensis ichnogen. and ichnosp. nov., characterized by being a small and flat coprolite differing from other ichnogenera by its composition, which consists mainly of actinopterygian remains (e.g., scales, vertebrae, skull bones, and teeth). Antarctoscoprus longinensis includes three morphotypes (i.e., circular, subcircular, and elongated) derived from an elongated three-dimensional original form by compactation. Based on the internal content, we infer the producers of the coprolites were carnivorous predators, putatively an ichthyophagous taxon. Due to the abundance of actinopterygians—mainly aspidorhynchids and ichthyodectids— and the size of the coprolites we propose macropredator fishes as the putative producers. The mainly undisrupted fish carcasses and coprolites allow us to conduct further studies that might lead to a better understanding of the ancient communities living in the Late Jurassic Sea that surrounded Antarctica.

Keywords

• Coprolites
• Actinopterygian remains
• Macropredator vertebrates
• West Antarctica
• Longing Gap