First mammal tracks from the Eocene of Antarctica

A manus-pes set imprint is described from the early Eocene Fossil Hill Formation in the Fildes Peninsula, King George Island, Antarctica. The tracks were identified during a comprehensive review of the trace fossil assemblage within Antarctic Specially Protected Area (ASPA) 125a. Based on their general morphology, although a confident ichnotaxonomic assignment is not possible, the tracks are interpreted as having been produced by a terrestrial carnivorous mammal, most likely attributable to a small sparassodontan metatherian, thereby representing the first possible taxonomic record of the clade from Antarctica. This discovery provides the first evidence of a Paleogene terrestrial mammal beyond Seymour (Marambio) Island and constitutes the earliest ichnological record of a carnivorous mammal from Antarctica. As such, it not only expands the known paleogeographic distribution of Antarctic Paleogene mammals but also provides the first direct evidence that mammalian predators formed part of the continent’s terrestrial ecosystems during the Eocene. The inferred presence of a small sparassodontan predator adds a previously unrecognized component to Antarctic terrestrial food webs, filling a major gap in current reconstructions of Eocene trophic structure. Previous reconstructions of Antarctic Eocene terrestrial ecosystems identified phorusrhacid “terror birds” as the only documented terrestrial predators. The addition of a small sparassodontan indicates that these ecosystems supported a more taxonomically diverse carnivore assemblage and a more complex trophic structure than previously recognized.