Pliocene avian footprints from the Lake Eyre Basin, South Australia

摘要

The tetrapod trace fossil record of Australia has, until recently, been poorly studied relative to records on other continents. In the last few decades, a series of studies have revealed that these traces are more common than was previously thought. They have provided fossil evidence of taxa for which no skeletal fossils are known and have been found in areas of the country where no skeletal fossils occur. We describe a series of footprints from the Main Body Tirari Formation in the Lake Eyre Basin representing the first avian footprints published from the Australian Pliocene. Skeletal fossils from this member of the Tirari Formation are rare and are restricted to a few mammalian taxa. Three avian ichnotaxa are identified here, including Anatipeda alfi, Phoenicopterichnum isp., and Koreanaornis sirin (hamanensis), with several prints potentially belonging to a second species of Koreanaornis. We also clarify several contradictions relating to the relevant avian ichnotaxonomy and propose an unambiguous method for measuring digit divarication in avian footprints with curved digital traces. The footprints described here indicate that flamingos, a variety of waders, and swans or pelicans were present when the lacustrine sediments of the Main Body Tirari Formation were laid down. These prints highlight the potential for more trace fossils to be found in the region, from a time period poorly represented by body fossils.