Ostrich-like eggshells from a 10.1 million-yr-old Miocene ape locality, Haritalyangar, Himachal Pradesh, India

Abstract

We report fossil ratite eggshells from the site, Dharamsala of Dhok Pathan Formation (Middle Siwaliks), dated to 10.1 Ma. A comparative analysis reveals that in their combination of eggshell surface, pore, pore canal morphology and cross-sectional features, the Indian eggshells show closest affinity with the widely distributed Neogene fossil taxon Struthiolithus, and as such are assigned to cf. Struthiolithus. We have carried out a parsimony analysis of all relevant extinct and extant palaeognathous birds of the southern continents, as ingroup taxa. Genyornis, an extinct bird from Australia, and Gallus gallus (chicken) were also used in this analysis as ingroup (Neornithes) taxa. The result supports monophyly of Palaeognathae. The present cf. Struthiolithus eggshell and Aepyornis were found to be sister taxa and their forbearers had a common ancestry with Afro-Arabian Struthio and Diamantornis. The Indian subcontinent now has an extended fossil record of struthionid eggshells from the Late Miocene to the Late Pleistocene, implying dispersals through intercontinental migration corridors. Our stable carbon isotope (δ¹³C_PDB) value of −10.4‰ of the present eggshells suggests that the ratite bird had a diet mainly of C₃ plants.