The Genyornis Egg: Response to Miller et al.’s commentary on Grellet-Tinner et al., 2016

Williams (1981) and Williams and Rich (1991) attributed Australian Quaternary fossil eggshell that differed from that of emu Dromaius novaehollandiae to the extinct bird Genyornis newtoni without any osteological or embryonic support. Such association by proximity or abundance mirrors the case of the mistaken association of oviraptor eggs to Protoceratops in the 1920's by Andrews (Grellet-Tinner and Makovicky, 2006). No other candidate species was considered, and this attribution has been unchallenged and followed by everyone thereafter. Much research has been done on this Australian eggshell, with one result being that the extinction of the parent of this eggshell is the most well documented for a taxon in Australia (e.g., Miller et al., 1999, Miller et al., 2005). Grellet-Tinner et al. (2016) raised several problems with the identity of the eggshell Williams (1981) attributed to Genyornis newtoni and suggested that extinct megapodes of the genus Progura were the more likely layer of this eggshell type, therein referred to as “putative Genyornis oological material” (PGOM). Miller et al. (2017) challenged our hypothesis stating that “Based on the dimensions of the reconstructed Spooner Egg, Grellet-Tinner et al. (2016) argue that PGOM is too small for a bird with the body mass estimated for Genyornis (168–275 kg) … …[and] …. None of the additional PGOM observations reported by Grellet-Tinner et al. (2016) are inconsistent with a Genyornis parent”. Here we take the opportunity to respond to their critique, the basis of which resolves into a few points, which we address in turn.