Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, 94720, USA.
Department of Paleontology, San Diego Natural History Museum, San Diego, CA, 92182, USA.
Sci Rep. 2020 Oct 26;10(1):18286. doi: 10.1038/s41598-020-75248-6.
While pelagornithid or 'bony-toothed' bird fossils representing multiple species are known from Antarctica, a new dentary fragment of a pelagornithid bird from the middle Eocene Submeseta Formation on Seymour Island, Antarctica represents a species with a body size on par with the largest known species in the clade. Measurements from the partial 'toothed' dentary point to a giant body size for the species, although the spacing among the pseudoteeth differs from that published for other pelagornithids. The discrepancy might suggest that previous techniques are not adequate for examination of incomplete material or that another factor such as phylogeny might impact size estimates and comparisons. Combined with a revised stratigraphic position in the early Eocene La Meseta Formation on Seymour Island for the largest pelagornithid tarsometatarsus known, these Antarctic fossils demonstrate the early evolution of giant body size in the clade (by ~ 50 Ma), and they likely represent not only the largest flying birds of the Eocene but also some of the largest volant birds that ever lived (with an estimated 5-6 m wingspan). Furthermore, the distribution of giant-sized pelagornithid fossils across more than 10 million years of Antarctic geological deposits points to a prolonged survival of giant-sized pelagornithids within the southern seas, and their success as a pelagic predatory component of marine and coastal ecosystems alongside early penguins.
尽管已经知道有来自南极洲的多个种属的 pelagornithid 或“骨齿”鸟类化石，但在南极洲的 Seymour 岛上中始新世的 Submeseta 组发现的一块 pelagornithid 鸟类的新齿骨碎片代表了一个体型与该分支中最大已知物种相当的物种。来自部分“有齿”齿骨的测量结果表明，该物种体型巨大，尽管假齿之间的间距与其他 pelagornithids 公布的数据不同。这种差异可能表明，以前的技术不足以检查不完整的材料，或者其他因素（如系统发育）可能会影响大小估计和比较。再加上在 Seymour 岛上的早始新世 La Meseta 组中修订的最大 pelagornithid 跗跖骨的地层位置，这些来自南极洲的化石证明了该分支中巨大体型的早期进化（约在 5000 万年前），它们可能不仅代表了始新世最大的飞禽，而且还代表了有史以来最大的飞鸟之一（翼展估计为 5-6 米）。此外，巨型 pelagornithid 化石在超过 1000 万年的南极地质沉积物中的分布表明，巨型 pelagornithids 在南部海域中长时间生存，并与早期企鹅一起成功成为海洋和沿海生态系统中的远洋掠食性组成部分。
