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Paleontologists have described new pelagornite bird fossils from the Central Eocene Submeseta formation on the island of Seymour, Antarctica.
An artist’s depiction of ancient albatross harassing a pelagornith as penguins romp in the oceans around Antarctica 50 million years ago. Image credit: Brian Choo.
Pelagornithids are an extinct group of large flying birds with a fossil record ranging from the late Paleocene to the late Pliocene and a global distribution.
Also known as bony-toothed birds, they had bony projections, or struts, on their jaws that resemble pointed teeth, although they are not true teeth.
Called pseudotes, the struts helped birds catch squid and fish from the sea as they hovered for perhaps weeks at a time over much of Earth’s oceans.
Although a much smaller pelagornitid fossil dates back 62 million years, one of the specimens just described – a 50-million-year-old portion of bird’s foot (tarsus metatarsus) – shows that larger pelagornites arose soon after life. rebounded from the end – Secret Mass Extinction 66 million years ago, when non-avian dinosaurs went extinct.
The second pelagornitid fossil from Seymour Island, part of a jawbone, dates back to about 40 million years ago.
“Our fossil discovery, with its estimate of a wingspan of 5-6 m (16-20 ft) shows that birds evolved to truly gigantic sizes relatively quickly after the extinction of the dinosaurs. and they have ruled the oceans for millions of years, “said lead author Peter Kloess, a graduate student at the University of California, Berkeley.
The fossils described by Kloess and colleagues are among many collected in the mid-1980s on the island of Seymour, off the northernmost tip of the Antarctic Peninsula.
They examined the pelagornitid tarsus and realized it came from an older geological formation than initially thought.
This meant that the fossil was about 50 million years old instead of 40 million years old. It is the largest known specimen for the entire extinct group of pelagornites.
The other fossil found, the central portion of the lower jaw, has preserved parts of its pseudotes. They would have been up to 3 cm (1 inch) tall when the bird was alive.
The preserved jaw section of approximately 12 cm (5 in) came from a very large skull that would have been up to 60 cm (2 ft) long.
Using measurements of the size and spacing of those teeth and analytical comparisons with other pelagornithid fossils, paleontologists were able to show that this fragment came from a single bird as large, if not larger, than the largest known skeletons of bone teeth. group of birds.
“These Antarctic fossils demonstrate the initial evolution of the giant body size in this clade (from 50 million years ago),” the researchers said.
“They probably represent not only the largest flying birds of the Eocene period, but also some of the largest flying birds that ever lived.”
Furthermore, the distribution of giant-sized pelagornithid fossils in over 10 million years of Antarctic geological deposits indicates a prolonged survival of giant-sized pelagornithids in the southern seas and their success as a pelagic predatory component of marine and coastal ecosystems alongside early penguins. . “
The team document was published in the journal Scientific reports.
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PA Kloess et al. 2020. First fossils of giant-sized bony-toothed birds (Aves: Pelagornithidae) from the Eocene of Seymour Island, Antarctica. Ski Rep 10, 18286; doi: 10.1038 / s41598-020-75248-6
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