A new genus and species of enantiornithine bird has been described from a partial right humerus found in southern Patagonia, Argentina.
The newly-described bird species lived in Argentinian Patagonia during the Maastrichtian age of the latest Cretaceous, between 70 and 66 million years ago.
Scientifically named Yatenavis ieujensis, the species was relatively small, about the size of a sparrow.
It represents the southernmost and one of the youngest occurrences of Enantiornithes, the most diverse group of birds known in the Cretaceous period.
“Enantiornithes were the most widespread and diverse group of Mesozoic birds, occupying various ecological niches, comparable with the extant Neornithes,” said Dr. Gerardo Álvarez Herrera, a paleontologist at the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ and CONICET, and his colleagues from Argentina and Japan.
“Their fossil record is rich in the Early Cretaceous, principally from key localities such as Jehol, Changma, and Las Hoyas.”
“The fossil remains from these localities provide valuable information about the diversity and early evolution of these birds, despite that they are often compressed and preserved in two dimensions.”
“Nevertheless, these birds have a relatively scarce record in the Late Cretaceous,” they added.
“In South America, however, the opposite is the case, that is, the Early Cretaceous enantiornithines are poorly represented whereas their record comes mostly from the Late Cretaceous beds.”
The distal half of a right humerus of Yatenavis ieujensis was found in the outcrop of the Chorrillo Formation at Estancia La Anita in the Argentinian province of Santa Cruz.
“Yatenavis ieujensis shares morphological features with Late Cretaceous enantiornithines found at diverse localities, including Madagascar, North America, Patagonia, and Central Asia,” the paleontologists said.
“The morphological similarities between species coming from such distant localities may indicate the presence of a Late Cretaceous enantiornithine subclade widely distributed across the ancient supercontinents Gondwana and Laurasia.”
According to the team, Yatenavis ieujensis coexisted with small non-avialan dinosaurs, sphenodonts, terrestrial gastropods, fishes, frogs, mammals, snakes, turtles, and other birds.
“The new information indicates that during time of deposition of the Chorrillo Formation, coexisted at least three different kind of birds: the derived ornithurine Kookne yeutensis, a very large-sized enantiornithine, and the smaller Yatenavis ieujensis,” the authors said.
“This information may indicate that latest Cretaceous enantiornithines from Patagonia were more diversified than previously hypothesized.”
“Yatenavis ieujensis constitutes the southernmost occurrence for Enantiornithes worldwide,” they concluded.
“Despite its fragmentary nature of the recovered humerus, it clearly indicates that it represent one of the smallest enantiornithine birds of the Late Cretaceous in South America.”
“The discovery of Yatenavis ieujensis in the Chorrillo Formation demonstrates that enantiornithines were also abundant in the high latitudes of the southern hemisphere during the latest Cretaceous.”
Yatenavis ieujensis is described in a paper in the journal Cretaceous Research.
Gerardo Álvarez Herrera et al. New enantiornithine bird from the uppermost Cretaceous (Maastrichtian) of southern Patagonia, Argentina. Cretaceous Research, published online December 16, 2022; doi: 10.1016/j.cretres.2022.105452
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