In a new study published in the journal PLoS ONE, paleontologists analyzed the fossilized remains of the alvarezsaurid dinosaur Bonapartenykus from the Allen Formation of Patagonia. Their results shed new light on the body plan of Bonapartenykus and other members of the alvarezsaurid dinosaur group Patagonykinae.
Life reconstruction of an individual of Bonapartenykus from the locality of Salitral Ojo de Agua of the Allen Formation, Patagonia, Argentina. Image credit: Abel G. Montes.
Bonapartenykus lived in what is now Patagonia, Argentina, approximately 70 million years ago (Cretaceous period).
First described in 2012, this dinosaur belongs to one of the most mysterious groups of dinosaurs, called the Alvarezsauridae.
With another Patagonian genus, Patagonykus, Bonapartenykus forms a small alvarezsaurid clade, the Patagonykinae.
“Alvarezsauria is a group of later-diverging coelurosaurian theropod dinosaurs of medium to small size, whose fossil record spans from the Late Jurassic to the Late Cretaceous,” said Universidad Nacional de Río Negro paleontologist Jorge Gustavo Meso and colleagues.
“The distribution of this clade was likely originally Laurasian since its earliest known members are currently restricted to the Oxfordian (Late Jurassic) of China.”
“The Early Cretaceous fossil record of Alvarezsauria was also limited to the Asian continent, which now consists of up to three species.”
“By the Late Cretaceous, Alvarezsauria was highly diversified and globally distributed, with abundant Laurasian records from what is now Asia, Europe, and North America as well as the first Gondwanan records represented by discoveries from South America.”
“Patagonykinae is the only named South American clade of alvarezsaurids that clusters Patagonykus and Bonapartenykus.”
In their new study, Dr. Gustavo Meso and co-authors examined a large number of alvarezsaurid fossils from the Salitral Ojo de Agua locality of the Patagonian Allen Formation.
“Although these specimens were collected at different times without precise original provenance information, we gathered X-ray diffraction data of the associated sediments that now suggests that all of these specimens come from the same site and stratigraphic level as the holotype of the alvarezsaurid Bonapartenykus ultimus,” the paleontologists said.
“Based on this new provenance information and the morphological similarity of the considered specimens, we tentatively refer them to the genus Bonapartenykus.”
According to the authors, the newly-described specimens shed light on the body plan of Patagonykinae by permitting a more complete reconstruction of their neck, pectoral girdle, hindlimb, and tail.
“While our results favor a monospecific alvarezsaurid assemblage for the moment, future research and quarrying efforts at the Salitral Ojo de Agua locality may unearth evidence that can further test our current interpretation,” they said.
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J.G. Meso et al. 2025. New information on Bonapartenykus (Alvarezsauridae: Theropoda) from the Allen Formation (middle Campanian-lower Maastrichtian) of Río Negro Province, Patagonia, Argentina clarifies the Patagonykinae body plan. PLoS ONE 20 (1): e0308366; doi: 10.1371/journal.pone.0308366
Source : Breaking Science News