A new genus and species of unenlagiine dinosaur has been identified by paleontologists in Argentina. Named Diuqin lechiguanae, it fills a substantial gap in the fossil record of these theropod dinosaurs.
Life reconstruction of Diuqin lechiguanae. Image credit: Porfiri et al., doi: 10.1186/s12862-024-02247-w.
Diuqin lechiguanae roamed our planet during the Santonian age of the Cretaceous period, between 86 and 84 million years ago.
This species belonged to Unenlagiine, a subfamily of long-snouted paravian theropods within the family Dromaeosauridae.
“Unenlagiines are Gondwanan predatory dinosaurs that are nested within Paraves, the clade that includes birds and their closest non-avian theropod relatives,” said Dr. Juan Porfiri from the Universidad Nacional del Comahue, Buenos Aires, and his colleagues.
“The unenlagiine fossil record comes predominantly from Argentina, where the greatest number of specimens and the most complete skeletons have been found, although other materials at least tentatively assigned to Unenlagiinae have also been recovered from Brazil, Chile, Colombia, and Antarctica.”
“The small-bodied, potentially volant Madagascan theropod Rahonavis ostromi has also been frequently regarded as an unenlagiine, depending on the specific phylogenetic hypothesis employed.”
“Unenlagiines are most frequently interpreted as early diverging dromaeosaurids, although other authors have instead regarded these theropods as a distinct paravian clade (Unenlagiidae).”
“They are an important clade for understanding bird origins due to their close phylogenetic relationship with Avialae.”
“Unfortunately, however, most species are represented only by fragmentary fossils.”
Diuqin lechiguanae’s fragmentary but associated postcranial skeleton was recovered from the Bajo de la Carpa Formation of Neuquén Province, Patagonia, Argentina.
“The specimen was collected from the isthmus between the southeast coast of Lago Barreales and the northwest coast of Lago Mari Menuco, in Neuquén Province,” the paleontologists said.
According to the authors, Diuqin lechiguanae is the first species of unenlagiine dinosaur to be discovered from the Bajo de la Carpa Formation.
“The Bajo de la Carpa Formation has yielded fossils that collectively represent a diverse and important paleobiota,” they said.
“Vertebrate remains are abundant and often well-preserved, and include those of snakes, lizards, turtles, crocodyliforms, indeterminate pterosaurs, ornithopods, titanosaurian sauropods, non-avian theropods, and birds.”
Diuqin lechiguanae fills a temporal gap of at least 15 million years in the fossil record of unenlagiines (conservatively, 90-75 million years, possibly greater).
“The new species augments the fossil record of South American unenlagiines by filling a significant gap in their temporal distribution,” the researchers said.
“Preserved elements of Diuqin lechiguanae show morphological differences from corresponding bones in other unenlagiine species, such as an accessory lamina on the posteriormost sacral vertebral neural arch, distinctive paired foramina on the posteriormost sacral and anterior caudal neural arches, and a humerus with a distally placed distolateral deltopectoral ridge and several conditions that appear intermediate between the humeri of Unenlagia spp. and the exceptionally large-bodied unenlagiine Austroraptor cabazai.”
“Coupled with the multi-million-year stratigraphic gaps between Diuqin lechiguanae and geologically older and younger unenlagiines, respectively, these anatomical distinctions support the validity of the new species.”
“Further, the humerus of the Diuqin lechiguanae type specimen exhibits two conical tooth marks that indicate that the carcass was fed upon by another tetrapod, likely a crocodyliform, mammal, or theropod (perhaps the megaraptorid represented by a tooth found at the same site, or even another unenlagiine individual, potentially a member of the same species).”
The discovery of Diuqin lechiguanae is reported in a paper in the journal BMC Ecology and Evolution.
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J.D. Porfiri et al. 2024. Diuqin lechiguanae gen. et sp. nov., a new unenlagiine (Theropoda: Paraves) from the Bajo de la Carpa Formation (Neuquén Group, Upper Cretaceous) of Neuquén Province, Patagonia, Argentina. BMC Ecol Evo 24, 77; doi: 10.1186/s12862-024-02247-w
