A bizarre new genus and species of ornithomimid dinosaur has been identified from the fossilized remains found in 2014 in Coahuila, Mexico.
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Life reconstruction of Mexidracon longimanus. Image credit: Ddinodan / CC BY 4.0.
The newly-identified dinosaur species roamed Earth during the Late Cretaceous epoch, some 73 million years ago.
Named Mexidracon longimanus, the ancient creature was around 3 m (10 feet) in length.
It belongs to Ornithomimidae, a family of theropod dinosaur that evolved a toothless beak and were likely omnivorous or herbivorous, superficially resembling living ostriches.
“Ornithomimosaurs are a clade of ostrich-like theropod dinosaurs characterized by relatively small and delicate skulls with large orbits, long necks, elongated forelimbs with non-raptorial manus and long cursorial hindlimbs,” said Dr. Claudia Inés Serrano-Brañas, a paleontologist at Smithsonian Institution, the Universidad de Ciencias Geológicas y Sociales and the Benemérita Escuela Normal de Coahuila, and her colleagues from the United States, Mexico and Spain.
“Body size can range from small forms (over 12 kg), such as Nqwebasaurus thwazi and Hexing qingyi from the Early Cretaceous of Africa and Asia, respectively, to the large Late Cretaceous Asian species Deinocheirus mirificus (6 tons).”
“Ornithomimosaurs are known from Cretaceous geological formations in Europe, Asia, North America and Africa.”
The fossils of Mexidracon longimanus were discovered in 2014 in the Cerro del Pueblo Formation in Mexico.
“The Cerro del Pueblo Formation in the state of Coahuila represents one of the richest dinosaur-bearing formations from Mexico,” the researchers said.
“As in other Upper Cretaceous formations of North America and Asia, ornithomimosaur remains are quite common in the Cerro del Pueblo Formation.”
“However, the majority of these specimens are highly fragmentary, and even relatively complete specimens have not been formally described.”
“Mexidracon longimanus represents the second ornithomimosaur and the first ornithomimid dinosaur species formally described from the Cerro del Pueblo Formation.”
The most conspicuous autapomorphy of the new species is the extreme lengthening of its metacarpus, the bones that form the palm.
“The finding of Mexidracon longimanus adds to the increasing diversity and paleobiogeographic distribution of the group during the Campanian of southern Laramidia,” the scientists said.
“The ornithomimosaur record of the Cerro del Pueblo Formation represents yet another instance of the coexistence of ornithomimids and deinocheirids spanning a wide range of body sizes within this clade of ‘ostrich’ dinosaurs.”
The discovery of Mexidracon longimanus is reported in a paper published this week in the journal Cretaceous Research.
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Claudia Inés Serrano-Brañas et al. A long-handed new ornithomimid dinosaur from the Campanian (Upper Cretaceous) Cerro del Pueblo Formation, Coahuila, Mexico. Cretaceous Research, published online January 28, 2025; doi: 10.1016/j.cretres.2025.106087
