Dubbed Archaeocursor asiaticus, the newly-discovered species is the earliest-diverging ornithischian dinosaur yet discovered in Asia, according to a team of paleontologists from China.
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Archaeocursor asiaticus. Image credit: Yao et al., doi: 10.1016/j.isci.2024.111641.
Archaeocursor asiaticus lived in what is now southwestern China during the Early Jurassic, some 193 million years ago.
This dinosaur was around 1 m (3.3 feet) in length and belonged to a group of plant-eating dinosaurs called Ornithischia.
“Ornithischia, a prominent clade of dinosaurs, diversified into various forms such as ankylosaurs, stegosaurs, hadrosaurs, ceratopsians, and pachycephalosaurs throughout the Mesozoic Era,” said Yunnan University paleontologist Xi Yao and colleagues.
“Alongside other non-avian dinosaurs, they faced extinction at the close of the Cretaceous, while their early evolutionary history remains debated.”
“During the Early Jurassic, ornithischian fossils are plentiful and diverse in the supercontinent Gondwana.”
“In contrast, the ornithischian fossil record in Laurasia during this time is less varied and primarily comprises armored dinosaurs.”
A nearly complete left femur of Archaeocursor asiaticus was found at the Ziliujing Formation, approximately 2 km (1.2 miles) north of Chongqing Central Park in Yubei district, Chongqing, southwestern China.
According to the team, the new species exhibits affinities with Gondwanan species, Eocursor parvus.
The discovery points to an earlier dispersal event of Early Jurassic ornithischian dinosaurs from Gondwana to Laurasia, including East Asia, which appears to be independent of, and possibly earlier than, the dispersal of armored dinosaurs.
“The new phylogenetic topology proposed in the study suggests an additional independent dispersal of ornithischian dinosaurs into East Asia during the Early Jurassic,” the researchers said.
“The close relationship between Archaeocursor asiaticus and Eocursor parvus, despite their distant habitats, suggests a probable origin from Gondwana, followed by northward migration to Laurasia and eventually to East Asia during the Pliensbachian age.”
“This timing might precede the arrival of armored dinosaurs in the region.”
“Moreover, this new topology hypothesizes the existence of a previously unrecognized cosmopolitan clade of early ornithischian dinosaurs, positioned phylogenetically between Heterodontosauridae and Thyreophora.”
“Nevertheless, due to the fragmentary nature of the Archaeocursor asiaticus holotype, support for this clade remains tentative, awaiting further fossil discoveries.”
The team’s paper was published this month in the journal iScience.
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X. Yao et al. New evidence for the earliest ornithischian dinosaurs from Asia. iScience, published online December 19, 2024; doi: 10.1016/j.isci.2024.111641
