Paleontologists in China have found the fossil fragments from a new genus and species of stegosaurian dinosaur: Baiyinosaurus baojiensis.
Life reconstuction of Gigantspinosaurus (bottom foreground), a sister species of the newly-discovered stegosaur Baiyinosaurus baojiensis, and and other dinosaurs from the Shaximiao Formation. Image credit: A. Belov / CC BY-SA 3.0.
Baiyinosaurus baojiensis roamed Earth during the Middle Jurassic epoch, about 165 million years ago.
This dinosaur species was a member of Stegosauria, a group of plant-eating armored dinosaurs that lived during the Jurassic and Cretaceous periods.
Stegosaurs reached a maximum length of about 9 m (30 feet). They had small heads, peg-like teeth, vertical bony plates and spines on their back and tail, and hoof-like toes on all four limbs.
“Stegosaurs are a minor but iconic clade of ornithischian dinosaurs, yet due to a poor fossil record, their early evolution is poorly understood,” said Dr. Li Ning from the China University of Geosciences and colleagues.
“These dinosaurs are characterised by the possession of two parasagittal rows of hypertrophied dermal armor plates and/or spines extending from the neck to the end of the tail and have been found on all continents except for Antarctica and Australia.”
“The earliest stegosaurs are from the Middle Jurassic, they achieved a global distribution by the Late Jurassic and subsequently waned in diversity during the Early Cretaceous.”
“Records of stegosaurs from the Middle Jurassic are rare, including only five species: Loricatosaurus from the United Kingdom, Isaberrysaura from Argentina, Adratiklit from Morocco, and Huayangosaurus and Bashanosaurus from China.”
The partial skeleton of Baiyinosaurus baojiensis — comprising a partial cranium, one cervical vertebra, seven dorsal vertebrae and one caudal vertebra — was discovered in the Wangjiashan Formation.
“The study area is located in the northwestern part of the Baojishan Basin, belonging to the Pinchuan District of Baiyin City, Gansu Province, China,” the paleontologists said.
“The Baojishan Basin is at the eastern end of the Qilian Mountains.”
The team’s systematic analysis shows that Baiyinosaurus baojiensis is an early-diverging stegosaur related to Isaberrysaura, Alcovasaurus, Jiangjunosaurus and Gigantspinosaurus.
“Baiyinosaurus baojiensis has some plesiomorphic characteristics and is transitional in morphology between early thyreophorans and early-diverging stegosaurs,” the researchers said.
“The increasing diversity of Middle Jurassic stegosaurs that also occupy early-diverging positions indicates that it is likely that the stegosaurs split from their sister taxon, the ankylosaurs, early in the Middle Jurassic (or much earlier).”
The study was published in the journal Scientific Reports.
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L. Ning et al. 2024. A new stegosaur (Dinosauria: Ornithischia) from the Middle Jurassic of Gansu Province, China. Sci Rep 14, 15241; doi: 10.1038/s41598-024-66280-x
Source : Breaking Science News