The exceptionally long neck of Lijiangosaurus yongshengensis contained 42 cervical vertebrae, according to a research team led by paleontologists from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.
Reconstruction of nothosaurs about 240 million years ago revealing a hidden diversity from southwestern China: Lijiangosaurus yongshengensis (center), Nothosaurus yangjuanensis (upper left), Nothosaurus luopingensis (upper right), Brevicaudosaurus jiyangshanensis (lower left), and Lariosaurus hongguoensis (lower right). Image credit: Kelai Li.
Lijiangosaurus yongshengensis inhabited the Middle Triassic seas between 247 and 241 million years ago.
The ancient creature was a type of nothosaur, a clade of marine sauropterygian reptiles.
Nothosaurs could grow up to 7 m (23 feet) long and swam using four paddle-like limbs.
They had flattened skulls with a meshwork of slender conical teeth that were used to catch fish and squid.
“Sauropterygia arose as a major marine reptilian clade during the Early to Middle Triassic, persisting as key components of the Mesozoic marine ecosystem for approximately 180 million years,” said lead author Dr. Qinghua Shang and colleagues.
“The early-diverging sauropterygians include placodonts, pachypleurosaurs, nothosaurs, and early pistosaurs.”
“Plesiosaurs, a symbolic group of extinct reptiles, represent a late-diverging clade from pistosaurs within Sauropterygia.”
“The nothosaurs are equal to nothosaurians in systematic paleontology, which not only encompass the family Nothosauridae (Nothosaurus and Lariosaurus), but also other species within Nothosauria.”
“Despite numerous described species, nothosaurs display lower diversity at the genus level and in anatomical morphology compared to other sauropterygian subgroups.”
“The body sizes of nothosaurs are typically larger than pachypleurosaurs but smaller than pistosaurs, including plesiosaurs.”
Lijiangosaurus yongshengensis had a small skull and a body length of over 2.5 m (8 feet).
It evolved an exceptionally long neck with 42 cervical vertebrae, twice the number observed in most coeval sauropterygians.
“Plesiosaurs are usually characterized by their spectacularly long necks,” the paleontologists said.
“Despite the secondary development of short necks in some later-diverging plesiosaurian species, early plesiosaurs and their Triassic ancestral kin, the early pistosaurs, possess impressive elongate necks when the number of cervical vertebrae over 30 is suggested as a synapomorphy of early pistosaurs and plesiosaurs.”
“Following this traditional view, we consider only a neck with more than 30 cervical vertebrae as a long or elongate neck in our study.”
“This iconic character in plesiosaurs is distinctive in secondarily marine tetrapods, when other representatives like ichthyosaurs, thalattosuchians, mosasaurs, and cetaceans are all short-necked and more fish-like.”
The fossilized skeleton of Lijiangosaurus yongshengensis was found at a previously unknown early Middle Triassic locality of the Beiya Formation in China’s Yunnan province near the eastern Tibetan Plateau and northern Myanmar.
“This site differs from the previously documented fossil-rich regions in southwestern China around the boundary between Yunnan and Guizhou provinces,” the researchers said.
Lijiangosaurus yongshengensis represents the earliest known sauropterygian reptile evolving an exceptionally long neck with 42 cervical vertebrae.
“Our discovery demonstrates that extreme cervical elongation developing more than 30 cervical vertebrae emerged in sauropterygians prior to the rise of plesiosaurs and their pistosaur ancestors,” the scientists said.
“Furthermore, Lijiangosaurus yongshengensis possesses a unique type of accessory intervertebral articulation compared with other reptiles, and we attribute this structure to reducing body undulation.”
“This discovery increases the known diversity of accessory intervertebral articulations in reptiles, and underscores the high plasticity of the vertebral column in the early evolution of sauropterygians.”
The team’s paper appears in the journal Communications Biology.
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W. Wang et al. 2025. Earliest long-necked sauropterygian Lijiangosaurus yongshengensis and plasticity of vertebral evolution in sauropterygian marine reptiles. Commun Biol 8, 1551; doi: 10.1038/s42003-025-08911-1
