Chinese paleontologists have uncovered the fossilized skeleton of the colossal Mamenchisaurus dinosaurs, heralding a remarkable new genus from the late Jurassic epoch.

The newly identified species inhabited southwestern China approximately 147 million years ago (late Jurassic epoch).

Scientifically designated as Tongnanlong Zhimingi, this sauropod dinosaur measured around 23-28 m (75.5-92 feet) in length.

“Sauropods are enormous, herbivorous quadrupeds and represent the largest terrestrial dinosaurs that ever existed,” remarked Dr. Xuefang Wei, a researcher from the Western Center for China Geological Survey.

“They first appeared in the late Triassic period, spread globally by the Middle Jurassic, and ultimately went extinct at the end of the late Cretaceous period.”

More than 150 genera have been documented, including over 20 genera from the Jurassic period within China.

“Southwest China is a significant area for Jurassic sauropod discoveries, particularly in the Sichuan Basin,” they added.

The sauropod fauna found in the Jurassic Sichuan Basin was once considered an endemic population distinct from the terrestrial fauna of Pangaea.

This distribution was often explained by the East Asian seclusion hypothesis, suggested to have occurred between the Jurassic and early Cretaceous periods.

However, this hypothesis faces challenges from recent phylogenetic analyses conducted in China, as well as the discovery of Neosaurupod dinosaurs, including a Mamenchisaur dinosaur found in Africa.

The holotype specimen of Tongnanlong Zhimingi was excavated from a construction site in the Dongnan district of the Chonging region within the Sichuan Basin.

This includes three dorsal vertebrae, six caudal vertebrae, scapulae, coracoids, and hind limb bones.

“Our fieldwork indicates that the fossil site belongs to the upper part of the Jurassic. The Monitor formations are situated above Quaternary sediments,” noted the paleontologist.

“The Sorning Formation is composed of purple-red mudstone and sandstone.”

“The layer is rich in invertebrate fossils, including various freshwater Conchostracans, particularly ostracods and stone trails.”

Several vertebrates are identified from this layer, such as fish Ceratodus szechuanensis, turtle Plesiochelys Tatsuensis, and dinosaurs like Mamenchisaurus anyuensis.

Anatomical and phylogenetic studies affirmed that Tongnanlong Zhimingi is part of the sauropod dinosaur family Mamenchisauridae.

“Mamenchisauridae was not a fauna confined to East Asia, but rather had a global distribution during the late Jurassic period,” the researchers concluded.

“Tongnanlong Zhimingi enhances the diversity of Eusauraupods and offers new insights into sauropod diversity and evolutionary developments from the mid-Jurassic to the Late Jurassic as they increased in size.”

Their study was published in the journal Scientific Reports on July 10th.

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X. Wei et al. 2025. New Mamenchisaurus discoveries monitoring the Upper Jurassic formations in the Sichuan Basin, China and their implications for sauropod gigantism. Sci Rep 15, 24808; doi:10.1038/s41598-025-09796-0