''Qianjiangsaurus'' (meaning " Qianjiang lizard") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of

hadrosauroidea Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or Hadrosauridae, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Euro ...

n ornithopod dinosaurs from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Zhengyang Formation of China. The genus contains a single species, ''Q. changshengi'', known from a partial skeleton. ''Qianjiangsaurus'' is one of the few hadrosauroids named from south China, and it indicates important fauna connections between similarly aged formations in Mongolia.

Discovery and naming

The ''Qianjiangsaurus''

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, CLGRP V00016, was discovered by a paleontological expedition associated with the Chongqing Bureau of Geological and Mineral Resource Exploration and Development during the winter of 2022. The locality represents sediments of the Zhengyang Formation near Zhengyang area in

Qianjiang District Qianjiang District (), formerly Qianjiang Tujia and Miao Autonomous County, is a district (formerly an autonomous county), in the southeastern part of Chongqing, China, bordering Hubei province to the east and northeast. While it is governed as a d ...

Chongqing Municipality Chongqing Previously romanized as Chungking ();. is a direct-administered municipality in Southwestern China. Chongqing is one of the four direct-administered municipalities under the Central People's Government, along with Beijing, Shanghai ...

of southwest China. The specimen consists of a partial, somewhat articulated skeleton, comprising an incomplete

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

, four

dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...

, the sacrum, many

caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

and associated

chevrons Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock la ...

, most of the

pelvic girdle The hip bone (os coxae, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below. In some vertebrates (including humans before puberty) it is composed of three parts: the Ilium (bone) ...

, and several hindlimb bones. After being announced in August 2024 in a non-finalized

preprint In academic publishing, a preprint is a version of a scholarly or scientific paper that precedes formal peer review and publication in a peer-reviewed scholarly or scientific journal. The preprint may be available, often as a non-typeset versi ...

, Dai et al. (2025) described ''Qianjiangsaurus changshengi'' as a new genus and species of hadrosauroid dinosaurs based on these fossil remains. The generic name, ''Qianjiangsaurus'', combines "Qianjiang"—the name of the district containing the type locality—with the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''σαῦρος'' (), meaning . The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''changshengi'', Changsheng Wang, the discoverer of the Chongqing fossil locality. '' Nanningosaurus'', a genus from the Nalong Basin of

Guangxi Guangxi,; officially the Guangxi Zhuang Autonomous Region, is an Autonomous regions of China, autonomous region of the China, People's Republic of China, located in South China and bordering Vietnam (Hà Giang Province, Hà Giang, Cao Bằn ...

, is the only other hadrosauroid currently named from south China.

Description

The holotype of ''Qianjiangsaurus'' likely represents a mature adult individual. It is medium-sized in comparison to related taxa, at about long. The prepubic process of the pubis is fan-shaped, with a length:height ratio of about 0.79, representing the single

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a Synapomorphy, derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or Outgroup (cladistics), outgroup taxa, not ...

(unique derived trait) identified in the holotype. The unique combination of other characters includes a total of 30

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

tooth positions with no more than five teeth per

alveolus Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * M ...

(tooth socket), a coronoid process at a right angle to the dentary, and seven fused vertebrae in the sacrum. While some of its

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

(ancestral) anatomical features confidently place it within the Hadrosauroidea, it still demonstrates

apomorphic In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

(derived) features of later-diverging members of the Hadrosauridae, placing it as a

transitional form A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross ...

between the two groups.

Classification

In their

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, Dai et al. (2025) recovered ''Qianjiangsaurus'' as the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to the Mongolian ''

Plesiohadros ''Plesiohadros'' (meaning "near to hadrosaurids") is an extinct genus of hadrosauroid dinosaur. It is known from a partial skeleton including the skull collected at Alag Teg locality, from the Campanian Alagteeg Formation of southern Mongolia. ...

'', with these taxa as late-diverging members of the

Hadrosauroidea Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or Hadrosauridae, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Euro ...

outside of the

Hadrosauridae Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fam ...

. Their results are displayed in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

Paleoecology

The discovery of ''Qianjiangsaurus'' provides further support for several faunal similarities between the Zhengyang Formation of China and the Djadokhta and Baruungoyot formations of Mongolia. These dinosaur parallels may indicate a faunal interchange between the two regions during the end of the Late Cretaceous, from the late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

–early

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

. While

absolute dates Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy ...

have yet to be determined for the Zhengyang Formation, it was likely deposited during this time. ''Qianjiangsaurus'' is the first distinct dinosaur taxon to be named from the Zhengyang Formation. Fragmentary specimens belonging to unnamed

titanosaurs Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

and theropods (including

tyrannosauroids Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...

and putative

carnosaurs Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods. While Carnosauria was historically considered largely synonymous with Allosauroidea, some recent studies have revived Carn ...

) have also been found. Since large-scale excavations had not occurred in the region until 2022, additional specimens—such as

ornithomimosaurs Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period (geology), Period of Laurasia (now Asia ...

, therizinosauroids,

oviraptorosaurs Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or wi ...

as seen in coeval formations—may be found in the future.

References

{{Taxonbar, from1=Q129891986, from2=Q129892002 Hadrosauroidea Dinosaur genera Late Cretaceous dinosaurs Fossil taxa described in 2025 Dinosaurs of China

Discovery and naming

Description

Classification

Paleoecology

See also

References