Recently, a team led by Wu Wenhao from our center, in collaboration with the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Peking University, and other institutions, has established a new genus and species of salamander—Changchunerpeton nonganensis，based on atlantal and limb-bone specimens from the Late Cretaceous Nenjiang Formation in Jilin Province. This discovery extends the earliest fossil record of the hynobiid crown group back approximately 110 million years from the Miocene of Eastern Europe, providing important evidence for understanding the early evolution of salamanders, the developmental mechanisms of the head–neck joint, and their ecological adaptations. The findings have been published in the international academic journal Papers in Palaeontology.
Caudate amphibians, commonly known as salamanders, are a group of lissamphibians possessing both limbs and tails. Owing to their relatively conservative body plan, diverse ecological habits, and highly differentiated developmental patterns, salamanders serve as an important model group for studying the macroevolution and functional morphological adaptations of tetrapods. Molecular evidence indicates that the Late Cretaceous was a critical period in the evolution of the crown group of modern salamanders, during which multiple family-level taxa may have originated. However, although numerous beautifully preserved salamander fossils have previously been found in Middle Jurassic to Early Cretaceous strata in China, the Late Cretaceous strata had long lacked any relevant records, which has limited our understanding of this key evolutionary stage.
Changchunerpeton nonganensis discovered in this study was recovered from Late Cretaceous strata located about 40 kilometers southwest of Nong’an County, Changchun City, Jilin Province. Based on a holotype atlantal (cervical vertebra) specimen, three humeri, and one femur, together with the morphological features of the bones, the research team assigned the taxon to the hynobiid crown group. Its atlas bears the typical characteristics of the Hynobiidae, while also retaining a unique combination of morphological features that distinguish it from extant hynobiid members, providing new fossil evidence for understanding the early morphological evolution of the family.
Figure 1. Known distributions of salamander genera and species from the Triassic to the Cretaceous north of 38°N latitude in Asia.
Changchunerpeton nonganensis, the first Late Cretaceous salamander from East Asia, was discovered in Jilin Province, China.
Scale bar, 2,000 km.
The study further focused on the evolution of the head–neck joint in salamanders. The atlas is located at the junction between the skull and the vertebral column, and its morphology directly determines the mode of connection and the mobility between the head and the neck. By comparing a large number of extant and fossil lissamphibian specimens, the research team found that the atlantal intercotylar tubercle–an important structure situated at the anterior end of the atlas that forms the head–neck joint–is not a fixed feature inherited from the ancestor of lissamphibians. Rather, during the early evolution of different lineages, it shows a trend of gradual emergence and enlargement from an initially absent state.
Figure 2. High-resolution computed tomography renderings of the atlas of the holotype specimen of Changchunerpeton nonganensis (RCPS VJ4001). The left and right anterior cotyles (acot) of the atlas articulate with the paired occipital condyles; the atlantal intercotylar tubercle (igt), situated between the two articular surfaces, articulates with the occipital arch as an anterior extension of the vertebral centrum. Scale bar, 1 mm.
Figure 3. In the atlas of Changchunerpeton nonganensis, the notochordal canal extends from the posterior part of the vertebral centrum to the base of the atlantal intercotylar tubercle;
from posterior to anterior, the canal exhibits, in cross-section, a feature of bilateral constriction with earlier closure on the ventral side. Scale bar, 1 mm.
The study also revealed two distinct patterns of ossification development in the atlantal intercotylar tubercle of salamanders: stem-group salamanders mainly exhibit “transverse fissure” formation around the concavity of the notochordal canal, whereas crown-group salamanders display “longitudinal fissure” formation that gradually heals into a complete tubercle. This shift in developmental pattern may have influenced the stability and flexibility of the head–neck joint, offering a new perspective for exploring the functional morphological evolution of the head–neck joint in amphibians and their mechanisms of adaptation to aquatic and terrestrial environments.
In addition, the research team found that the bony processes within the atlantal neural canal, which serve to support the spinal cord, show a certain correlation with the ecological habits of lissamphibians. In caecilians and most aquatic salamanders, these processes may help suspend and anchor the spinal cord during burrowing or underwater locomotion, whereas in terrestrial salamanders, they may function more prominently as supports. This indicates that the atlas not only provides taxonomic information for identification but may also preserve evolutionary clues to an animal’s mode of locomotion and ecological adaptation.
Figure 4. High-resolution computed tomography renderings of the humerus (A–R) and femur (S–X) of Changchunerpeton nonganensis. The dorsal (crd) and ventral (crv) crests of the humerus, as well as the trochanter (trc) of the femur, are morphologically similar to those of extant hynobiids but differ from those of cryptobranchids.
Figure 5. Comparisons of atlas morphology, the extension of the notochordal canal into the vertebral centrum (blue arrows), and the orientation of the spinal cord–supporting bony processes (pink arrows) in representative genera of lissamphibians (salamanders, frogs and toads, and caecilians).
Figure 6. The ontogenetic pattern of the atlas in the extant Central Asian hynobiid Paradactylodon mustersi shows that the atlantal intercotylar tubercle is formed by the fusion of left and right halves, in sharp contrast to early salamanders, in which the tubercle is composed of dorsal and ventral halves and in most cases remains unfused. Scale bar, 2 mm.
Figure 7. Atlas morphology of three representative extant caecilian genera shows that the inner wall of their neural canal likewise bears spinal cord–supporting bony processes, which extend anteroventrally—indicating that such processes are not unique to anurans and caudates.
A. Typhlonectes natans (UF 149302); B. Ichthyophis bombayensis (UF 76734); C. Caecilia tentaculata (KU 175441). Scale bar, 2 mm.
Since 2019, the research team led by Wu Wenhao at our center has been investigating the Late Cretaceous vertebrate fauna of the Songliao Basin. To date, the team has discovered and published a rich assemblage of Late Cretaceous vertebrate fossils, including dinosaurs, squamates, mammals, and fishes. Among these, the first discoveries in China of Late Cretaceous representatives of several dinosaur groups—including dromaeosaurines, alvarezsaurids, Richardoestesia, and Paronychodon—as well as marsupial mammals, are of great significance for understanding the diversity and evolution of Late Cretaceous vertebrate faunas in East Asia. The present study fills the gap in the fossil record of Late Cretaceous salamanders in East Asia and provides important material for exploring the early history of the Hynobiidae and the evolutionary development of the head–neck joint in salamanders. The findings also lay the groundwork for further understanding the relationships among skeletal development, functional morphology, and ecological adaptation in lissamphibians.
Wu Wenhao (Jilin University), and Jia Jia (IVPP) are co-first authors and co-corresponding authors of the paper. Co-authors include Song Jialin (IVPP), Wang Yuan (IVPP), Gao Keqin (Peking University). This research was supported by the National Key Research and Development Program of China (2025YFF0811700) and the General Program of the National Natural Science Foundation of China (42572018).
Paper link: https://onlinelibrary.wiley.com/doi/10.1002/spp2.70133
