Palaeontologists have described a new species of microraptorine theropod from north-western China. Named Jian changmaensis, this small, feathered dinosaur probably glided on four wings. The fossil provides fresh insights into Early Cretaceous ecosystems and extends the known range of the Microraptorinae. The fossil material consists of an articulated partial left pectoral girdle and forelimb. It consists of a complete scapulocoracoid, humerus, radius, and ulna. The specimen number is GSGM-D050.
The fossil comes from the Lower Cretaceous Xiagou Formation of the Changma Basin (Gansu Province). These lake deposits date to the Aptian faunal stage. Researchers have collected more than one hundred bird fossils from this site. However, no non-avian dinosaur body fossils had been described until now. Jian is the first non-avian dinosaur body fossil from the Xiagou Formation of the Changma Basin.
Jian changmaensis life reconstruction. The new microraptorine theropod Jian changmaensis (left) attacks the early bird Gansus yumenensis (right) in what is now the Changma Basin of north-western China approximately 120 million years ago. Picture credit: illustration by Lewis LaRosa, colourised by Jão Canol.
Picture credit: Lewis LaRosa, colourised by Jão Canol
Jian changmaensis from the Xiagou Formation
The location is famous for the relative abundance of aquatic bird fossils. This assemblage is dominated by fossils of the pigeon-sized Gansus yumenensis. Classified as an ornithuran, G. yumenensis is thought to be a closely related to the ancestors of modern birds. Many of the specimens preserved in the fine-grained mudstones show soft tissue structures like feathers and webbing between their toes. This prehistoric bird was probably volant and capable of diving.
Scientists Suspected the Presence of a Predator
Intriguingly, palaeontologists had found examples of crushed bird bones and evidence of regurgitated remains, interpreted as undigestible pellets coughed up by a predator. Scientists speculated that a larger predatory animal must have hunted these ancient birds. However, direct fossil evidence proved elusive. Although far from complete, the limb bones preserve enough anatomical information to identify a new genus and species within the Dromaeosauridae family. Specifically, phylogenetic analysis places Jian changmaensis within the Microraptorinae subfamily. This group contains small dromaeosaurids closely related to Microraptor. Members of this clade are famous for their feathered limbs and possible gliding abilities.
Holotype of Jian changmaensis, (GSGM-D050), an articulated partial left pectoral girdle (scapulocoracoid) and forelimb (humerus, radius, and ulna). Silhouette of generalised microraptorine dromaeosaurid theropod (courtesy Scott Hartman) showing skeletal elements preserved (A). Photograph of specimen as preserved, exposed primarily in dorsomedial (scapulocoracoid), caudodorsal (humerus), and dorsal (radius and ulna) views (B). Interpretive line drawing (C) of B. Photograph of scapulocoracoid and proximal end of humerus in caudodorsal view (D), showing supracoracoid fenestra and other structures. Interpretive line drawing (E) of D. Abbreviations: ac, acromion; bc, bicipital crest; C, coracoid; cr, caudal ridge; dep, dorsal epicondyle; dpc, deltopectoral crest; dr, dorsal ridge; ed, epicondylar depression; fs?, fossa for M. supinator?; H, humerus; hh, humeral head; lp, lateral process; ‘mb’, ‘medial bar’; op, olecranon process; R, radius; S, scapula; scb, scapular blade; scf, supracoracoid fenestra; sta, sternal articulation; U, ulna. Picture credit: Zhou et al.
Picture credit: Zhou et al
A Relative of Microraptor
The researchers surmise that Jian changmaensis probably possessed feathers on both its arms and legs. Therefore, it likely had four wing surfaces. This arrangement may have helped it glide through the forests of Early Cretaceous China. The discovery expands the known fossil record of the Microraptorinae into north-western China. In addition, the partial pectoral girdle indicates that J. changmaensis was much larger than Microraptor. It is one of the largest microraptorines known to science. The fossil material suggests an animal with a wingspan of around a metre to 1.2 metres. This suggests that Jian would have had a wingspan comparable in size to that of the Common Buzzard (Buteo buteo).
The PNSO Microraptor figure, new for 2020 swoops into view.
The picture (above) shows a model of Microraptor. It is the PNSO Gaoyuan model. Microraptor had feathers on its arms and legs, and it has been speculated that it was capable of gliding.
To view the range of PNSO prehistoric animal models in stock: PNSO Age of Dinosaurs Figures.
Similarities with the Famous Jehol Biota
Scientists noted striking similarities between the Changma Basin and the famous Jehol deposits of north-eastern China. Both regions contain microraptorine dinosaurs. Furthermore, both ecosystems included early birds. The Changma deposits contain abundant remains of Gansus yumenensis. Likewise, some Jehol localities are dominated by closely related early birds.
These similarities suggest that the two regions may have shared comparable environments. Such habitats are poorly represented at many other Jehol fossil sites.
The fascinating Jehol Biota: The Jehol Biota.
To read a blog post about a new tiny dromaeosaurid dinosaur from the Jehol fossil sites: New Dromaeosaurid from Liaoning Province (Jehol Biota).
First Non-avian Dinosaur from Changma
The discovery of Jian changmaensis marks an important milestone. It represents the first non-avian dinosaur body fossil reported from the Xiagou Formation. Moreover, the fossil demonstrates that small dromaeosaurids lived alongside numerous early birds. Consequently, scientists now have a better understanding of the biodiversity preserved within the Changma Basin.
Although only part of the skeleton is known, Jian changmaensis provides valuable information. The fossil helps researchers reconstruct the distribution and evolution of microraptorines.
In addition, the discovery highlights the importance of the Changma Basin. Future finds could reveal even more dinosaurs from these remarkable deposits.
Everything Dinosaur acknowledges the assistance of a media release from the Field Museum (Chicago) in the compilation of this article.
The scientific paper: “First non-avian theropod (Dromaeosauridae, Microraptorinae) from the bird-bearing Lower Cretaceous Xiagou Formation of the Changma Basin, Gansu Province, north-western China” by Ling-Qi Zhou, Matthew C. LaManna, Ashley W. Poust, Da-Qing Li, Hai-Lu You and Jingmai K. O’Connor published in the Annals of the Carnegie Museum.
The award-winning Everything Dinosaur website: Dinosaur and Prehistoric Animal Models.
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