A new species of microraptor, named Jianchangmaensis, has been identified from a partial fossil discovered in northwestern China.
The specimen, described in a study published in the Annals of Carnegie Museum, is the first non-avian dinosaur recovered from the Changma Basin in Gansu Province.
Discovery and Context
The fossil was unearthed in the Lower Cretaceous Xiagou Formation near Changma village in the Changma Basin, Gansu Province. It dates to approximately 120 to 124 million years ago. The site is known for yielding over 100 bird fossils, but this is the only non-avian dinosaur specimen found there to date.
The specimen consists of a partial left shoulder and forelimb, which are preserved in three dimensions. It represents one of the largest microraptor specimens known, with an estimated wingspan of approximately 1.2 meters (4 feet).
Classification and Anatomy
The dinosaur belongs to the subfamily Microraptorinae within the family Dromaeosauridae. Microraptors are feathered dinosaurs that are closely related to the lineage that gave rise to birds, but are not classified as birds themselves.
The fossil was identified as a microraptor due to a distinctive feature in the coracoid bone known as the supracoracoid fenestra, a large hole present in all microraptors but rare in other creatures. Like other members of its group, Jianchangmaensis likely had long feathers on both its arms and legs, giving it a four-winged appearance used for gliding.
The species name honors the Changma Basin. "Jian" refers to a one-winged bird in Chinese mythology.
Significance
The discovery extends the known geographic range of Microraptorinae from the Jehol Group in northeastern China to the Changma Basin in Gansu Province, a distance of approximately 2,000 kilometers.
The three-dimensional preservation of the shoulder bones may provide information about the evolution of flight in feathered dinosaurs.
Researchers have noted that clusters of shattered bird bones resembling regurgitated pellets from modern birds of prey have been found at the same fossil bed. Some scientists have suggested that Jianchangmaensis may have been responsible for these remains, as it was a carnivorous dinosaur substantially larger than other known animals from the site.
Scientific Statements
Jingmai O'Connor (Field Museum of Natural History and Institute of Vertebrate Paleontology and Paleoanthropology), senior author of the study, stated that the specimen is one of the largest microraptors found and that it was a carnivore much larger than other specimens recovered from the site.
Matt Lamanna (Carnegie Museum of Natural History), corresponding author, stated that the fossil reveals that non-avian dinosaurs lived in what is now the Changma Basin, an area known for its fossil birds, and provides information on the biological history of the region.
Steve Brusatte (University of Edinburgh), who was not involved in the study, described the fossil as belonging to dinosaurs that were "on the cusp of becoming true birds."
T. Alexander Dececchi (Dakota State University) noted that the fossil expands the geographic range and helps demonstrate the anatomical diversity of the group.
Future Work
Researchers plan to scan the wing fossil to further study the flight or gliding capabilities of microraptors.