Using fossil remains from northwestern China, paleontologists describe a new, plant-eating dinosaur named Yongjinglong datangi.
The species roamed during the Early Cretaceous period, more than 100 million years ago. This sauropod belonged to a group known as Titanosauria, members of which were among the largest living creatures to ever walk the earth.
At roughly 50-60 feet long, the Yongjinglong individual discovered was a medium-sized Titanosaur. Anatomical evidence, however, points to it being a juvenile; adults may have been larger.
The find, reported in the journal PLOS ONE, helps clarify relationships among several sauropod species that have been found in the last few decades in China and elsewhere. Its features suggest that Yongjinglong is among the most derived, or evolutionarily advanced, of the Titanosaurs yet discovered from Asia.
Doctoral student Liguo Li and professor Peter Dodson, both of the University of Pennsylvania School of Veterinary Medicine’s department of animal biology and the School of Arts and Sciences’ department of Earth and environmental science, led the work.
This latest discovery was made in the southeastern Lanzhou-Minhe Basin of China’s Gansu Province, about an hour’s drive from the province’s capital, Lanzhou. Two other Titanosaurs from the same period, Huanghetitan liujiaxiaensis and Daxiatitan binglingi, were discovered within the last decade in a valley one kilometer from the Yongjinglong fossils.
Shoulder blade hints
During a trip to Gansu, Liguo Li was invited to study the remains, which had been in storage since being unearthed in 2008. They consisted of three teeth, eight vertebrae, the left shoulder blade, and the right radius and ulna.
The anatomical features of the bones bear some resemblance to another Titanosaur that had been discovered by paleontologists in China in 1929, named Euhelopus zdanskyi. But the team was able to identify a number of unique characteristics.
“The shoulder blade was very long, nearly two meters, with sides that were nearly parallel, unlike many other Titanosaurs whose scapulae bow outward,” Li says.
The scapula was so long, indeed, that it did not appear to fit in the animal’s body cavity if placed in a horizontal or vertical orientation, as is the case with other dinosaurs. Instead, Li and colleagues suggest the bone must have been oriented at an angle of 50 degrees from the horizontal.
In addition, an unfused portion of the shoulder blade indicated to the researchers that the animal under investigation was a juvenile or subadult.
“The scapula and coracoid aren’t fused here,” Li says. “It is open, leaving potential for growth.”
Thus, a full-grown adult might be larger than this 50-60 foot long individual. Future finds may help elucidate just how much larger, the researchers note.
The ulna and radius were well preserved, enough so that the researchers could identify grooves and ridges they believe correspond with the locations of muscle attachments in the dinosaur’s leg.
The researchers were also able to draw evidence about the dinosaur’s relationship to other species from the vertebrae, one of which was from the neck and the other seven from the trunk. Notably, the vertebrae had large cavities in the interior that the team believes provided space for air sacs in the dinosaur’s body.
“These spaces are unusually large in this species,” Dodson says. “It’s believed that dinosaurs, like birds, had air sacs in their trunk, abdominal cavity, and neck as a way of lightening the body.”
In addition, the longest tooth they found was nearly six inches long. Another shorter tooth contained unique characteristics, including two “buttresses,” or bony ridges, on the internal side, while Euhelopus had only one buttress on its teeth.
Did sauropods rule?
To gain a sense of where Yongjinglong sits on the family tree of sauropods, the researchers were able to compare its characteristics with specimens from elsewhere in China, as well as from Africa, South America, and the US.
“We used standard paleontological techniques to compare it with phylogenies based on other specimens,” Dodson says. “It is definitely much more derived than Euhelopus and shows close similarities to derived species from South America.”
Not only does the discovery point to the fact that Titanosaurs encompass a diverse group of dinosaurs, but it also supports the growing consensus that sauropods were a dominant group in the Early Cretaceous—a view that US specimens alone could not confirm.
“Based on US fossils, it was once thought that sauropods dominated herbivorous dinosaur fauna during the Jurassic but became almost extinct during the Cretaceous,” Dodson says. “We now realize that, in other parts of the world, particularly in South America and Asia, sauropod dinosaurs continued to flourish in the Cretaceous, so the thought that they were minor components is no longer a tenable view.”
Dodson and Li worked with Hailu You, a former student of Dodson’s, who now works at the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology, and Daqing Li of the Gansu Geological Museum in Lanzhou, China.
Funding for the research came from the National Natural Science Foundation of China, the Hundred Talents Project of the Chinese Academy of Sciences, the Gansu Bureau of Geology and Mineral Resources, and the National Science Foundation.
Source: University of Pennsylvania