In its time, about 125 million years ago, it must not have seemed remarkable. Jianianhualong tengi was just over three feet long and weighed about as much as a Chihuahua—hardly a match for many of its Cretaceous contemporaries.
But a recent study of this diminutive dinosaur could have an outsized impact on scientists’ understanding of how feathers evolved.
Unearthed in Lioaning, China, the well-preserved fossil represents a new species of troodontid, a family of bird-like dinosaurs. The area in which it was discovered—the Jehol Group, a range of Cretaceous fossils famous for their biodiversity and preservation of stunning detail—has yielded a host of new species in previous years.
What makes Jianianhualong tengi stand out is its asymmetrical feathers, which have long, stiff quills and barbs that are longer on one side than the other.
“It is widely accepted that feather asymmetry is important for [the] origin of bird flight,” e-mails Xu Xing, a palaeontologist at the Chinese Academy of Sciences who co-led this study. “And now we can demonstrate that this feature has a wide distribution outside the bird family.”
TIL: DINOSAURS MAY HAVE DANCED LIKE BIRDS Most researchers believe birds are descendants of a group of dinosaurs that included the Tyrannosaurus rex.
Birds of a Feather
The landmark 1861 discovery of Archaeopteryx, another kind of bird-like dinosaur, was the first clue that dinosaurs might have been more downy than scaly. Subsequent discoveries have reinforced palaeontologists’ understanding that feathers weren’t just for the birds. Feathers offered evolutionarily advantages such as insulation, camouflage, display, and flight support (for some), and were likely a feature of all dinosaurs, even Tyrannosaurus rex.
But not all feathers are created equal. Early ancestors of birds evolved feathers before they were capable of flight, and even the presence of feathers associated with flight—for example, the asymmetrical feathers found on this new species—doesn’t mean that an animal could actually fly.
Could Jianianhualong tengi get off the ground? Probably not.
“It is extremely challenging to accurately reconstruct aerodynamic capabilities in early fossil birds and bird-like dinosaurs because there is a lot of missing data to deal with,” says Michael Pittman, a palaeontologist at the University of Hong Kong and an author of this study, in an e-mail.
The asymmetrical feathers on the new species suggest that it got at least some aerodynamic boost, Pittman says, but in some dinosaur species this may have translated to longer leaps, slowing descents, or other nimble escapes from predators and pounces upon prey.
“However, at this time we don't have enough information to say whether the animal could fly or glide,” Pittman adds.
The holotype, or original example, of this species, is available for public display and scientific study at a museum in Dalian, China. The study authors took careful note of its skeletal features, comparing them to other troodontid specimens and scanning the fossilised remains using a laser-based imaging technique that’s helping palaeontologists see new details in fossils.
The researchers found asymmetrical feathers on the specimen’s tail, but believe it’s likely that the long feathers of the arms and legs were asymmetrical as well.
JURASSIC LANDSCAPE The Jurassic period (199.6 million to 145.5 million years ago) was characterised by a warm, wet climate that gave rise to lush vegetation and abundant life. Many new dinosaurs emerged—in great numbers. Among them were stegosaurs, brachiosaurs, allosaurs, and many others.
ARTWORK BY PUBLIPHOTO/PHOTO RESEARCHERS INC.
ICHTHYOSAUR FOSSIL Four women at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, underscore a 19-foot (5.7-meter), 200-million-year-old ichthyosaur fossil from southern China. Although its name is Greek for "fish lizard," Ichthyosaurus was no fish—it was a reptile that swam the Mesozoic oceans.
PHOTOGRAPH BY O. LOUIS MAZZATENTA
STEGOSAURS WALKING The late Jurassic Stegosaurus, like the pair walking through a North American forest in this illustration, was a slow-moving, plant-eating dinosaur that grew as long as 30 feet (9 meters) and as much as 2 tonnes. Its most impressive feature was a row of large plates and tail spines down the length of its back—some more than three feet (one meter) tall.
ARTWORK BY CHRISTIAN DARKIN/PHOTO RESEARCHERS, INC.
BRACHIOSAUR HERD A herd of brachiosaurs congregates on a forested coast in this artist's depiction. At up to 92 feet (28 meters) and 50 tonnes, these sauropods (large, herbivorous dinosaurs) were much larger than any land animal alive today. Long, lean limbs, high shoulders, and a 30-foot-long (9-meter-long) neck allowed Brachiosaurus to graze from the treetops of North America and parts of Africa, where its fossils have been found.
ARTWORK BY DEA PICTURE LIBRARY
ALLOSAUR AND STEGOSAUR SKELETONS Ghosts of an earlier age, an Allosaurus and a Stegosaurus brace for battle at the Denver Museum in Colorado. Most museum exhibits of dinosaurs do not use actual dinosaur bones, but rather molds and casts. Technicians create fibreglass replicas of bones that are mounted and posed in lifelike positions on metal frames.
PHOTOGRAPH BY JAMES STEINBERG/PHOTO RESEARCHERS, INC.
ALLOSAURUS ARTWORK An Allosaurus tramps through a Mesozoic-era forest in this artist's depiction. Allosaurus was the top predatory dinosaur of the late Jurassic period in North America. Not a particularly fast runner, it likely ambushed unsuspecting prey as it passed by.
ARTWORK BY CHRIS BUTLER/PHOTO RESEARCHERS, INC.
DINOSAUR CLAWS A dig in Dry Mesa, Colorado, revealed these Jurassic jewels: claws from a creature now extinct. All theropods (bipedal dinosaurs that included T. rex and Velociraptor) possessed curved, hooklike claws on their hands and feet, similar to today's birds of prey. Each claw ended with a sharp point ideally suited for digging into the flesh of prey. When worn down, bony claws developed a sharp edge ideal for cutting and slashing.
PHOTOGRAPH BY W.A. ROGERS
DINOSAUR EGGSPaleontologists in China's Henan Basin discovered this nest of fossilised eggs laid by the Jurassic duck-billed herbivore Hadrosaurus. Current evidence suggests all dinosaurs laid eggs of a wide variety of shapes and sizes—from 8 centimetres to 53 centimetres), round or elliptical. Dinosaur eggs were perforated with tiny holes, which allowed life-giving oxygen to enter.
PHOTOGRAPH BY SINCLAIR STAMMERS/SCIENCE PHOTO LIBRARY
CAPITOL REEF NATIONAL PARKSandstone monoliths, dubbed the Temple of the Sun and the Temple of the Moon, tower over the desert flats of Utah's Capitol Reef National Park. These formations were sculpted from sandstone deposited here in the Jurassic period about 160 million years ago.
PHOTOGRAPH BY TAYLOR S. KENNEDY
MESOZOIC MOGOTESDomelike mogotes in Valle de Viñales National Park, Cuba, emerge from a blanket of fog. These geologic formations date to the Mesozoic era, when layers of sedimentary limestone accumulated under water. Over time, acidic chemicals, along with wind and water erosion, molded these limestone remnants into mogotes.
PHOTOGRAPH BY STEVE WINTER
TUATARA REPTILEClinging to life on an offshore crag, a tuatara looks little different from his Jurassic relatives. Today, like many species, this living fossil carries out a threatened existence in New Zealand.
PHOTOGRAPH BY FRANS LANTING
All in the Family
Finding asymmetrical feathers doesn’t just reveal a new bit of flight history; it also sheds new light on the relationship between bird-like dinosaurs and the first birds.
The newly found species is part of a group called troodontids, which in turn is part of a bigger group that included all birds, living and extinct. The new species’ skull and legs are more similar to later species of troodontids, but its arms and pelvis are more similar to early species—a discovery that suggests some features evolved faster than others.
It’s not the mere presence of asymmetrical feathers that make Jianianhualong remarkable—the famous Archaeoptyerx and the four-winged Microraptor, which belong to other branches of the parent group of troodontids and birds, also have asymmetrical feathers.
But finding asymmetrical feathers in a species that holds Jianianhualong’s unique place in the phylogenetic tree suggests that such feathers might be present in the common ancestor of both birds and troodontids—placing this link further back in the tree than previously thought, to about 160 million years ago.
Ryan Carney, a palaeontologist and National Geographic grantee who was not involved with the study, points out that incorporating feather shape into studies of evolutionary relationships is a critical step, often passed over.
“Knowing that the closest common ancestor of birds had asymmetrical feathers? is extremely exciting,” says Pittman.
The scientists hope to find more feathered species, and to take a second look at known species, to understand how asymmetrical feathers evolved—and whether or not this evolution had its roots in flight.
Header Image: An illustrated life reconstruction of Jianianhualong tengi shows off its asymmetrical feathers. PHOTOGRAPH COURTESY JULIUS T. CSOTONYI AND XU, CURRIE, PITTMAN ET AL.