A reconstruction of the newly reported bizarre dinosaur. (Image by Qiu Ji and Xing Lida)

A "bizarre" bird-like dinosaur recently discovered by paleontologists with the CAS Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) has fueled renewed interest in the origin and early evolution of birds. This newly described species, which slightly preceded Archaeopteryx in geological time, surprises its discoverers with an unexpected combination of characteristics from different clades of theropod dinosaurs and some primitive birds. Most strikingly, it also sports two pairs of long primitive feathers on the tail.

The incompletely preserved part of the quartet of ribbon-like feathers measures 20 cm, roughly equaling the trunk length of this pigeon-sized dinosaur. To date, this is the only fossil dinosaur in which such exceptional tail feathers are known. Before this discovery, long, ribbon-like tail feathers had only been documented in such primitive Cretaceous birds as Confuciusornis and Protopteryx. More interestingly, no indication shows that the new bird-like dinosaur was able to fly; in fact it does not possess the pennaceous limb feathers that would be needed for flight, though its forelimbs are about equal in length to its hind limbs as in birds.

What implications might a Jurassic dinosaur have for the origin of birds and feathers, if it has long, ribbon-like tail feathers yet cannot fly? Further evidence is needed to unravel this riddle, but this discovery will undoubtedly lead to new insights into the origin and early evolution of birds, flight and feathers.

Falling in the  taxonomic group known as Avialae, the new species reported in the 23 Oct. issue of Nature represents one of the closest cousins to birds among all dinosaurs. It was unearthed from Mid-Late Jurassic strata in Inner Mongolia, China. The authors suggest that very probably the primary function of the prominent tail feathers might have been ornamentation rather than flight or heat preservation. For this reason the authors give the new animal the genus name "Epidexipteryx," where "Epidexi" is Greek for "display" and "pteryx" Greek for "feather". The name conjures the image of the dinosaur displaying its beautiful feathers.

Long tail feathers are often found in extant birds, and it has been demonstrated that they are used to send visual signals in a wide range of behavior patterns, particularly courtship. According to the authors, the prominent tail feathers of Epidexipteryx might also have been involved in the creature's courtship behavior. It is harder to determine the gender of the specimen, however. Research on extant birds has showed that in some polygynous species, males with long, impressive plumage can attract more mates than short-tailed ones; however, it is not impossible that Epidexipteryx could have been a polyandrous maverick among dinosaurs and their avian descendants. In this case, the specimen might represent a female with showy tail feathers for attracting males.

Either courtship-based interpretation, however, would have one clear implication: as early as the Jurassic Period, at least one dinosaur species had developed obvious secondary sex characteristics that differentiated between the sexes. Unless further evidence can be found to support the possibility that Epidexipteryx is descended from a flying ancestor, and secondarily lost the power of flight, its lack of flight feathers suggests that in basal avialan evolution display feathers appeared prior to airfoil feathers and flight ability.

Estimatedly weighing 164g, the creature has a shortened tail, with much fewer caudal segments than are present in other theropods. Generally a dinosaur has dozens of tail segments, whereas Epidexipteryx has only 16. Such a small number of caudal segments is unknown in most other theropod. Although most birds have even shorter tails, the tail of Epidexipteryx is already shorter than those of some primitive birds like Archaeopteryx and Jeholornis, which have over 20 caudal segments. The strange features of the new specimen suggest that the morphology of maniraptorans, a dinosaur group closely related to birds, could vary in much more complex ways than formerly believed.

The emergence of such a close relative to birds in the Jurassic Period is of importance, in itself, for research on the origin of birds. In his summary the editor of Nature described this discovery as "a trick of the tail feathers" in the evolution of theropod dinosaurs. So far a lot of evidence has been found to support the theory that birds evolved from dinosaurs. The new discovery, made by well-known dinosaur experts Profs. ZHANG Fucheng, ZHOU Zhonghe, XU Xing, WANG Xiaolin and post-doctoral researcher Corwin Sullivan from Canada, further adds to the abundance of evidence, and meanwhile unveils an unexpectedly complex episode in the early evolution from dinosaurs to birds.

Funded by the National Natural Science Foundation of China, the CAS and the Chinese Ministry of Science and Technology, this team has reaped lots of achievements in this field.

The full name of the new specimen is "Epidexipteryx hui  gen. et sp. nov." By designating the species as "hui", the team paid respects to their late colleague, the young paleontologist HU Yaoming. In 1997 Dr. Hu reported in Nature the first mammal specimen from the Jehol Fauna, Zhangheotherium quinquecuspidens. This diligent scholar later published in Nature and Science a series of important discoveries  of mammals from the same important faunal assemblage, while simultaneously battling cancer. He left the mundane world at the height of his scientific career in April 2008, when he was studying at a university in the USA.