Early Cretaceous
Liaoning China
Liaoning now considered by most experts to date from the Early
Cretaceous. At that time the region was occupied by a shallow, warm lake with abundant fish and bird life.
The lake itself lay in a fault basin flanked by volcanoes, and it is this particular feature that makes the area
so important. Sporadic volcanic eruptions killed large numbers of animals and buried the remains rapidly
before significant decomposition could take place. These specialized conditions have resulted in better
preservation of soft tissue than is found virtually anywhere else, including the famous Solnhofen deposits
in Germany that preserved the Archaeopteryx feather. Dragonfly wings, feathers and fur are all preserved,
and coupled with an enormous number and type of fossilized animals, it is not surprising that the site is
viewed as one of the most exciting and promising yet discovered.
A rich fauna of insects, molluscs, crustaceans, fish (more than 10,000 specimens of 1 species of freshwater
fish, Lycoptera), mammals and birds (including hundreds of skeletons of Confuciusornis) have been recovered, but, at least in recent years, these have to some extent been surpassed by the dinosaurs.
Following the discovery of the controversial and still hotly debated “feathered dinosaur” Sinosauropteryx in 1992, the region has yielded Protarchaeopteryx, Caudipteryx (both now considered dinosaurs rather
than primitive birds as originally suggested), the therizinosaurid Beipiaosaurus and the dromaeosaurid Sinornithosaurus. All of these dinosaurs exhibit the remains of integumentary fibres that are either
definitely feathers (Protarchaeopteryx and Caudipteryx) or more arguably some sort of proto-feather. Feathers clearly did not evolve
primarily for flight, and may have developed for insulation, display, or even as a metabolic clearance
system for excess sulphur), it is generally considered that the discovery of a genuine feathered dinosaur
would be the definitive proof of the dinosaurian origin of birds.
Thus the announcement by Chinese paleontologists that they had discovered just such a beast was met with
claim and counter-claim. Sinosauropteryx, a basal coelurosaur related to Compsognathus, shows evidence
of some type of integumentary structure, but after lengthy and often heated debate, it is still not clear
exactly what these structures might be. They are clearly not modern feathers, and almost as clearly not a
collagen frill as some have proposed. Whether they are some sort of proto-feather remains to be seen.
While the jury may still be out on the integument of Sinosauropteryx, for three more Chinese finds from
the same area there is no doubt at all that they are feathered. Protarchaeopteryx and Caudipteryx were first
announced as basal birds, largely on the basis of their feathers. However, several investigators have since
demonstrated by cladistic analysis that both are theropods - Caudipteryx is an oviraptorosaur andProtarchaeopteryx a maniraptoran. Finally, a feathered therizinosaurid, Beipiaosaurus, was
discovered, as well as the dromaeosaurid Sinornithosaurus and several other similar specimens. Despite
counter-claims that these are simply flightless birds, most seem to accept that feathers arose within the
theropod lineage somewhere, the remaining question being just how far back were they represent
updated 093016
Microraptor zhaoianus (Small robber) is the name given to fossils which includes the dromaeosaurid rear half of the infamous chimera Archaeoraptor. It is the first dinosaur that is smaller than Archaeopteryx. Fuzz-like remains from the pelvic area are similar to that of Beipiaosaurus and Sinornithosaurus but with a central rachis. Microraptor gui the second species show complete covering of 2 types of feathers proto-feathers and flight feathers. It may have been a 4-winged glider. The legs of the two-pound creature could have been held below the body in flight, creating two staggered wing sections, the upper one slightly ahead of the lower one. One other flying dinosaur, Pedopenna, also had feathers on its legs and modern raptors such as falcons have short feathers on their upper legs which reduce air resistance as they fly.
Beipiaosaurus
(Lizard from Beipiao) is yet another of the exciting new finds from the
Liaoning area of China. The discoverers believe that integumentary
filaments up to 70 mm (2.75 in) in length similar to those of Sinosauropteryx represent proto-feathers and suggest that such structures may have been broadly distributed among non-avian theropods. Beipiaosaurus differs from other therizinosaurs in having a larger
skull, and morphological differences in the teeth, hand, pelvis and feet.
Caudipteryx (Tail
feather) is characterized by paired feathers on either side of the end
of the tail, long feathers on its arms and evidence that its entire
body may have been covered with feathers of some sort, including
down-like covering. Feathers are symmetrical, with shorter arms and the
long legs indicate that it probably could not fly and was a ground
dwelling runner.
Dilong
(Emperor Dragon) is a small, basal tyrannosauroid with relatively long
arms and three-fingered hands. Although its skull shows many
characteristics of tyrannosaurids, its postcranial skeleton is more
like a coelurosaurian. It is the earliest known definite
tyrannosauroid, and the integumentary structures found associated with
some tail bones resemble those of Sinornithosaurus and other Liaoning coelurosaurs and represent the first evidence of such “feather-like” features in tyrannosaurs.
Yutyrannus huali, a medium size tyrannosauroid that is the largest known feathered dinosaur and the apex predator in Yixian.
Copyright © 2012 All Rights Reserved