Name: Liaoning Province
Age: Early Cretaceous
The preserved fauna and flora is of high diversity and abundance. It represents a terrestrial fauna with a distinctive freshwater component. The unusual preservation has provided evidence for many evolutionary questions, such as the origin and evolution of flight and feathers, the origin of angiosperms (flowering plants) and the origin of placental mammals. The unusual diversity and abundance of individuals also allows studies of population dynamics and community ecology, as well as the ontogeny and development of individual taxa. Most of the major groups are represented in the biota .
Over 1000 invertebrate species have been recovered from the Jehol Biota . The most abundant animals are arthropods, but much of the material remains undescribed. The invertebrate fauna includes insects, spiders, crustaceans, bivalves and gastropods. Fossils of flies with long tubular mouthparts suggest that nectar-producing angiosperms were present at this time, and that there may have been plant-insect associations and coevolution present, even so early in the history of angiosperms. .
Mammals from Jehol include early placental mammals. The Jehol mammals were ground-dwellers or climbers, and all were carnivores or insectivores .
By far the best known components of the Jehol biota are the feathered dinosaurs and primitive birds. They have been intensively studied and have attracted a great deal of public attention. The discovery of small dinosaurs with feathers with feathers has strengthened the dinosaur-bird evolutionary link .
|Sinosauropteryx prima. Redrawn after .|
The first feathered dinosaur to be found was Sinosauropteryx. Its name means “first Chinese dragon feather”. It was a small theropod dinosaur known as a coelurosaur, belonging to the family Compsognathidae. It was covered with delicate, hair-like feathers, but could not fly. These feathers are thought to have first evolved as insulation, and provide evidence that feathers did not evolve for the purpose of flying. It had long legs, short arms, a bony tail and sharp teeth. Its long tail was probably used for balance. It is thought to have eaten lizards, insects and small mammals .
Other feathered dinosaurs found include Caudipteryx, Protarchaeopteryx and Sinornithosaurus.
|Caudipteryx zoui. Redrawn after .|
To date, no theropod dinosaurs have been found with flight feathers. Non-theropod dinosaurs have also been found in the Jehol Biota, including psittacosaurs and ankylosaurs. There have been rumours of bristles in some of the non-theropod dinosaurs .
Some of the oldest known birds are from the Liaoning Province. They had true flight feathers and keeled breastbones, which suggests that they could fly .
Confuciusornis (Confucius bird) was one of the earliest birds to have developed nearly fully modern flight apparatus, and offers new evidence for how a grasping hand evolved into a flying hand.
|Confuciusornis sanctus. Redrawn after .|
Other proto-birds include Sinornis, Liaoxiornis and Yixianornis. The fossils show several stages in the evolution of feathers and flight, and reveal how the arms were transformed into flying wings. The evidence demonstrates that birds evolved from the small, meat-eating theropods .
Many other vertebrates were present in the Jehol Biota. These include two types of frog, long-necked marine reptiles, pterosaurs, fish and turtles. The majority of the fish are small Lycoptera, which are used as index fossils; these have both eyes and gills preserved. Many of the fish had distinctive bony skulls. An unusual feature is that no crocodiles have been found in the Jehol Biota, and it is not known why they were apparently absent .
Many of the fossil plants from the Jehol Biota are new to science. Archaeofructus is a possible candidate for the earliest angiosperm, showing that they had already evolved by the Early Cretaceous. Several new kinds of Gnetales were present; these plants are closely related to the conifers and were dominant. They are of only minor importance today. Six species of horsetails are represented; dormant nodules have been found, which shows that the climate was seasonal. Several kinds of ferns, bryophytes, conifers and gingkoalean plants are also known .
Many of the new plants have no characteristics of modern groups and therefore have uncertain affinities .