Exposure of the Tiaojishan Formation at Nanshimenzi Village, Qinglong Manchu Autonomous County, Hebei Province, with red arrow pointing to fossiliferous beds
Using Argon–argon dating, Wang and colleagues in 2005 dated part of the Tiaojishan Formation to about 160 million years ago, the beginning of the Oxfordian stage, the first stage of the Upper Jurassic epoch.[2] In 2006, a study by Liu and colleagues used U-Pb zircon dating to conclude that the Tiaojishan Formation correlates with the Daohugou Beds, and the complete chronological range of this shared biota dates to between 168 and 164/152 Ma ago.[3] A subsequent study, published in 2008, refined the age range of the formation further, finding that the lower boundary of the Tiaojishan was formed 165 Ma ago, and the upper boundary somewhere between 156 and 153 Ma ago.[4]
Climate
Based on the plant life present in the Tiaojishan Formation, Wang Yongdong and colleagues determined that the climate in Liaoning during the mid Jurassic would have been subtropical to temperate, warm and humid.[1]
Fauna
Beautifully preserved fossils of dinosaurs, pterosaurs, salamanders, insects, arachnids[5] and other invertebrates, conifers, ginkgoes, cycads, horsetails, and ferns, and even the earliest known gliding mammal (Volaticotherium) have been discovered in these rocks.The tuffaceous composition of some rock layers show that this was a volcanic area, occasionally experiencing heavy ashfalls from eruptions. The landscape then was dominated by mountain streams and deep lakes surrounded by forests of gymnosperm trees.[6]
The forests of the Yanliao biota grew in a humid, warm - temperate climate and were dominated by gymnosperm trees. There were ginkgopsids like Ginkoites, Ginkgo, Baiera, Czekanowskia, and Phoenicopsis. There were also conifers like Pityophyllum, Rhipidiocladus, Elatocladus, Schizolepis, and Podozamites. Also, Lycopsids like Lycopodites and Sellaginellities, horsetails (Sphenopsida) like Equisetum, cycads like Anomozamites, and ferns (Filicopsida) like Todites and Coniopteris.[7]
A cryptobranchoid characterized by its short trunk (only 14 presacrals) and short and wide head, giving a fat body shape, from which the genus name was derived ("Pang" means fat in Chinese).
A wukongopterid named after Charles Darwin. The type species, D. modularis was the first known pterosaur to display features of both long-tailed rhamphorhynchoids and short-tailed pterodactyloids, and was described as a transitional fossil between the two groups. Darwinopterus specimens have also been reported to show several differences between males and females, with the males having distinctive crests on their heads. They are known to have laid their eggs on the ground, and may have also not shown that much for parental care.
An anurognathid pterosaur of uncertain age. Originally reported from the Cretaceous aged Yixian Formation, it may be instead be from the mid-Jurassic Daohugou beds.[16]
A scaphognathinerhamphorhynchid similar to other scaphognathines in its short, blunt skull with a large antorbital fenestra, and widely spaced, vertically oriented teeth (as opposed to the horizontally-oriented teeth of other rhamphorhynchids).
A batrachognathine anurognathid, originally thought to be from the Early Cretaceous, with a wingspan that is about 40 centimeters, making it one of the smallest known pterosaurs. Originally classed as a species of Dendrorhynchoides.
A darwinopteran with a tall crest on its head and an elongated skull 11.8 centimeters (4.6 in) long, a long tail and a wingspan of about 85 centimeters (33 in). It was originally believed to be a rhamphorhynchid. The only known specimen consists of an articulated, nearly complete skeleton with remains of the integument. These included the wing membrane, hair-like pycnofibers, a long version of the vane found at the end of "rhamphorhynchoid" tails, and a head crest with both a low bony base and a large keratin extension.
An anchiornithid at first believed to be a troodont. Given the exquisite preservation of one of the first specimen's fossils, Anchiornis became the first dinosaur species for which almost the entire life coloration could be determined. Most of the body feathers of Anchiornis were gray and black. The crown of head feathers was mainly rufous with a gray base and front, and the face had rufous speckles among predominantly black head feathers. The wing and hind leg feathers were white with black tips. The coverts were gray, contrasting the mainly white main wings. The larger coverts of the wing were also white with gray or black tips, forming rows of darker dots along mid-wing. These took the form of dark stripes or even rows of dots on the outer wing (primary feather coverts) but a more uneven array of speckles on the inner wing (secondary coverts). The shanks of the legs were gray other than the long leg feathers, and the feet and toes were black. It was 13 inches long and weighed only 110 grams (3.9 ounces).
An anchiornithid roughly the size of a modern pheasant, with a length of 20 inches. Its leg bones were similar to those of Archaeopteryx, but overall its anatomy was more primitive.
An anchiornithid known from an adult specimen measuring 400 mm in body length. Its fossilized feathers possess nanostructures which were analyzed and interpreted as melanosomes, showing similarity to organelles that produce a black iridescent color in certain species of extant birds. Other feathers found on the head, chest, and the base of the tail preserve flattened sheets of platelet-like melanosomes very similar in shape to those which create brightly colored iridescent hues in the feathers of modern hummingbirds. However, these structures are seemingly solid and lack air bubbles, and thus are internally more akin to the melanosomes in trumpeters than hummingbirds. Caihong represents the oldest known evidence of platelet-like melanosomes. It is named for the large crest on the lacrimal bone of the skull.[31]
An anchiornithid at first believed to be a troodont, known from a single fossil specimen representing the nearly complete skeleton of a subadult or adult individual. The specimen is very small, measuring about 12 inches long.
A scansoriopterygid known from a well-preserved partial skeleton, measuring 10 inches in length (17.5 inches including the incomplete tail feathers), that includes four long feathers on the tail, composed of a central rachis and vanes. However, unlike in modern-style rectrices, the vanes were not branched into individual filaments but made up of a single ribbon-like sheet. Epidexipteryx also preserved a covering of simpler body feathers, composed of parallel barbs as in more primitive feathered dinosaurs. However, the body feathers of Epidexipteryx are unique in that some appear to arise from a "membranous structure" at the base of each feather. It has been suggested that this may represent a stage in the evolution of the feather. Epidexipteryx and its kin represent the earliest known examples of ornamental feathers in the fossil record.
An anchiornithid that probably measured 1 meter (3.3 feet) or less in length, but since this species is only known from the hind legs, the actual length is difficult to estimate. Apart from having a very birdlike skeletal structure in its legs, Pedopenna was remarkable due to the presence of long pennaceous feathers on the metatarsus (foot). Some other paravians are also known to have these 'hind wings', but those of Pedopenna differ from those of animals like Microraptor. Pedopenna hind wings were smaller and more rounded in shape. The longest feathers were slightly shorter than the metatarsus, at about 55 mm (2.2 in) long. Additionally, the feathers of Pedopenna were symmetrical, unlike the asymmetrical feathers of some other non-avian paravians and birds. Since asymmetrical feathers are typical of animals adapted to flying, it is likely that Pedopenna represents an early stage in the development of these structures. While many of the feather impressions in the fossil are weak, it is clear that each possessed a rachis and barbs, and while the exact number of foot feathers is uncertain, they are more numerous than in the hind-wings of Microraptor. Pedopenna also shows evidence of shorter feathers overlying the long foot feathers, evidence for the presence of coverts as seen in modern birds. Since the feathers show fewer aerodynamic adaptations than the similar hind wings of Microraptor, and appear to be less stiff, suggests that if they did have some kind of aerodynamic function, it was much weaker than in other non-avian paravians and birds.
An anchiornithid with plumulaceous-like feathers. Feather imprints include wispy bundles along the neck, short and symmetrical vaned feathers on the arms, and both fuzz and long pennaceous feathers on its hind limbs (bearing a striking resemblance of the delicate hind limb filaments to the modern Silkie breed of domestic chicken). While its anatomy and integument share features with birds as well as derived dromaeosaurs such as Microraptor, cladistic analysis places the genus within the cluster of feathered non-avian dinosaurs near the origin of avialans. It was unlikely to be a flier.
A heterodontosaur that was initially reported as being from the Early Cretaceous Jehol group. The fossil was collected at a locality transliterated as Linglengta or Linglongta. Lu et al., 2010, reported that these beds were actually part of the Tiaojishan Formation, dating from the Late Jurassic period. Tianyulong has a row of long, filamentous integumentary structures on the back, tail and neck of the specimen, similar to the feathers found in certain theropods (this suggests that all heterodontosaurs may have had these filaments). The holotype is from a subadult individual that probably measured 70 centimeters in length based on the proportions of the related Southern African species Heterodontosaurus.
An anchiornithid originally thought to be either a dromaeosaur or a troodont. It was morphologically similar to Archaeopteryx and was the size of a domestic chicken hen. It was about 60 cm long and weighed an estimated 0.82 kg. Like Archaeopteryx it had long forelimbs. Its femur was longer than its humerus, 84 mm as against 71 mm.
A gliding scansoriopterygid, weighing about 380 grams (0.84 pounds), that, like other scansoriopterygids, possessed an unusual, elongated third finger, that (in the case of Yi) helped to support a membranous gliding plane made of skin. The planes of Yi were also supported by a long, bony strut attached to the wrist. This modified wrist bone and membrane-based plane is unique among all known dinosaurs, and might have resulted in wings similar in appearance to those of bats. This also leads to the hypothesis that the other two genera of scansoriopterygids also had gliding membranes, but this is yet to be proven official.
A shrew-sized, arboreal docodontid that is known to be one of the earliest tree-climbing mammaliaforms.[37] It measured approximately 13 centimeters from head to tail and weighed about 27 grams. Its appearance was similar to a squirrel, with a long snout, curved, horny claws and flexible ankle and wrist joints typical of modern arboreal mammals. The front teeth were spade-like, indicating that Agilodocodon could gnaw tree bark and consume gum or sap.
An arboreal, prehensile-tailed euharamiyidharamiyidan that was the largest known haramiyidan, estimated to have weighed about 354 grams.[38]Arboroharamiya is unlike any modern mammal in having a lower jaw that can move up, down, and backward, but not forward. It has a rodent-like dentition with enlarged incisors and molars and no canines.
A docodontid specialized for a subterranean burrowing lifestyle. The skeletal structure and body proportions are strikingly similar to the golden mole. It was at least 9 centimeters long, exempting the tail, and weighed at least 9 grams, or perhaps 16 grams.
A small, shrew-like therian, possibly a very basal eutherian, weighing around 15–17 grams (0.53–0.60 oz).[40] The discovery of Juramaia provides new insight into the evolution of placental mammals by showing that their lineage diverged from that of the metatheres 35 million years earlier than previously thought, though its identity as a eutherian and its age as the Late Jurassic have been questioned.[41][42]
An eleutherodontid haramiyidan thought to have been a herbivore that lived on the ground, having a similar posture to modern-day armadillos and rock hyraxes.[43]Megaconus is estimated to have weighed about 250 grams (8.8 ounces).
An omnivorous paulchoffatoidmultituberculate that is the oldest so far described in the multituberculates. It strongly resembled a small rodent (like a rat or a chipmunk).[44] It is estimated to have weighed between 65 and 80 grams, about that of an average chipmunk.
A gliding, flying squirrel-like volaticotherianeutriconodont with a specialized gliding membrane. The teeth of Volaticotherium were highly specialized for eating insects, and its limbs were adapted to living in trees. The gliding membrane was insulated by a thick covering of fur, and was supported by the limbs as well as the tail. The discovery of Volaticotherium provided the earliest-known record of a gliding mammal, and provided further evidence of mammalian diversity during the Mesozoic Era.
A whole-plant osmundacean. Preserved stem 50 cm high and 35–41 cm across. Sterile fronds of Cladophlebis-type, fertile fronds of Todites-type with in-situ spores of Osmundacidites-type.[50]
Form genus of sterile fern fronds, typically assigned to Osmundaceae. A whole-plant osmundacean tree-fern with Cladophlebis fronds attached is known from this formation.
C. chengii, C. liaoningensis, C. plumites, C. preosmunda, C. sinica, C. wangii
Beipiao, Liaoning
Numerous specimens
Interrupted ferns. Numerous fossil rhizomes previously assigned to Millerocaulis or Ashicaulis were interpreted to be close relatives and possible precursors of Claytosmunda claytoniana, the only extant representative of the genus.[51]
Fertile fronds of osmundacean ferns that resemble Todea. Known to attach to "Ashicaulis"-type stems with sterile Cladophlebis-type fronds in this formation.
T. williamsonii
Isolated fertile fronds of osmundacean ferns resembling Todea.
Other plants
Cycads, fairly diverse, with 10 species present in 2 genera.
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