Tiaojishan Formation

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Tiaojishan Formation
Stratigraphic range: Bathonian-Oxfordian, 165–156 Ma
Type Geological formation
Sub-units Daohugou bed
Underlies Tuchengzi Formation
Overlies Haifanggou Formation
Thickness 2420 meters
Lithology
Primary Pyroclastic
Location
Region Hebei, Inner Mongolia, & Liaoning
Country  China

The Tiaojishan Formation is a geological formation in Hebei and Liaoning, People's Republic of China, dating to the middle-late Jurassic period (Bathonian-Oxfordian stages). It is known for its fossil plants, and is made up mainly of pyroclastic rock interspersed with basic volcanic and sedimentary rocks. Previously, the Tiaojishan Formation was grouped together with the underlying Haifanggou Formation (also known as the Jiulongshan Formation) as a single "Lanqui Formation."[1] Most researchers now agree that the Daohugou Bed, of formerly controversial dating, is a part of the Tiaojishan formation.[2]

Geology[edit]

The geology of the Daohugou Bed is confusing because it is complex and does not conform; meaning that elements and layers of rock of different ages are mixed up together by folding and erosion and by volcanic activity. Liu et al. (2006) concluded that the rocks that bear the Daohugou Biota also include the Tiaojishan and Lanqi Formations. They demonstrated that the Jiulongshan Formation is older (Middle Jurassic), and that the Tuchengzi Formation is younger (Late Jurassic). However, many other researchers consider the Daohugou to be a part of the Jiulongshan Formation itself.[3]

Fieldwork published in 2006 has also found that the beds are consistent over a large area; from western Liaoning into Ningcheng county of Inner Mongolia (Nei Mongol).[4]

Age[edit]

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.[5] 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.[6] 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 156-153 Ma ago.[7]

Daohugou bed[edit]

The age of the Daohugou bed has been debated, and a number of studies, using different methodologies, have reached conflicting conclusions. Various papers have placed the fossils here as being anywhere from the Middle Jurassic period (169 million years ago) to the Early Cretaceous period (122 ma).[8] One of the first studies on the age of the Daohugou beds, published in 2004 by He et al., found them to be Early Cretaceous, only a few million years older than the overlying Jehol beds of the Yixian Formation.[9] The 2004 study primarily used Argon–argon dating of a tuff within the Daohugou Beds to determine its age.

However, subsequent studies cast doubt on this relatively recent age. In a 2006 study, Gao & Ren criticized He et al. for not including enough specifics and detail in their paper, and also took issue with their radiometric dating of the Daohugou tuff. The tuff, Gao and Ren argued, contains crystals with a variety of diverse radiometric ages, some up to a billion years old, so using dates from only a few of these crystals could not determine the overall age of the deposits. Gao and Ren went on to defend a Middle Jurassic age for the beds based on biostratigraphy (the use of index fossils), and the bed's relationship to a layer that is known to mark the Middle Jurassic-Late Jurassic boundary.[10]

Another study, published in 2006 by Wang et al., argued that the 159-164 million years old Tiaojishan Formation underlies, rather than overlies, the Daohugou Beds. Unlike the earlier study by Gao and Ren, Wang et al. found an overall similarity between the fossil animals found in the Daohugou Beds and those from the Yixian Formation. The authors stated that

"vertebrate fossils such as Liaoxitriton, Jeholopterus and feathered maniraptorans show much resemblance to those of the Yixian Formation. In other words, despite the absence of Lycoptera, a typical fish of the Jehol Biota, the Daohugou vertebrate assemblage is closer to that of the Early Cretaceous Jehol Biota than to any other biota."

Wang et al. concluded that the Daohugou probably represents the earliest evolutionary stages of the Jehol Biota, and that it "belongs to the same cycle of volcanism and sedimentation as the Yixian Formation of the Jehol Group."[4] However, a later study by Ji et al. argued that the key indicator of the Jehol biota are the index fossils Peipiaosteus and Lycoptera. Under this definition, the earliest evolutionary stage of the Jehol Biota is represented by the Huajiying Formation, and the Daohugou Formation is excluded due to the absence of Lycoptera fossils.[11] Later in 2006, Liu et al. published their own study of the age of the Daohugou beds, this time using Zircon Uranium-lead dating on the volcanic rocks overlying and underlying salamander-bearing layers (salamanders are often used as index fossils). Liu et al. found that the beds formed between 164-158 million years ago, in the Middle to Late Jurassic.[12][6] A 2012 study by Gao and Shubin agreed with this assessment, and reported an Argon–argon date of 164 plus or minus 4 million years ago for the Daohugou horizon.[13]

Climate[edit]

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[edit]

Beautifully preserved fossils of dinosaurs, pterosaurs, salamanders, insects, arachnids[14] and other invertebrates, conifers, ginkgoes, cycads, horsetails, and ferns, and even the earliest known gliding mammal (Volaticotherium) and an aquatic protomammal (Castorocauda) have been discovered in these rocks. These organisms were part of the Daohugou Biota, which was the ecosystem of that Jurassic time. 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.[15] Some authors[who?] have concluded that the Daohugou Biota is an early stage of the Jehol Biota, while recent work[citation needed] has demonstrated that the two are distinct.

The forests of the Daohugou 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.[16]

Amphibians[edit]

Amphibians of the Tiaojishan Formation
Genus Species Location Stratigraphic position Abundance Notes

Beiyanerpeton

B. jianpingensis[13]

Liaoning

A salamandroid salamander

Jeholotriton

J. paradoxus

Wang, 2000

Chunerpeton

C. tianyiensis

Gao & Shubin, 2003

Liaoxitriton

L. daohugouensis

Wang, 2004

Pangerpeton

P. sinensis

Wang & Evans, 2006

Pterosaurs[edit]

Pterosaurs of the Tiaojishan Formation
Genus Species Location Stratigraphic position Abundance Notes Images

Archaeoistiodactylus

A. linglongtaensis[17]

Liaoning

An istiodactylid known from an incomplete skeleton with a partial skull and lower jaw.

Changchengopterus

C. pani[18]

Hebei

A monofenestratan known only from a single specimen of a young juvenile, measuring 475 millimeters (18.7 inches) in wingspan.

Daohugoupterus

D. delicatus[19]

Inner Mongolia

One specimen

A relatively basal pterosaur known from a partial skeleton with soft tissue impressions..

Darwinopterus

D. modularis[20]

Liaoning

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. They may have also not shown that much for parental care.

D. linglongtaensis

D. robustodens

Dendrorhynchoides

D. mutoudengensis[21]

Hebei

One specimen

An anurognathid with a wingspan that is about 40 centimeters, making it one of the smallest known pterosaurs.

Fenghuangopterus

F. lii[22]

Liaoning

A scaphognathine rhamphorhynchid 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).

Jeholopterus

J. ninchengensis

Inner Mongolia

Several specimens[23][24]

An anurognathid preserved with pycnofibres and skin remains.

Jianchangnathus

J. robustus[25]

Liaoning

A scaphognathine rhamphorhynchid known from a single fossil skeleton.

Jianchangopterus

J. zhaoianus[26]

Liaoning

A scaphognathine rhamphorhynchid known from a nearly complete skeleton with the skull preserved.

Pterorhynchus

P. wellnhoferi

Inner Mongolia

Daohugou bed

One specimen[23]

A rhamphorhynchid with a tall crest on its head and an elongated skull 11.8 centimeters (4.65 inches) long, a long tail and a wingspan of about 85 centimeters (33.46 inches).

Qinglongopterus

Q. guoi[27]

Liaoning

A rhamphorhynchine rhamphorhynchid known from only one specimen that includes a skeleton with a skull.

Wukongopterus

W. lii

Liaoning

Daohugou bed

One specimen[28]

A wukongopterid unusual for having both an elongate neck and a long tail. Its wingspan is estimated at 730 millimeters (29 inches).

Dinosaurs[edit]

Dinosaurs of the Tiaojishan Formation
Genus Species Location Stratigraphic position Abundance Notes Images

Anchiornis

A. huxleyi[29]

Liaoning

Several specimens[30]

A primitive avialan at first believed to be a troodontid. 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 34 centimeters (13 inches) and weighed only 110 grams (3.9 ounces).

Aurornis

A. xui

Liaoning

One specimen

A primitive avialan that may be the most basal avialan dinosaur known to date, and it is one of the earliest avialans found to date. The fossil evidence for the animal predates that of the Archaeopteryx lithographica, often considered the earliest bird species, by about 10 million years. Aurormis was roughly the size of a modern pheasant, with a length of 50 centimeters (20 inches).

Eosinopteryx

E. brevipenna

Liaoning

One specimen

A basal paravian (probably an avialan) known from a single fossil specimen representing the nearly complete skeleton of a subadult or adult individual. The specimen is very small for a non-avialan dinosaur, measuring about 30 centimeters (12 inches, or 1 foot) long.

Epidexipteryx

E. hui

Inner Mongolia

Daohugou beds

One specimen

A scansoriopterygid known from a well preserved partial skeleton, measuring 25 centimeters (10 inches) in length (44.5 centimeters or 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 represents the earliest known example of ornamental feathers in the fossil record.

Pedopenna

P. daohugouensis

Inner Mongolia

Daohugou beds

One specimen

A primitive avialan, probably measuring 1 meter (3 feet) or less in length, that is possibly older than Archaeopteryx, though the age of the Daohugou Beds is debated.

Scansoriopteryx

S. heilmanni

Liaoning

Exact provenance of type specimen unknown, most likely from the Daohugou Beds[4]

One or two specimens

A sparrow-sized scansoriopterygid known from a juvenile specimen.

Tianyulong

T. confuciusi

Liaoning

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 South African species Heterodontosaurus.

Xiaotingia

X. zhengi[31]

Liaoning

One specimen

A primitive avialan originally thought to be either a dromaeosaur or a troodontid.

Yi

Y. qi[32]

Hebei

Daohugou beds

One specimen

A gliding scansoriopterygid, weighing about 380 grams (0.84 pounds), that, like other scansoriopterygids, possessed an unusual, elongated third finger, that 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.

Lizards[edit]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Lepidosaurs (lizards and relatives) of the Daohugou Beds
Genus Species State Abundance Notes Images

Unnamed lizard[33]

Inner Mongolia

One specimen

A new lizard with relatively short forelimbs

Unnamed lizard[33]

Inner Mongolia

One specimen

A lizard with long hind limbs and a narrow body

Synapsids[edit]

Synapsids of the Tiaojishan Formation
Genus Species Location Stratigraphic position Abundance Notes Images

Agilodocodon

A. scansorius

Inner Mongolia

Daohugou bed

A shrew-sized, arboreal docodont that is known to be the earliest tree-climbing mammaliaform.[34] It measured approximately 13 centimeters from head to tail and weighed about 27 grams.

Arboroharamiya

A. jenkinsi

Liaoning

One specimen

An arboreal, prehensile-tailed euharamiyid haramiyidan that was the largest known haramiyidan, estimated to have weighed about 354 grams.[35]

Castorocauda

C. lutrasimilis

Inner Mongolia

Daohugou bed

One specimen[36]

A semiaquatic docodontid that was highly specialized, with adaptations evolved convergently with those of modern semiaquatic mammals such as beavers, otters, and platypuses. The animal probably weighed about 500-800 grams (1 pound to nearly 2 pounds) and grew to at least 42.5 centimeters (17 inches) in length. This makes it the largest mammaliaform (including true mammals) of the Jurassic (the previous record holder being Sinoconodon).

Docofossor

D. brachydactylus

Hebei

One specimen[37]

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.

Juramaia

J. sinensis[38]

Liaoning

One specimen

A small, shrew-like eutherian with a body length approximately 70-100 millimeters. The discovery of Juramaia provides new insight into the evolution of placental mammals by showing that their lineage diverged from that of the marsupials 35 million years earlier than previously thought. Furthermore, its discovery fills gaps in the fossil record and helps to calibrate modern, DNA-based methods of dating the evolution. Based on climbing adaptations found in the forelimb bones, it has been suggested that the basal stock of eutherians was arboreal.

Megaconus

M. mammaliaformis

Inner Mongolia

Daohugou bed

One specimen

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.[2] Megaconus is estimated to have weighed about 250 grams (8.8 ounces). It probably had an outwardly similar appearance to multituberculates.

Rugosodon

R. eurasiaticus

Liaoning

Daxishan site

One specimen

A paulchoffatiid multituberculate that is the oldest so far described in the multituberculates. It bared a strong resemblance to a small rodent (like a rat or a chipmunk).[39] It is estimated to have weighed between 65-80 grams, about that of an average chipmunk.

Volaticotherium

V. antiquum

Inner Mongolia

Daohugou bed

One specimen

A gliding, flying squirrel-like triconodont 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.

Arthropods[edit]

The following orders are represented in the formation; Ephemeroptera, Odonata, Plecoptera, Blattodea, Orthoptera, Hemiptera, Neuroptera, Coleoptera, Hymenoptera, and Diptera.

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Arthropods of the Daohugou Beds
Genus Species State Abundance Notes

Ahirmoneura

A. neimengguensis[40]

Inner Mongolia

A tangle-veined fly

Archirhagio

A. striatus[41]

Archisargid flies

A. zhangi[42]

Inner Mongolia

Archisargus

A. spurivenius[41]

Archisargid flies

A. strigatus[41]

Calosargus

C. (Calosargus) antiquus[41]

Archisargid flies

C. (C.) bellus[41]

C. (C.) daohugouensis[41]

C. (C.) hani[41]

C. (C.) tenuicellulatus[41]

C. (C.) validus[41]

C. (Pterosargus) sinicus[41]

Inner Mongolia

Daohugocorixa

D. vulcanica[41]

A water boatman

Fuyous

F. gregarious[41]

A mayfly

Eoplectreurys

E. gertschi[43]

1 Specimen

A plectreurid spider

Homocatabrycus

H. liui[44]

A schizophorid flying water beetle

Jurassinemestrinus

J. orientalis[41]

Inner Mongolia

A Nemestrinoid fly

Menopraesagus

M. explanatus[44]

Schizophorid flying water beetles

M. oxycerus[44]

M. grammicus[44]

Meoslova

M. daohugouensis[41]

An archisargid fly

Mostovskisargus

M. portentosus[41]

Inner Mongolia

Archisargid flies

M. signatus[41]

Inner Mongolia

Mongolarachne

M. jurassica[3]

2 Specimens

An orb-weaver spider

Shantous

S. lacustris[41]

A mayfly

Sinoschizala

S. darani[44]

A schizophorid flying water beetle

Other invertebrates[edit]

An indeterminate aeschnoid (insect) species is known from Liaoning.[29]

Genus Species Province Stratigraphic Position Abundance Notes

Darwinula

D. impudica[29]

Liaoning

An ostracod

D. magna[29]

Liaoning

An ostracod

D. sarytirmenensis[29]

Liaoning

An ostracod

Shaanxiconcha

S. cliovata[29]

Liaoning

A bivalve

Flora[edit]

Survey based on Wang et al. 2006 unless otherwise noted.[1]

Bennettitales[edit]

Cycad-like plants, the most abundant plant group in the formation. 27 species in 11 genera.

Plants of the Tiaojishan Formation.
Genus Species Location Stratigraphic position Abundance Notes Images

Anomozamites

Bennetticarpus

Cycadolepis

Jacutiella

Pteriophyllum

Ptilophyllum

Williamsonia

Williamsoniella

Zamiophyllum

Zamites

Ginkgoales[edit]

Prehistoric ginkgo trees, common, with 11 species present in 6 genera.

Plants of the Tiaojishan Formation.
Genus Species Location Stratigraphic position Abundance Notes Images

Ginkgo

Ixostrobus

Phoenicopsis

Sphenobaiera

Solenites

Pinophyta[edit]

Conifers, 5 species present in 4 genera.

Plants of the Tiaojishan Formation.
Genus Species Location Stratigraphic position Abundance Notes Images

Pityocladus

Pityophyllum

Podizamites

Schizolepis

Yuccites

Pteridophyta[edit]

Leptosporangiate ferns, represented by 17 species in 8 genera, are the second most abundant plant type in the formation.

Plants of the Tiaojishan Formation.
Genus Species Location Stratigraphic position Abundance Notes Images

Cladophlebis spp.

Ferns

Coniopteris

Dicksoniaceae Tree ferns.

Dicksonia

D. changeyingziensis

Dicksoniaceae Tree ferns.

D. charielsa

Eboracia

Dicksoniaceae Tree ferns.

Hausmannia

H. shebudaiensis

Uncommon.

A dipterid fern.

Marattia

M. hoerenensis

Uncommon.

A marattiopsid fern.

Raphaelia

R. stricta

A fern.

Toadites

T. denticulata

"Flowering ferns."

T. williamsonii

"Flowering ferns."

Other plants[edit]

Cycads, fairly diverse, with 10 species present in 2 genera.

Plants of the Tiaojishan Formation.
Genus Species Location Stratigraphic position Abundance Notes Images

Ctenis

Cycadales.

Equisetum

Horsetails.

Neocalamites

Horsetails.

Nilssonia

Cycadales.

Hepacitities

H. shebudaiensis

Uncommon.

A bryophyte.

Taeniopteris sp.

Uncommon.

References[edit]

  1. ^ a b c Wang, Y.; Ken, S.; Zhang, W.; Zheng, S. (2006). "Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China". Progress in Natural Science 16 (1): 222–230. doi:10.1080/10020070612330087. 
  2. ^ a b Zhou, C. F.; Wu, S.; Martin, T.; Luo, Z. X. (2013). "A Jurassic mammaliaform and the earliest mammalian evolutionary adaptations". Nature 500 (7461): 163. doi:10.1038/nature12429.  edit
  3. ^ a b Selden, P. A.; Shih, C.; Ren, D. (2011). "A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China". Biology Letters 7 (5): 775–778. doi:10.1098/rsbl.2011.0228. PMC 3169061. PMID 21508021.  edit
  4. ^ a b c Wang, X., Zhou, Z., He, H., Jin, F., Wang, Y., Zhang, J., Wang, Y., Xu, X. & Zhang, F. (2005). "Stratigraphy and age of the Daohugou Bed in Ningcheng, Inner Mongolia." Chinese Science Bulletin, 50(20): 2369-2376.
  5. ^ Xiaolin Wang; Zhonghe Zhou; Huaiyu He; Fan Jin; Yuanqing Wang; Jiangyong Zhang; Yuan Wang; Xing Xu; Fucheng Zhang (2005). "Stratigraphy and age of the Daohugou Bed in Ningcheng, Inner Mongolia". Chinese Science Bulletin 50 (20): 2369–2376. doi:10.1007/BF03183749. 
  6. ^ a b Liu, Y.; Liu, Y.; Ji, S.; Yang, Z. (2006). "U-Pb zircon age for the Daohugou Biota at Ningcheng of Inner Mongolia and comments on related issues". Chinese Science Bulletin 51 (21): 2634–2644. doi:10.1007/s11434-006-2165-2. 
  7. ^ Zhang, H.; Wang, M.; Liu, X. (2008). "Constraints on the upper boundary age of the Tiaojishan Formation volcanic rocks in West Liaoning-North Hebei by LA-ICP-MS dating". Chinese Science Bulletin 53 (22): 3574–3584. doi:10.1007/s11434-008-0287-4. 
  8. ^ Ren, D. et al. (2002). "On the biostratigraphy of the Jurassic fossil beds at Daohugou near Ningcheng, Inner Mongolia." Geol. Bull. China 21, 584-591.
  9. ^ He, H., Wang, X., Zhou, Z., Zhu, R., Jin, F., Wang, F., Ding, X. and Boven, A. (2004). "(^40)Ar/(^39)Ar dating of ignimbrite from Inner Mongolia, northeastern China, indicates a post-Middle Jurassic age for the overlying Daohugou Beds." Geophysical Research Letters 31, L20609.
  10. ^ Gao, K., and Ren, D. (2006). "Radiometric dating of ignimbrite from Inner Mongolia provides no indication of a post-Middle Jurassic age for the Daohugou Beds." Acta Geologica Sinica English Edition, 80(1): 42-45 (February 2006)
  11. ^ Jin, F., Zhang, F.C., Li, Z.H., Zhang, J.Y., Li, C. and Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota." Chinese Science Bulletin, 53(18): 2820-2827.
  12. ^ Liu, Y., Liu, Y., and Zhang, H. (2006). "LA-ICPMS zircon U-Pb dating in the Jurassic Daohugou Beds and correlative strata in Ningcheng of Inner Mongolia." Acta Geologica Sinica (English Edition), 80(5): 733-742.
  13. ^ a b Gao, K. -Q.; Shubin, N. H. (2012). "Late Jurassic salamandroid from western Liaoning, China". Proceedings of the National Academy of Sciences 109 (15): 5767–72. doi:10.1073/pnas.1009828109. PMC 3326464. PMID 22411790.  edit
  14. ^ Notably Mongolarachne jurassica.
  15. ^ Tan, Jingjing, Ren, Dong, Shih, Chungkun. "New Cupedids from the Middle Jurassic of Inner Mongolia, China (Coleoptera: Archostemata)" Annales Zoologici 2006, 56(1):1-6z
  16. ^ Zhang, Kuiyan, Yang, Ding, Ren, Dong. (2006) "The first snipe fly (Diptera: Rhagionidae) from the Middle Jurassic of Inner Mongolia, China" Zootaxa 1134:51-57(2006)z
  17. ^ Lü Junchang and Fucha Xiaohui (2011). "A new pterosaur (Pterosauria) from Middle Jurassic Tiaojishan Formation of western Liaoning, China". Global Geology Z1: 113–118.
  18. ^ Lü, J. (2009). "A new non-pterodactyloid pterosaur from Qinglong County, Hebei Province of China". Acta Geologica Sinica (English Edition) 83 (2): 189–199. doi:10.1111/j.1755-6724.2009.00062.x. 
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