Tiaojishan Formation

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 exceptionally preserved fossils, including those of plants, insects and vertebrates. It 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 "Lanqi Formation."^[1] The Tiaojishan Formation forms a key part of the Yanliao Biota assemblage, alongside the Haifanggou Formation.

Tiaojishan Formation
Stratigraphic range: Bathonian-Oxfordian ~165–153 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Exposure of the Tiaojishan Formation at Nanshimenzi Village, Qinglong Manchu Autonomous County, Hebei Province, with red arrow pointing to fossiliferous beds
Type	Geological formation
Underlies	Tuchengzi Formation, Houcheng Formation
Overlies	Haifanggou Formation
Thickness	2,420 m (7,940 ft)
Lithology
Primary	Andesite
Other	Sandstone, shale, tuff, coal
Location
Coordinates	41.3°N 119.2°E / 41.3; 119.2
Approximate paleocoordinates	43.0°N 123.1°E / 43.0; 123.1
Region	Hebei, Inner Mongolia, & Liaoning
Country	China
Extent	Yanshan Belt
Tiaojishan Formation (China) Show map of China Tiaojishan Formation (Liaoning) Show map of Liaoning

Age

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]

Fish

Fish of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Yanliaomyzon	Y. occisor[8]	Liaoning			A lamprey.	Yanliaomyzon

Salamanders

Salamanders of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Beiyanerpeton	B. jianpingensis[9]	Liaoning				Chunerpeton
Chunerpeton	C. tianyiensis
Jeholotriton	J. paradoxus
Liaoxitriton	L. daohugouensis
Pangerpeton	P. sinensis

Pterosaurs

Pterosaurs of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Archaeoistiodactylus	A. linglongtaensis[10]	Liaoning			A monofenestratan known from an incomplete skeleton with a partial skull and lower jaw	Darwinopterus modularis Jeholopterus Kunpengopterus antipollicatus Sinomacrops Wukongopterus
Cascocauda	C. rong[11]	Hebei	Daohugou bed[12]	One specimen	A long-tailed batrachognathine anurognathid known from a complete skeleton with preserved impressions of soft-tissue
Changchengopterus	C. pani[13]	Hebei			A pterodactyliform known only from a single specimen of a young juvenile, measuring 475 millimeters (18.7 in) in wingspan.
Daohugoupterus	D. delicatus[14]	Inner Mongolia		One specimen	Pterosaur known from a partial skeleton with soft tissue impressions
Darwinopterus	D. modularis[15]	Liaoning			A wukongopterid
	D. linglongtaensis
	D. robustodens
	D. camposi[16]	Liaoning		One specimen
Dendrorhynchoides?	D. curvidentatus?			One specimen	An anurognathid; originally reported from the Yixian Formation, later suggested to be from Tiaojishan;[17] other studies dispute this[18]
Douzhanopterus	D. zhengi[19]	Linglongta		One specimen	A non-pterodactyloid monofenestratan
Fenghuangopterus	F. lii[20]	Liaoning			A scaphognathine rhamphorhynchid
Jeholopterus	J. ninchengensis	Inner Mongolia		Several specimens[21][22]	A batrachognathine anurognathid with preserved soft tissue anatomy
Jianchangnathus	J. robustus[23]	Liaoning			A scaphognathine rhamphorhynchid known from a single fossil skeleton
Jianchangopterus	J. zhaoianus[24]	Liaoning			A scaphognathine rhamphorhynchid known from a nearly complete skeleton with the skull preserved
Kunpengopterus	K. sinensis[25]	Liaoning	Daohugou bed	Three specimens	A wukongopterid
	K. antipollicatus[26]	Liaoning		Two nearly complete specimens
Liaodactylus	L. primus[27]	Daxishan (Linglongta)		One specimen	A ctenochasmatid
Luopterus	L. mutoudengensis[17][28]	Hebei		One specimen	A batrachognathine anurognathid; originally classed as a species of Dendrorhynchoides; suggested to have been Early Cretaceous in age
Pterorhynchus	P. wellnhoferi	Inner Mongolia	Daohugou bed	One specimen[21]	A darwinopteran known from a nearly complete skeleton including preserved soft-tissue anatomy
Qinglongopterus	Q. guoi[29]	Liaoning			A rhamphorhynchine rhamphorhynchid known from only one specimen
Sinomacrops	S. bondei[12]	Hebei	Daohugou bed	One specimen	A long-tailed batrachognathine anurognathid known from a relatively complete skull and skeleton with soft tissue patches
Wukongopterus	W. lii	Liaoning	Daohugou bed	One specimen[30]	A wukongopterid

Dinosaurs

Ornithischians

Ornithischians of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Pulaosaurus[31]	P. qinglong	Qinglong		One specimen	The first neornithischian described from the Yanliao Biota; known from a well-preserved, articulated, nearly complete skeleton including soft tissue impressions and gut contents.	Pulaosaurus Tianyulong
Tianyulong	T. confuciusi	Liaoning			A heterodontosaur initially reported as being from the Early Cretaceous Jehol group; preserved with feather-like filaments

Theropods

Theropods of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Anchiornis	A. huxleyi[32]	Liaoning		Several specimens[33]	An anchiornithid at first believed to be a troodontid; analysis of the fossils has enabled scientists to determine what colors the animal may have exhibited in life	Anchiornis Aurornis Caihong Eosinopteryx Epidexipteryx Pedopenna Scansoriopteryx Serikornis Xiaotingia Yi
Aurornis	A. xui	Liaoning		One specimen	An anchiornithid roughly the size of a modern pheasant
Caihong	C. juji	Hebei	Yanliao Biota	One specimen	An anchiornithid known from an adult specimen measuring 400 mm in body length; analysis of the fossils has enabled scientists to determine what colors the animal may have exhibited in life[34]
Eosinopteryx	E. brevipenna	Liaoning		One specimen	An anchiornithid at first believed to be a troodontid, known from a single complete skeleton of a subadult or adult individual
Epidexipteryx	E. hui	Inner Mongolia	Daohugou beds	One specimen	A scansoriopterygid known from a well-preserved partial skeleton, measuring 10 inches in length (17.5 inches including the incomplete tail feathers)
Pedopenna	P. daohugouensis	Inner Mongolia	Daohugou beds	One specimen	An anchiornithid known only from a foot and ankle with soft tissue impressions
Scansoriopteryx	S. heilmanni	Liaoning	Exact provenance of type specimen unknown, most likely from the Daohugou Beds[35]	One or two specimens	A sparrow-sized scansoriopterygid known from one or two juvenile specimens
Serikornis	S. sungei	Liaoning		One specimen[36]	An anchiornithid with plumulaceous-like feathers
Xiaotingia	X. zhengi[37]	Liaoning		One specimen	An anchiornithid originally thought to be either a dromaeosaur or a troodontid
Yi	Y. qi[38]	Hebei	Daohugou beds	One specimen	A gliding scansoriopterygid, weighing about 380 grams (0.84 pounds)

Lizards

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[39]		Inner Mongolia	One specimen	A new lizard with relatively short forelimbs
Unnamed lizard[39]		Inner Mongolia	One specimen	A lizard with long hind limbs and a narrow body

Cynodonts

Cynodonts of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Agilodocodon	A. scansorius	Inner Mongolia	Daohugou bed		A shrew-sized, arboreal docodontid[40]	Agilodocodon Docofossor Juramaia Maiopatagium Megaconus Volaticotherium
Arboroharamiya	A. jenkinsi	Liaoning		One specimen	An arboreal, prehensile-tailed euharamiyid haramiyidan estimated to have weighed about 354 grams[41]
Docofossor	D. brachydactylus	Hebei		One specimen[42]	A docodontid specialized for a subterranean burrowing lifestyle
Juramaia	J. sinensis[43]	Liaoning		One specimen	A small, shrew-like therian which weighed around 15–17 grams (0.53–0.60 oz); it may be a stem-eutherian,[43] but this classification has been questioned by some[44][45]
Maiopatagium	M. furculiferum
Megaconus	M. mammaliaformis	Inner Mongolia	Daohugou bed	One specimen	An eleutherodontid haramiyidan thought to have been a herbivore that lived on the ground[46]
Microdocodon	M. gracilis		Daohugou bed		A tegotheriid docodontan
Qishou	Q. jizantang				Euharamiyida
Rugosodon	R. eurasiaticus	Liaoning	Daxishan site	One specimen	An omnivorous paulchoffatoid multituberculate; one of the oldest-known multituberculates[47] It is estimated to have weighed between 65 and 80 grams, about that of an average chipmunk.
Volaticotherium	V. antiquum	Inner Mongolia	Daohugou bed	One specimen	A gliding, flying squirrel-like volaticotherian eutriconodont with a specialized gliding membrane
Vilevolodon	V. diplomylos				A gliding eleutherodontid haramiyidan
Xianshou	X. linglong, X. songae				A gliding euharamiyidan

Arthropods

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

An indeterminate aeshnoid (insect) species is known from Liaoning.^[32]

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	Images
Ahirmoneura	A. neimengguensis[48]	Inner Mongolia		A tangle-veined fly
Archirhagio	A. striatus[49]			Archisargid flies
	A. zhangi[50]	Inner Mongolia
Archisargus	A. spurivenius[49]			Archisargid flies
	A. strigatus[49]
Calosargus	C. (Calosargus) antiquus[49]			Archisargid flies
	C. (C.) bellus[49]
	C. (C.) daohugouensis[49]
	C. (C.) hani[49]
	C. (C.) tenuicellulatus[49]
	C. (C.) validus[49]
	C. (Pterosargus) sinicus[49]	Inner Mongolia
Darwinula	D. impudica[32]	Liaoning		An ostracod
	D. magna[32]	Liaoning		An ostracod
	D. sarytirmenensis[32]	Liaoning		An ostracod
Daohugocorixa	D. vulcanica[49]			A water boatman
Fuyous	F. gregarious[49]			A mayfly
Eoplectreurys	E. gertschi[51]		1 Specimen	A plectreurid spider
Homocatabrycus	H. liui[52]			A schizophorid flying water beetle
Jurassinemestrinus	J. orientalis[49]	Inner Mongolia		A Nemestrinoid fly
Menopraesagus	M. explanatus[52]			Schizophorid flying water beetles
	M. oxycerus[52]
	M. grammicus[52]
Meoslova	M. daohugouensis[49]			An archisargid fly
Mostovskisargus	M. portentosus[49]	Inner Mongolia		Archisargid flies
	M. signatus[49]	Inner Mongolia
Shantous	S. lacustris[49]			A mayfly
Sinoschizala	S. darani[52]			A schizophorid flying water beetle

Other invertebrates

Genus	Species	Province	Stratigraphic Position	Abundance	Notes
Shaanxiconcha	S. cliovata[32]	Liaoning		A bivalve

Flora

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

Bennettitales

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

Bennettitales of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Anomozamites
Bennetticarpus
Cycadolepis
Jacutiella
Pteriophyllum
Ptilophyllum
Williamsonia
Williamsoniella
Zamiophyllum
Zamites

Ginkgoales

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

Ginkoales of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Ginkgo
Ixostrobus
Phoenicopsis
Sphenobaiera
Solenites

Pinophyta

Conifers, 5 species present in 4 genera.

Pinophytans of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Pityocladus
Pityophyllum
Podizamites
Schizolepis
Yuccites

Pteridophyta

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

Pteridophytans of the Tiaojishan Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Ashicaulis		Beipiao		One specimen	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.[53]
Cladophlebis					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.
Claytosmunda	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.[54]
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.
Todites	T. denticulata				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.

Cycads 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.