Tiaojishan Formation

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Tiaojishan Formation
Stratigraphic range: Bathonian-Oxfordian, 165–156Ma
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

Ornithodirans[edit]

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

Anchiornis

A. huxleyi[17]

Liaoning

Several specimens[18]

A primitive avialan.

Archaeoistiodactylus

A. linglongtaensis[19]

Liaoning

An Istiodactylid pterosaur

Aurornis

A. xui

Liaoning

One specimen

A primitive avialan

Changchengopterus

C. pani[20]

Hebei

A wukongopterid pterosaur

Darwinopterus

D. modularis[21]

Liaoning

Wukongopterid pterosaurs

D. linglongtaensis

D. robustodens

Dendrorhynchoides

D. mutoudengensis[22]

Hebei

One specimen

An anurognathid pterosaur

Eosinopteryx

E. brevipenna

Liaoning

One specimen

A basal paravian

Epidexipteryx

E. hui

Inner Mongolia

Daohugou bed

One specimen

A scansoriopterygid

Fenghuangopterus

F. lii[23]

Liaoning

A rhamphorhynchid pterosaur

Jeholopterus

J. ninchengensis

Inner Mongolia

Several specimens[24][25]

An anurognathid pterosaur

Jianchangnathus

J. robustus[26]

Liaoning

A rhamphorhynchid pterosaur

Jianchangopterus

J. zhaoianus[27]

Liaoning

A rhamphorhynchid pterosaur

Pedopenna

P. daohugouensis

Inner Mongolia

Daohugou bed

One specimen

A primitive avialan

Pterorhynchus

P. wellnhoferi

Inner Mongolia

Daohugou bed

One specimen[24]

A rhamphorhynchid pterosaur

Qinglongopterus

Q. guoi[28]

Liaoning

A rhamphorhynchid pterosaur

Scansoriopteryx

S. heilmanni

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

One or two specimens

A scansoriopterygid

Tianyulong

T. confuciusi

Liaoning

A heterodontosaurid ornithischian

Wukongopterus

W. lii

Liaoning

Daohugou bed

One specimen[29]

A wukongopterid pterosaur

Xiaotingia

X. zhengi[30]

Liaoning

One specimen

A primitive avialan

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[31]

Inner Mongolia

One specimen

A new lizard with relatively short forelimbs

Unnamed lizard[31]

Inner Mongolia

One specimen

A lizard with long hind limbs and a narrow body

Mammals and relatives[edit]

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

Arboroharamiya

A. jenkinsi

Liaoning

One specimen

A haramiyid[32]

Castorocauda

C. lutrasimilis

Inner Mongolia

Daohugou bed

One specimen[33]

An aquatic docodont

Juramaia

J. sinensis[34]

Liaoning

One specimen

A eutherian

Megaconus

M. mammaliaformis

Inner Mongolia

Daohugou bed

One specimen

A haramiyid[2]

Rugosodon

R. eurasiaticus

One specimen

A multituberculate[35]

Volaticotherium

V. antiquum

Inner Mongolia

Daohugou bed

One specimen

A gliding mammal

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[36]

Inner Mongolia

A tangle-veined fly

Archirhagio

A. striatus[37]

Archisargid flies

A. zhangi[38]

Inner Mongolia

Archisargus

A. spurivenius[37]

Archisargid flies

A. strigatus[37]

Calosargus

C. (Calosargus) antiquus[37]

Archisargid flies

C. (C.) bellus[37]

C. (C.) daohugouensis[37]

C. (C.) hani[37]

C. (C.) tenuicellulatus[37]

C. (C.) validus[37]

C. (Pterosargus) sinicus[37]

Inner Mongolia

Daohugocorixa

D. vulcanica[37]

A water boatman

Fuyous

F. gregarious[37]

A mayfly

Eoplectreurys

E. gertschi[39]

1 Specimen

A plectreurid spider

Homocatabrycus

H. liui[40]

A schizophorid flying water beetle

Jurassinemestrinus

J. orientalis[37]

Inner Mongolia

A Nemestrinoid fly

Menopraesagus

M. explanatus[40]

Schizophorid flying water beetles

M. oxycerus[40]

M. grammicus[40]

Meoslova

M. daohugouensis[37]

An archisargid fly

Mostovskisargus

M. portentosus[37]

Inner Mongolia

Archisargid flies

M. signatus[37]

Inner Mongolia

Mongolarachne

M. jurassica[3]

2 Specimens

An orb-weaver spider

Shantous

S. lacustris[37]

A mayfly

Sinoschizala

S. darani[40]

A schizophorid flying water beetle

Other invertebrates[edit]

An indeterminate aeschnoid (insect) species is known from Liaoning.[17]

Genus Species Province Stratigraphic Position Abundance Notes

Darwinula

D. impudica[17]

Liaoning

An ostracod

D. magna[17]

Liaoning

An ostracod

D. sarytirmenensis[17]

Liaoning

An ostracod

Shaanxiconcha

S. cliovata[17]

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]

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