Paleobiota of the Yixian Formation
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The Yixian Formation (simplified Chinese: 义县组; traditional Chinese: 義縣組; pinyin: Yìxiàn zǔ) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans about 1.6 million years during the early Cretaceous period (Barremian-Aptian stage). It is known for its fossils, listed below.
The Yixian Formation is divided into the following subunits: (ages from Zhong et al., 2021[1] unless otherwise noted)
- Upper Yixian (124.1 Ma) ("Jingangshan Bed") ("Dawangzhangzi Bed")
- Upper Lava Unit
- Jianshangou Unit (125.46 Ma)
- Lower Lava Unit
- Lujiatun Unit (125.76–125.68 Ma)
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
D. dongi |
Beipiao | Jianshangou Bed |
Partial postcrania[2] |
A basal titanosauriform |
 | |
|
cf. Euhelopus |
cf. E. sp. |
Lujiatun Bed |
A basal titanosauriform | |||
|
L. sinensis |
Nearly complete skeleton[5] |
A basal titanosauriform | ||||
| Ruixinia | R. zhangi | Beipiao | A partial articulated skeleton[6] | A somphospondylan titanosauriform | ||
|
Sauropoda spp. |
Lujiatun & Jianshangou Beds |
One or more species of sauropods, possibly titanosaurs, have been recovered from the Yixian Formation, though most remain undescribed[3] | ||||
Ornithischians
The dinosaurs listed below were compiled in a survey by Xu and Norell in 2006, unless otherwise noted.[7]
Ankylosaurs
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
L. paradoxus |
Yixian |
Dawangzhangzi Bed |
"Partial skull [and] skeleton."[8] |
A small ankylosaur |  |
Ceratopsians
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
L. yanzigouensis |
Beipiao |
Lujiatun Bed |
"[Two] nearly complete skulls, juvenile to adult."[9] |
  | ||
|
Beipiao |
Lujiatun & Jianshangou Beds |
Thousands of specimens in the Lujiatun Bed, somewhat less common in the Jianshangou Bed |
A ceratopsian |
Ornithopods
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
B. yixianensis |
Jianshangou Bed |
A nearly complete skeleton. |
     | |||
| Changmiania[10] | C. liaoningensis | Lujiatun Bed | Two nearly complete skeletons | A basal ornithopod that may have dug burrows | ||
|
H. dongi |
Jianshangou Unit |
Nearly complete skeleton with preserved integument |
A hadrosauroid ornithopod | |||
|
J. shangyuanensis |
Lujiatun Bed |
"Skull with associated vertebrae and hindlimb, skull with cervical vertebrae."[12] |
An ornithopod | |||
|
J. yangi |
Yixian |
Dawangzhangzi Bed |
"Nearly complete skull and skeleton."[13] |
An ornithopod | ||
Theropods
The dinosaurs listed below were compiled in a survey by Xu and Norell in 2006, unless otherwise noted.[7]
Avialans
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
| Abitusavis[14] | A. lii | Ningcheng | "Nearly complete skeleton."[14] |         | ||
|
A. spathula |
Dawangzhangzi Bed |
An early, advanced short-tailed bird (ornithuran)[15] | ||||
|
C. hengdaoziensis[16] |
Jianshangou Bed |
"Nearly complete skeleton."[16] |
||||
|
C. chuonzhous |
Junior synonym of Confuciusornis sanctus[17] | |||||
|
C. dui[18] |
Jianshangou Bed |
"[Two] skeletons."[18] |
||||
|
C. feducciai[19] |
Jianshangou Bed |
|||||
|
C. sanctus[18] |
Jianshangou and Dawangzhangzi Beds |
"Hundreds of complete skeletons."[18] |
A primitive short-tailed bird (pygostylian), also present in the Jiufotang Formation | |||
|
C. suniae |
Junior synonym of Confuciusornis sanctus[17] | |||||
|
D. liweii |
Dawangzhangzi Bed |
|||||
|
E. buhleri |
Jianshangou Bed |
"Nearly complete skeleton."[21] |
||||
|
E. edentulata |
Dawangzhangzi Bed |
"Nearly complete skeleton with skull"[22] |
An ornithuromorph | |||
|
I. huchzermeyeri |
An ornithuromorph; previously regarded as Yixian, horizon reassigned to the Jiufotang Formation by Ju et al., 2021[23] | |||||
|
J. yixianensis |
Jianshangou Bed |
A pygostylian, a junior synonym of Confuciusornis sanctus[24] | ||||
|
J. zhangjiyingia |
Jianshangou Bed |
Junior synonym of C. sanctus | ||||
|
J. orientalis |
Jianshangou Bed |
A basal avialan, also present in the Jiufotang Formation[25] | ||||
|
H. longicresta |
Jianshangou and Dawangzhangzi Beds[26] |
Four specimens[26] |
An ornithuromorph[27] | |||
|
J. luahera |
Previously regarded as Yixian, horizon reassigned to the Huajiying Formation by Jin et al., 2008.[28] | |||||
|
L. longidigitris |
Lujiatun Bed |
"Partial skeleton."[29] |
An enantiornithine.[30] | |||
|
L. delicatus |
Dawangzhangzi Bed |
Considered a nomen dubium because the name is based on remains of a hatchling entantiornithine and cannot be confidently matched with the adult form.[31] | ||||
|
L. parvus |
Dawangzhangzi Bed |
Junior objective synonym of Liaoxiornis delicatus, a nomen dubium.[31] | ||||
|
L. houi |
Dawangzhangzi Bed |
An ornithuromorph[27] | ||||
|
L. hani |
bed unknown |
An enantiornithine | ||||
|
P. fengningensis |
Previously regarded as Yixian, horizon reassigned to the Huajiying Formation by Jin et al., 2008.[28] | |||||
|
M. parvus |
Partial skeleton.[32] |
An immature female enantiornithine preserved with medullary bone tissue.[32] | ||||
| Sapeornis[33] | S. chaoyangensis | Nearly complete skeleton.[33] | A subadult omnivoropterygid with preserved feathers.[33] | |||
|
S. cooperorum |
Dawangzhangzi Bed |
An enantiornithine.[34] | ||||
|
V. hebeiensis |
Previously regarded as Yixian, horizon reassigned to the Huajiying Formation by Jin et al., 2008.[28] | |||||
| Yixianosaurus | Y. longimanus | Dawangzhangzi Bed | An anchiornithid | |||
|
Z. haoae |
Dawangzhangzi Bed |
A primitive avialan with a short but non-pygostylian tail[35] |
Compsognathids
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
| Huadanosaurus[36] | H. sinensis | Dawangzhangzi Bed | A nearly complete specimen missing the feet and end of the tail | A compsognathid |     | |
|
H. orientalis |
Beipiao |
Jianshangou Bed |
A compsognathid | |||
|
S. gigas |
Beipiao |
Jianshangou Bed |
A large compsognathid | |||
| Sinosauropteryx | S. lingyuanensis[36] | Dawangzhangzi Bed | A nearly complete specimen | A compsognathid | ||
|
S. prima |
Beipiao & Lingyuan |
Jianshangou & Dawangzhangzi Beds |
A compsognathid. The first non-avian dinosaur found with feather impressions. | |||
|
S.? sp. |
Beipiao |
Jianshangou Bed |
One specimen (GMV 2124) with partial skull, postcrania, and preserved feathers |
An unnamed coelurosaur originally described as a specimen of Sinosauropteryx, later suggested to be a new genus and species,[39] probably a tyrannosauroid.[36] |
Dromaeosaurs
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
C. yangi |
Jianchang |
A complete articulated specimen with extensive feathering.[40] |
      | |||
|
G. lujiatunensis |
Beipiao |
Lujiatun Bed |
An incomplete specimen. |
A dromaeosaurid | ||
|
S. haoiana |
Yixian |
Dawangzhangzi Bed |
Might be a junior synonym of Sinornithosaurus millenii. | |||
|
S. millenii |
Beipiao |
Jianshangou Bed |
Three specimens with skulls and postcrania, two with preserved feathers.[41] Feathered integument is also preserved.[41][42] |
A dromaeosaurid, the first ever found with feather impressions. | ||
|
T. ostromi |
Lingyuan |
Dawangzhangzi Bed |
A dromaeosaurid | |||
|
Z. suni |
Jianchang |
One nearly complete skeleton with preserved feathers, including long tail feathers and large wing feathers. |
A dromaeosaurid | |||
|
Z. yangi |
Lingyuan |
A partial skeleton includes an arm, legs, vertebrae, ribs, and most of the tail.[44] |
A microraptorian dromaeosaurid with very long legs.[44] | |||
|
Unnamed dromaeosaurid |
Specimen NGMC 91 |
Lingyuan |
Dawangzhangzi Bed |
Complete specimen with feather imprints |
A juvenile dromaeosaurid that may be a specimen of Sinornithosaurus millenii.[45][46] Informally nicknamed "Dave". |
Ornithomimosaurs
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
H. qingyi |
Beipiao |
Lujiatun |
A primitive ornithomimosaur[47] |
 | ||
|
S. orientalis |
Beipiao |
Lujiatun Bed |
"Articulated skull and incomplete skeleton."[48] |
A primitive ornithomimosaur |
Oviraptorosaurs
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
C. dongi |
Beipiao |
Jianshangou Bed |
"[One] partial postcranium with feather imprints."[49] |
 .png)  | ||
|
C. zoui |
Beipiao |
Jianshangou Bed |
Common, only over a small region | |||
|
C. sp.[50] |
||||||
|
I. gauthieri |
Beipiao |
Lujiatun Bed |
"[One] skull [and a] partial cervical."[49] |
An oviraptorosaur | ||
|
N. wangi |
Complete skeleton with feather impressions.[51] |
An oviraptorosaur | ||||
|
P. robusta |
Beipiao |
Jianshangou Bed |
"Nearly complete skull and skeleton, at least [two] individuals."[52] |
A possible relative of Incisivosaurus | ||
|
S. yixianensis |
Two specimens |
An oviraptorosaur, also present in the Jiufotang Formation[53] | ||||
|
X. ganqi |
Liaoning |
Dakangpu Bed |
One nearly complete specimen (IVPP V13390), minus the head |
Therizinosaurs
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
B. inexpectus |
Jianshangou Bed |
"Incomplete skeleton with integument."[55] |
  | |||
| Jianchangosaurus | J. yixianensis | Jianchang | A nearly complete juvenile specimen with feather impressions.[56] | A therizinosaur |
Troodontids
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
| Daliansaurus | D. liaoningensis | Beipiao | Lujiatun Bed | A very complete specimen.[57] | A troodontid |     .png)  |
|
J. tengi |
Beipiao |
Dawangzhangzi Bed |
A very complete specimen with feather impressions.[58] |
A troodontid | ||
| Liaoningvenator | L. curriei | Beipiao | A very complete specimen. | A troodontid | ||
|
M. long |
Beipiao |
Lujiatun Bed |
A small troodontid fossilized in a sleeping position | |||
|
S. changii |
Beipiao |
Lujiatun Bed |
Three specimens with partial skulls and postcrania.[59][60] Hundreds of additional specimens known but undescribed. |
A troodontid | ||
|
S. magnodens |
Beipiao |
Lujiatun Bed |
A troodontid | |||
|
Undescribed deinonychosaur/possible troodontid |
Dawangzhangzi Bed |
One specimen with feather imprints |
A possible troodontid.[61] | |||
|
Undescribed troodontid |
Specimen CAGS-IG01-004 |
Lujiatun Bed |
Skull and partial skeleton |
A troodontid similar to Mei.[62] |
Tyrannosaurs and other theropods
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
D. paradoxus |
Beipiao |
Lujiatun & Jianshangou Bed |
Rare |
  | ||
|
lower Jianshangou Bed |
Footprints belonging to the Grallator form taxon, belonging to a small theropod. Of known Yixian theropods, the footprints most closely match Caudipteryx.[63] | |||||
|
R. kriegsteini |
A tyrannosaurid, probably from higher Mongolian strata. | |||||
|
S. heilmanni |
Initially reported from the Dawangzhangzi Bed, probably from the Daohugou Beds instead.[64] | |||||
|
Y. huali |
Unknown |
Three nearly complete skeletons of various ages |
A large tyrannosauroid[65] | |||
|
Unnamed theropod |
Not yet described |
Lujiatun Bed |
Partial post-cranial skeleton[66] |
A possible allosauroid[67] | ||
Pterosaurs
The pterosaurs listed below were compiled in a survey by Wang and Zhou in 2006, unless otherwise noted.[68]
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
B. chenianus |
Jianshangou Bed |
A ctenochasmatid |
     | |||
|
B. cuiae |
Jianshangou Bed |
A boreopterid | ||||
|
C. grabaui |
Dawangzhangzi Bed |
A ctenochasmatid | ||||
|
D. curvidentatus |
An anurognathid | |||||
|
E. prolatus |
Jianshangou Bed[71] |
A ctenochasmatid | ||||
| Eopteranodon | E. lii[72] | Beipiao | A tapejarid | |||
| E. yixianensis[73] | Beipiao | Jianshangou Bed | A tapejarid | |||
|
E. yangi |
Jianshangou Bed |
A ctenochasmatid | ||||
|
G. changae[71] |
Jianshangou Bed[71] |
A ctenochasmatid | ||||
|
G. jingangshanensis |
Jianshangou Bed |
A ctenochasmatid | ||||
| Haopterus |
H. gracilis |
Jianshangou Bed |
An ornithocheirid | |||
| Luchibang[75][76] | L. xingzhe | One partial skull | An istiodactylid | |||
|
M. zhuiana |
Lujiatun bed? |
A ctenochasmatid | ||||
|
N. liuae |
Jianshangou or Dawangzhangzi bed |
A pterodactyloid[77] | ||||
| Nurhachius | N. sp. | Jingangshan Member[78] | An incomplete specimen[78] | An istiodactylid | ||
|
P. qiui |
Jianshangou Bed |
A ctenochasmatid[71] | ||||
| Yixianopterus | Y. jingangshanensis | An istiodactyliform | ||||
|
Z. longirostris |
Jianshangou Bed |
A boreopterid.[79] May be adult form of Boreopterus.[80] | ||||
Misc. reptiles
Choristoderans
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
H. lingyuanensis |
Dawangzhangzi Bed |
  | ||||
|
H. baitaigouensis |
Jingangshan Bed |
Thousands of specimens |
||||
|
M. splendens |
Dawangzhangzi Bed |
|||||
|
S. lingyuanensis |
Dawangzhangzi Bed |
Junior synonym of Hyphalosaurus lingyuanensis | ||||
Lizards
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
D. longidigitus |
Jianshangou Bed |
A lizard related to shinisaurs |
  | |||
|
L. acanthocaudata[81] |
Jianshangou or Dawangzhangzi bed |
A lizard related to geckos and skinks | ||||
|
X. zhaoi |
Jianshangou Bed |
A gliding lizard related to chameleons and dragon lizards | ||||
|
Y. tenuis |
Dawangzhangzi & Jingangshan Beds |
A lizard related to geckos and skinks | ||||
Turtles
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
M. liaoxiensis[82] |
Jianshangou Bed |
Reclassified as Ordosemys liaoxiensis[83] |
 | |||
|
M. manchoukuoensis[17] |
Jingangshan Bed |
|||||
|
O. liaoxiensis[83] |
Jianshangou Bed |
|||||
Mammals
Color key
|
Notes Uncertain or tentative taxa are in small text; |
The mammals listed below were compiled in a survey by Meng and colleagues in 2006, unless otherwise noted.[84]
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
A. yanensis[85] |
Beipiao |
Lujiatun Bed |
A eutherian |
     | ||
|
A. cifellii |
Lingyuan |
Dawangzhangzi Bed |
A spalacotheriid "symmetrodont" | |||
| Ambolestes[86] | A. zhoui | Nincheng | Jianshangou Bed | A eutherian | ||
|
C. lii |
Lingyuan |
Dawangzhangzi Bed |
A eutriconodont | |||
|
E. scansoria |
Lingyuan |
Dawangzhangzi Bed |
A tribosphenidan, possibly a eutherian or stem-therian | |||
|
G. zofiae |
Beipiao |
Lujiatun Bed |
A gobiconodont | |||
|
G. luoianus[88] |
Lujiatun Bed |
A gobiconodont; junior synonym of G. zofiae | ||||
|
J. jenkinsi |
Chaoyang |
Jianshangou Bed |
A eutriconodont | |||
|
J. liaoningensis |
Beipiao |
Lujiatun Bed |
An amphidontid | |||
|
J. cheni |
A eutriconodont | |||||
|
M. sinensis |
Chaoyang |
Jianshangou Bed |
A zhangeotheriid "symmetrodont" | |||
|
M. asiaticus[91] |
Beipiao |
Lujiatun Bed |
A zhangeotheriid "symmetrodont" | |||
|
M. lujiatunensis |
Beipiao |
Lujiatun Bed |
A gobiconodont | |||
| Origolestes | O. lii | A zhangeotheriid "symmetrodont" | ||||
| Ningchengodon | N. foxi[92] | Ningcheng | Ningcheng Basin | A partial right dentary. | A symmetrodont. | |
|
R. giganticus |
Beipiao |
Lujiatun Bed |
A gobiconodont | |||
|
R. robustus |
Beipiao |
Lujiatun Bed |
A large gobiconodont, which ate small dinosaurs | |||
|
S. lingyuanensis |
Lingyuan |
Jianshangou and Dawangzhangzi Beds |
A multituberculate | |||
|
S. szalayi |
Lingyuan |
Dawangzhangzi Bed |
A therian, initially interpreted as a metatherian and later reinterpreted as a eutherian | |||
|
Y. allini[93] |
Fengning[93] |
A eutricondodont | ||||
|
Z. quinquecuspidens |
Chaoyang |
Jianshangou Bed |
A zhangeotheriid "symmetrodont" | |||
Amphibians
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | County | Member | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
C. sanyanensis |
Sihetun |
Jianshangou Bed |
Junior synonym of Liaobatrachus |
 | ||
|
L. subsolanus |
Paozhanggou |
Fengshan Bed |
A urodelan | |||
|
L. grabaui |
Sihetun |
Jianshangou Bed |
A spadefoot toad | |||
|
L. zhaoi |
Beipiao & Heitizigou |
Lujiatun Bed & Jianshangou Bed |
A spadefoot toad | |||
|
Mesophryne |
M. beipiaoensis |
Beipiao & Heitizigou |
Lujiatun Bed & Jianshangou Bed |
Junior synonym of Liaobatrachus | ||
|
S. fengshanensis |
Paozhanggou |
Fengshan Bed |
A urodelan | |||
Fish
| Genus | Species | County | Member | Abundance | Notes | Images |
|---|---|---|---|---|---|---|
|
Hybodontoidea indet. |
Family, genus and species indeterminate |
An elasmobranch known from a single dorsal fin spine[94] |
    | |||
|
L. davidi |
Jianshangou & Dawangzhangzi Beds |
Also present in the Jiufotang Formation & Huajiying Formation |
||||
|
L. muroii |
Jingangshan Bed |
|||||
|
L. sinensis |
Jianshangou Bed |
|||||
|
M. mengae |
A lamprey | |||||
|
P. pani |
Jianshangou & Dawangzhangzi Bed |
Also present in the Jiufotang Formation |
A peipiaosteid fish related to sturgeons | |||
|
P. liui |
Dawangzhangzi Bed |
Also present in the Jiufotang & Huajiying Formations |
||||
|
S. liaoningensis |
Jianshangou Bed |
A bowfin | ||||
|
Y. longidorsalis |
Also present in the Huajiying Formation |
A peipiaosteid | ||||
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