Xitun Formation Explained

Xitun Formation
Type:	Geological formation
Period:	Devonian
Prilithology:	Calciferous mudstones
Namedfor:	Xitun village
Region:	Yunnan Province
Coordinates:	25°29.853'N and 103°46.309'E
Unitof:	Cuifengshan Group
Underlies:	Guijiatun Formation
Overlies:	Xiaxishancun Formation
Extent:	Qujing

The Xitun Formation is a palaeontological formation which is named after Xitun village in Qujing, a location in South China. This formation includes many remains of fossilized fish and plants of the Early Devonian period (Late Lochkovian).^{[1] [2]} It was originally referred to as the Xitun Member of the Cuifengshan Formation (now the Cuifengshan Group).^[3]

Fossil content

Vertebrates

Acanthodians

Acanthodians reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Ischnacanthidae	Genus indet.	Qujing.	4 isolated scales (V7218.1, 3, 6 & 8) & 2 longitudinal sections (V7218.4 & 7).	Similar to Ischnacanthus & Acanthodes, may be referrable to Youngacanthus.
Nostolepis	N. amplifica	Xitun, Xishan subdistrict, Qujing.^[4]	43 trunk scales.
	N. consueta	Xitun, Xishan subdistrict, Qujing.	Around 25 trunk scales.
	N. digitus	Xitun, Xishan subdistrict, Qujing.	28 trunk scales.
	N. qujingensis	Xitun, Xishan subdistrict, Qujing.	19 trunk scales.
	N. striata	Xitun, Xishan subdistrict, Qujing.	69 trunk scales.
	N. sp. indet.	Qujing.	Body scales.
Youngacanthus	Y. gracilis	Qujing.	Jaw elements & teeth.	An ischnacanthid.

Chondrichthyes

Chondrichthyes reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Changolepis	C. tricuspidus	Qujing.	10 scales of various growth stages.
Chondrichthyes	Genus indet.	Qujing.	4 isolated teeth (V7221.1, 2, 3 & 4).	May belong to Gualepis or Changolepis.
Gualepis	G. elegans	Xitun, Qilin district, Qujing.^[7]	Thousands of isolated scales.
Ohiolepis?	O.? xitunensis	Qujing.	A complete scale (V7233.1) & an incomplete scale (V7223.2).
Peilepis	P. solida	Qujing.	A body scale (V7222).

Jawless fish

Jawless fish reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Parathelodus	P. asiaticus	Qilin district, Qujing.^[8]	Body scales.	A thelodont also known from the Xishancun Formation.
	P. cornuformis	Qilin district, Qujing.	Body scales.	A thelodont also known from the Xishancun Formation.
	P. liaokuoensis	Qilin district, Qujing.	Body scales.	A thelodont also known from the Xishancun Formation.
	P. scitulus	Qilin district, Qujing.	A complete body scale (IVPP V 12156.1).	A thelodont also known from the Xishancun Formation.
	P. trilobatus	Qilin district, Qujing.	Body scales.	A thelodont also found in the Xishancun Formation.
	P. wangi	Qilin district, Qujing.	Body scales.	A thelodont also known from the Xishancun Formation.
	P. xitunensis	Qilin district, Qujing.	A complete body scale (IVPP V 26113.1).	A thelodont.
Turinia	T. asiatica	Qujing.	Multiple scales.	A thelodont.
Xitunaspis	X. magnus	Qujing.^[9]	4 headshields.	A galeaspid.

Placoderms

Placoderms reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Antiarchi	Unnamed antiarch	Qujing.	MNHN-CHD02 & V10515.	Originally referred to ?Xichonelepis.
Asterosteidae	Gen. et. sp. indet.	Qujing.^[10]	Part of the head shield.	Very similar to Gemuendina.
Chuchinolepis	C. gracilis	Qujing.	Detached plates.	A chuchinolepidid also known from the Xishancun Formation.
	C. qujingensis		Plates.	A chuchinolepidid also known from the Xishancun Formation.
	C. robusta	Qujing.	A detached AVL plate (V10512).	A chuchinolepidid.
	C. sulcata	Qujing.	Trunkshield, plates & incomplete pectoral fin.	A chuchinolepidid.
Gavinaspis	G. convergens	Qujing.^[11]	Skull remains.	A phyllolepid.
Parayunnanolepis	P. xitunensis		Almost-complete specimen.^[12]	A yunnanolepidid.
Phymolepis	P. cuifengshanensis	Cuifengshan and Liaokuoshan, Qujing.^[13]	Plates.	A yunnanolepidid also known from the Xishancun Formation.
	P. guoruii	Qujing.	Trunk-shields & plates.	A yunnanolepidid.
Szeaspis	S. yunnanensis	Qujing.^[14]	Neurocranium & associated skull roof (IVPP V 5810a-b).	Preoccupied genus name, renamed Szelepis.
Szelepis	S. yunnanensis	Qujing.	Neurocranium & associated skull roof (IVPP V 5810a-b).	An actinolepid originally named Szeaspis.
Yunnanolepis	Y. porifera	Qujing.		A yunnanolepidid also known from the Xishancun Formation.
	Y. sp.	Qujing.	A trunk-shield associated with part of skull roof (V10514).	A yunnanolepidid, specimen formerly assigned to Vanchienolepis.
Zhanjilepis	Z. aspratilis	Qujing.	Plates.	A yunnanolepidid also known from the Xishancun Formation.

Sarcopterygians

Sarcopterygians reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Achoania	A. jarvikii	Qujing.^[15]	Anterior cranial portion.	A basal lobe finned fish.
Diabolepis	D. speratus	Xichong, Qujing.^[16]	Multiple specimens.^[17]	A dipteriform originally named Diabolichthys.
Psarolepis	P. romeri	Xichong, Qujing.^[18]	4 anterior cranial portions, a posterior cranial portion, 2 complete lower jaws & an incomplete lower jaw.	A basal lobe finned fish.
Styloichthys	S. changae	Qujing.^[19]	Multiple specimens.	A basal coelacanth.^[20]
Youngolepis	Y. praecursor		Numerous specimens.^[21]	A basal lobe finned fish also known from the Bac Bun Formation.

Plants

Plants reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Gen. nov. A		Huaguo Hill, Shengfeng district of Qujing city.	Numerous specimens.
aff. Huia	aff. H. sp.	Huaguo Hill, Shengfeng district of Qujing city.	PKU-XH214.	A lycophyte.
Unnamed spike		Huaguo Hill, Shengfeng district of Qujing city.	A poorly preserved terminal spike (PKU-XH215a, 215b).	Probably from a zosterophyll.
Xitunia	X. spinitheca	Qujing.^[22]		A zosterophyll.
Zosterophyllum	Z. minorstachyum	Qujing.		A zosterophyll.
	Z. shengfengense	A building site at Huaguo Hill, Shengfeng District, Qujing City.^[23]	A nearly entire individual plant preserved as a compression (PUH-QXI01-1), and its counterpart (PUH-QXI01-1’).	A zosterophyll.

See also

• List of fossil sites— (with link directory)

Notes and References

1. Zhu . Min . 1996-01-01 . The phylogeny of the Antiarcha (Placodermi, Pisces), with the description of Early Devonian antiarchs from Qujing, Yunnan, China . Bull. Mus. Nat. Hist. Natur., Sér.
2. Xue . Jinzhuang . March 2012 . Lochkovian plants from the Xitun Formation of Yunnan, China, and their palaeophytogeographical significance . Geological Magazine . en . 149 . 2 . 333–344 . 10.1017/S001675681100077X . 2012GeoM..149..333X . 129280508 . 0016-7568.
3. Wang . Nianzhong. . Wang . Nianzhong . 1984 . Thelodont, acanthodian, and chondrichthyan fossils from the Lower Devonian of southwestern China . Proceedings of the Linnean Society of New South Wales . 107 . 419–441 . 0370-047X.
4. Li . Qiang . Cui . Xindong . Andreev . Plamen Stanislavov . Zhao . Wenjin . Wang . Jianhua . Peng . Lijian . Zhu . Min . 2021-05-07 . Nostolepis scale remains (stem Chondrichthyes) from the Lower Devonian of Qujing, Yunnan, China . PeerJ . en . 9 . e11093 . 10.7717/peerj.11093 . 34012725 . 8109008 . 2167-8359 . free .
5. Zhu . Min . Meemannia eos, a basal sarcopterygian fish from the Lower Devonian of China – expanded description and significance . Academia.
6. Lu . Jing . Giles . Sam . Friedman . Matt . den Blaauwen . Jan L. . Zhu . Min . 2016-06-20 . The Oldest Actinopterygian Highlights the Cryptic Early History of the Hyperdiverse Ray-Finned Fishes . Current Biology . English . 26 . 12 . 1602–1608 . 10.1016/j.cub.2016.04.045 . 0960-9822 . 27212403. 3928790 . free .
7. Cui . Xindong . Qu . Qingming . Andreev . Plamen S. . Li . Qiang . Mai . Huijuan . Zhu . Min . 2021-03-04 . Modeling scale morphogenesis in a Devonian chondrichthyan and scale growth patterns in crown gnathostomes . Journal of Vertebrate Paleontology . en . 41 . 2 . e1930018 . 10.1080/02724634.2021.1930018 . 2021JVPal..41E0018C . 237517966 . 0272-4634.
8. Xin-Dong . C. U. I. . Qiang . L. I. . Min . Z. H. U. . Min . Z. H. U. . 2020-01-20 . New material of thelodonts from Lochkovian (Lower Devonian) of Qujing, Yunnan, China . Vertebrata PalAsiatica . en . 58 . 1 . 1 . 10.19615/j.cnki.1000-3118.190612 . 2096-9899.
9. Hao-Ran . Sun . Gai . Zhikun . Jia-Chen . Cai . Qiang . L I . April 2022 . Xitunaspis, a new eugaleaspid fish (Eugaleaspiformes, Galeaspida) from the Lower Devonian of Qujing, Yunnan . Vertebrata PalAsiatica . 10.19615/j.cnki.2096-9899.220412.
10. Jun-Qing . Wang . 1991-04-19 . Discovery of asterosteidae from Lower Devonian in Eastern Yuannan . Vertebrata PalAsiatica . en . 29 . 2 . 162 . 2096-9899.
11. Dupret . V. . Zhu . M. . 30 November 2007 . The earliest phyllolepid (Placodermi, Arthrodira) from the Late Lochkovian (Early Devonian) of Yunnan (South China) . Geological Magazine . en . 145 . 2 . 257–278 . 10.1017/S0016756807004207 . 129360262 . 1469-5081.
12. Zhu . Min . Yu . Xiaobo . Choo . Brian . Wang . Junqing . Jia . Liantao . 2012-06-23 . An antiarch placoderm shows that pelvic girdles arose at the root of jawed vertebrates . Biology Letters . 8 . 3 . 453–456 . 10.1098/rsbl.2011.1033 . 3367742 . 22219394.
13. Wang . Yajing . Zhu . Min . 2018-05-28 . Redescription of Phymolepis cuifengshanensis (Antiarcha: Yunnanolepididae) using high-resolution computed tomography and new insights into anatomical details of the endocranium in antiarchs . PeerJ . 6 . e4808 . 10.7717/peerj.4808 . 2167-8359 . 5978403 . 29868260 . free .
14. Dupret . Vincent . Zhu . Min . Wang . Jun-Qing . 2017-03-04 . Redescription of Szelepis Liu, 1981 (Placodermi, Arthrodira), from the Lower Devonian of China . Journal of Vertebrate Paleontology . en . 37 . 2 . e1312422 . 10.1080/02724634.2017.1312422 . 2017JVPal..37E2422D . 90912807 . 0272-4634.
15. Zhu . Min . Yu . Xiaobo . Ahlberg . Per E. . 2001 . A primitive sarcopterygian fish with an eyestalk . Nature . 410 . 6824 . 81–84 . 10.1038/35065078 . 11242045 . 4416579 . 0028-0836.
16. Chang . Meemann . Meemann Chang . Yu . Xiaobo . January 1984 . Structure and phylogenetic significance of Diabolichthys speratus gen. et sp. nov., a new dipnoan-like form from the Lower Devonian of eastern Yunnan, China . Proceedings of the Linnean Society of New South Wales . 107 . 3 . 171–184.
17. Chang . Meemann . Meemann Chang . January 1995 . Diabolepis and its bearing on the relationships between porolepiforms and dipnoans . Bulletin du Muséum National d'Histoire Naturelle, Section C . 17 . 1 . 235–268.
18. Yu . Xiaobo . 1998 . A New Porolepiform-Like Fish, Psarolepis romeri, gen. et sp. nov. (Sarcopterygii, Osteichthyes) from the Lower Devonian of Yunnan, China . Journal of Vertebrate Paleontology . 18 . 2 . 261–274 . 10.1080/02724634.1998.10011055 . 4523897 . 1998JVPal..18..261Y . 0272-4634.
19. Zhu . Min . Yu . Xiaobo . September 2002 . A primitive fish close to the common ancestor of tetrapods and lungfish . Nature . en . 418 . 6899 . 767–770 . 10.1038/nature00871 . 12181564 . 2002Natur.418..767Z . 4389974 . 1476-4687.
20. Friedman . Matt . January 2007 . Styloichthys as the oldest coelacanth: Implications for early osteichthyan interrelationships . Journal of Systematic Palaeontology . en . 5 . 3 . 289–343 . 10.1017/S1477201907002052 . 2007JSPal...5..289F . 83712134 . 1477-2019.
21. Cui . Xindong . Friedman . Matt . Qiao . Tuo . Yu . Yilun . Zhu . Min . 2022-05-02 . The rapid evolution of lungfish durophagy . Nature Communications . en . 13 . 1 . 2390 . 10.1038/s41467-022-30091-3 . 35501345 . 9061808 . 2022NatCo..13.2390C . 248504614 . 2041-1723.
22. Xue . Jinzhuang . 2009-06-10 . Two Zosterophyll Plants from the Lower Devonian (Lochkovian) Xitun Formation of Northeastern Yunnan, China . Acta Geologica Sinica - English Edition . en . 83 . 3 . 504–512 . 10.1111/j.1755-6724.2009.00057.x. 2009AcGlS..83..504X . 131021391 .
23. Hao . Shougang . Xue . Jinzhuang . Guo . Dali . Wang . Deming . January 2010 . Earliest rooting system and root : shoot ratio from a new Zosterophyllum plant . New Phytologist . en . 185 . 1 . 217–225 . 10.1111/j.1469-8137.2009.03056.x . 19825018 . 5638825 . 0028-646X. free .