Xitun Formation

Xitun Formation
Stratigraphic range: Early Devonian (Lochkovian) PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Cuifengshan Group [1]
Underlies	Guijiatun Formation [2]
Overlies	Xiaxishancun Formation [2]
Lithology
Primary	Calciferous mudstones [2]
Location
Coordinates	25°29.853'N and 103°46.309'E [2]
Region	Yunnan Province
Country	China
Extent	Qujing
Type section
Named for	Xitun village

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

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.

Vertebrates

Acanthodians

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

Actinopterygians

Actinopterygians reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Meemannia	M. eos	Xitun village, Qujing. [5]		An early ray-finned fish, formerly thought to be a lobe finned fish. [6]

Arthropods

Arthropods reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Qujingopterus [7]	Q. spineus			A stylonurid eurypterid

Chondrichthyes

Chondrichthyes reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Changolepis	C. tricuspidus	Qujing. [3]	10 scales of various growth stages. [3]
Chondrichthyes	Genus indet.	Qujing. [3]	4 isolated teeth (V7221.1, 2, 3 & 4).	May belong to Gualepis or Changolepis .
Gualepis	G. elegans	Xitun, Qilin district, Qujing. [8]	Thousands of isolated scales. [3] [8]
Ohiolepis?	O.? xitunensis	Qujing. [3]	A complete scale (V7233.1) & an incomplete scale (V7223.2). [3]
Peilepis	P. solida	Qujing. [3]	A body scale (V7222). [3]

Jawless fish

Jawless fish reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Parathelodus	P. asiaticus	Qilin district, Qujing. [9]	Body scales. [9]	A thelodont also known from the Xishancun Formation.
	P. cornuformis	Qilin district, Qujing. [9]	Body scales. [9]	A thelodont also known from the Xishancun Formation.
	P. liaokuoensis	Qilin district, Qujing. [9]	Body scales. [9]	A thelodont also known from the Xishancun Formation.
	P. scitulus	Qilin district, Qujing. [9]	A complete body scale (IVPP V 12156.1). [9]	A thelodont also known from the Xishancun Formation.
	P. trilobatus	Qilin district, Qujing. [9]	Body scales. [9]	A thelodont also found in the Xishancun Formation.
	P. wangi	Qilin district, Qujing. [9]	Body scales. [9]	A thelodont also known from the Xishancun Formation.
	P. xitunensis	Qilin district, Qujing. [9]	A complete body scale (IVPP V 26113.1). [9]	A thelodont.
Turinia	T. asiatica	Qujing. [3]	Multiple scales. [3]	A thelodont.
Xitunaspis	X. magnus	Qujing. [10]	4 headshields. [10]	A galeaspid.

Placoderms

Placoderms reported from the Xitun Formation
Genus	Species	Presence	Material	Notes	Images
Antiarchi	Unnamed antiarch	Qujing. [1]	MNHN-CHD02 & V10515. [1]	Originally referred to ?Xichonelepis.
Asterosteidae	Gen. et. sp. indet.	Qujing. [11]	Part of the head shield. [11]	Very similar to Gemuendina . [11]
Chuchinolepis	C. gracilis	Qujing. [1]	Detached plates. [1]	A chuchinolepidid also known from the Xishancun Formation.
	C. qujingensis		Plates. [1]	A chuchinolepidid also known from the Xishancun Formation.
	C. robusta	Qujing. [1]	A detached AVL plate (V10512). [1]	A chuchinolepidid.
	C. sulcata	Qujing. [1]	Trunkshield, plates & incomplete pectoral fin. [1]	A chuchinolepidid.
Gavinaspis	G. convergens	Qujing. [12]	Skull remains. [12]	A phyllolepid.
Parayunnanolepis	P. xitunensis		Almost-complete specimen. [13]	A yunnanolepidid.
Phymolepis	P. cuifengshanensis	Cuifengshan and Liaokuoshan, Qujing. [1] [14]	Plates. [1] [14]	A yunnanolepidid also known from the Xishancun Formation.
	P. guoruii	Qujing. [1]	Trunk-shields & plates. [1]	A yunnanolepidid.
Szeaspis	S. yunnanensis	Qujing. [15]	Neurocranium & associated skull roof (IVPP V 5810a-b). [15]	Preoccupied genus name, renamed Szelepis .
Szelepis	S. yunnanensis	Qujing. [15]	Neurocranium & associated skull roof (IVPP V 5810a-b). [15]	An actinolepid originally named Szeaspis.
Yunnanolepis	Y. porifera	Qujing. [1]		A yunnanolepidid also known from the Xishancun Formation.
	Y. sp.	Qujing. [1]	A trunk-shield associated with part of skull roof (V10514). [1]	A yunnanolepidid, specimen formerly assigned to Vanchienolepis .
Zhanjilepis	Z. aspratilis	Qujing. [1]	Plates. [1]	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. [16]	Anterior cranial portion. [16]	A basal lobe finned fish.
Diabolepis	D. speratus	Xichong, Qujing. [17]	Multiple specimens. [17] [18]	A dipteriform originally named Diabolichthys .
Psarolepis	P. romeri	Xichong, Qujing. [19]	4 anterior cranial portions, a posterior cranial portion, 2 complete lower jaws & an incomplete lower jaw. [19]	A basal lobe finned fish.
Styloichthys	S. changae	Qujing. [20]	Multiple specimens. [20]	A basal coelacanth. [21]
Youngolepis	Y. praecursor		Numerous specimens. [22]	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. [2]	Numerous specimens. [2]
aff. Huia	aff. H. sp.	Huaguo Hill, Shengfeng district of Qujing city. [2]	PKU-XH214. [2]	A lycophyte.
Unnamed spike		Huaguo Hill, Shengfeng district of Qujing city. [2]	A poorly preserved terminal spike (PKU-XH215a, 215b). [2]	Probably from a zosterophyll.
Xitunia	X. spinitheca	Qujing. [23]		A zosterophyll.
Zosterophyllum	Z. minorstachyum	Qujing. [23]		A zosterophyll.
	Z. shengfengense	A building site at Huaguo Hill, Shengfeng District, Qujing City. [24]	A nearly entire individual plant preserved as a compression (PUH-QXI01-1), and its counterpart (PUH-QXI01-1’). [24]	A zosterophyll.

See also

• List of fossil sites— (with link directory)

References

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2. Xue, Jinzhuang (March 2012). "Lochkovian plants from the Xitun Formation of Yunnan, China, and their palaeophytogeographical significance". Geological Magazine. 149 (2): 333–344. Bibcode:2012GeoM..149..333X. doi:10.1017/S001675681100077X. ISSN   0016-7568. S2CID   129280508.
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