Ergilin Dzo Formation Explained

Ergilin Dzo Formation
Type:	Geological formation
Period:	Paleogene
Namedby:	Dashzeveg
Year Ts:	1993
Region:	Dornogovi Province
Country:	Mongolia
Subunits:	From top to bottom: Khetsu Tsav member Ergilin member Shavag member Sevkhul member Zangut member Khubsugul member

The Ergilin Dzo Formation (formerly known as the Ardyn Obo Formation), is a geologic formation in southeastern Mongolia. It preserves fossils of a wide variety of animals, which date back to the late Eocene epoch. The type fauna of the Ergilian Asian land mammal age is defined by the mammalian fossils of this formation.^[1]

Depositional environment

Based on the presence of brontotheres and the abundance of herbivorous low-crowned mammals, the Ergilin Dzo Formation has been estimated to be humid and warm/hot with a relatively-closed area.^[2] ^[3] However, the absence of primates and rarity of crocodyliforms (known from one specimen currently) in this formation may suggest the paleoenvironment had open areas and was more arid than similarly aged faunal assemblages from elsewhere in Eurasia. Sedimentary analyses suggest the Ergilin Dzo Formation was a floodplain environment with a braided stream network formed by fluvial systems.^[4]

Fossil content

In their review of the vertebrate fauna of the formation, Tsubamoto et al. (2022) found that 77 genera and 104 species of vertebrate have been reported from the Ergilin Dzo Formation, representing 22 orders and 49 families. Fossils of mammals, reptiles (including birds), fish and amphibians have all been recovered from the formation since the early 20th Century.

Mammals

81 mammal species have been found in the Ergilin Dzo Formation, with perissodactyls being the most diverse group (33 species reported). Ruminant artiodactyls, rhinocerotoids and brontotheres are the most abundant groups in terms of collected specimen numbers.

Artiodactyls

Artiodactyls reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Anthracotheriidae indet.	Indeterminate	Ergilin Dzo locality.^[5]		Left astragalus.	An anthracothere.
cf. Bothriodon	cf. B. sp.	Ergilin Dzo & Khoer Dhan localities.		Jaw & limb elements.	An anthracothere.
Brachyhyops	B. trofimovi	Khoer Dzhan locality.^[6]		Jaw elements.	An entelodontid.
Brachyhyops	B. sp.	Ergilin Dzo locality.		Right maxilla fragment.	An entelodontid.
Entelodon	E. gobiensis	Khoer Dzhan & Ergilin Dzo localities.^[7]			An entelodontid.
Eumeryx	E. sp.				A deer.
Gobiomeryx	G. dubius				A leptomerycid.
Lophiomeryx	L. angarae				A lophiomerycid.
Lophiomeryx	L. sp.				A lophiomerycid.
Miomeryx	M. altaicus				A leptomerycid.
Miomeryx	M. sp.				A leptomerycid.
Praetragulus	P. electus	Khoer Dzhan locality.^[8]		Numerous jaw & limb elements.	A hypertragulid.
Praetragulus	P. gobiae	Ergilin Dzo locality.		Jaw elements.	A hypertragulid.

Didymoconids

Didymoconids reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Ardynictis	A. furunculus			Skull & jaws.^[11]
Ergilictis	E. reshetovi	Ergilin Dzo locality.^[12]		Jaw elements.

Eulipotyphlans

Eulipotyphlans reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Amphechinus	A. sp.	Ergilin Dzo locality.^[13]	Sevkhul Member.	Left dentary fragment.	A hedgehog.
Ictopidium?	I.? sp.				A changlelestid.
Oligochenus	O. grandis	Ergilin Dzo locality.	Sevkhul Member.	Right dentary fragment.	A gymnure.
Palaeoscaptor?	P.? sp.				A hedgehog.
Soricinae indet.	Indeterminate				A shrew.
Tupaiodontinae indet.	Indeterminate	Ergilin Dzo locality.	Ergilin Member.	Premolar.	A changlelestid.

Ferae

Ferae reported from the Ergolin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Alagtsavbaatar	A. indigenus	Alag Tsav & Khoer Dzhan localities.^[14]		Jaw & limb elements.	A small feliform.
Amphicyonidae indet.	Indeterminate	Ergilin Dzo locality.^[15]		Tooth.	A bear-dog.
Asiavorator	A. gracilis	Ergilin Dzo locality.		Right mandible fragment.	A small feliform.
Eofelis	E. sp.	Khoer Dzhan locality.		Jaw elements.	A nimravid.
Hyaenodon	H. chunkhtensis	Khoer Dzhan locality.^[16] ^[17]		Left mandibular corpus.	A hyaenodont.
	H. eminus	Khoer Dzhan & Ergilin Dzo localities.		Jaw elements.	A hyaenodont.
	H. gigas	Khoer Dzhan locality.			A hyaenodont.
	H. incertus	Khoer Dzhan & Ergilin Dzo localities.			A hyaenodont.
	H. mongoliensis	Khoer Dzhan & Ergilin Dzo localities.			A hyaenodont.
	H. pervagus	Khoer Dzhan & Ergilin Dzo localities.			A hyaenodont.
	H. pumilus			Mandibular ramus.	A hyaenodont.
Nimravus	N. mongoliensis	Khoer Dzhan locality.		Jaw & limb elements.	A nimravid.
Proviverrinae indet.	Indeterminate	Khoer Dzhan locality.		Tooth.	A hyaenodont.

Gliriformes

Gliriformes reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Ardynomys	A. olseni			Lower jaw.	A rodent.
	A. silentiumis				A rodent.
	A. sp.				A rodent.
Desmatolagus	D. ardynense				A lagomorph.
	D. gobiensis				A lagomorph.
	D. robustus			Lower jaws.	A lagomorph.
Eucricetodon	E. sp.				A rodent.
Lagomorpha indet.	Indeterminate				A lagomorph.
Zofiagale	Z. ergilensis	Ergilin Dzo locality.^[18]		Right dentary.	An anagalid.

Mesonychians

Mesonychians reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Metahapalodectes	M. sp.				A hapalodectid.
Mongolestes	M. hadrodens				A mesonychid.

Perissodactyls

Perissodactyls reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
cf. Allacerops	cf. A. sp.	Khoer Dzhan.^[19]		Jaw elements.	An eggysodontid.
Amynodon	A. sp.				An amynodont.
Amynodontopsis	A. lunanensis				An amynodont.
Ardynia	A. praecox	Khoer Dzhan.	Sevkhul & Ergilin members.	Jaw elements.	A hyracodontid.
Ardynia	A. sp.	Khoer Dzhan.	Sevkhul & Ergilin members.	Jaw fragments.	A hyracodontid.
Armania	A. asiana	Khoer Dzhan & Ergilin Dzo.	Sevkhul & Ergilin Members.	Jaw elements.	A hyracodontid.
Brontotheriidae indet.	Indeterminate				A brontothere.
Cadurcodon	C. ardynensis				An amynodont.
Cadurcodon	C. sp.				An amynodont.
Cadurcotherium	C. progressus				An amynodont.
cf. Deperetella	cf. D. sp.				A deperetellid.
Embolotherium	E. andrewsi			Skull.^[20]	A brontothere.
	E. grangeri	Khoer Dzhan.		Partial skull.	A brontothere.
	E. sp.				A brontothere.
Eomoropus	E. sp.				An eomoropid.
Eubrontotherium	E. clarnoensis	Ergilin Dzo.		Partial skeleton.	A brontothere.
Juxia	J. borissiaki	Ergilin Dzo locality.	Ergilin Member.	Jaws & teeth.	A paraceratheriid.
cf. Nasamplus	cf. N. progressus				A brontothere.
Paraceratheriidae indet.	Indeterminate	Khoer Dzhan.	Ergilin Member.	Teeth.	Initially reported as Urtinotherium (or Paraceratherium) sp.
Paraceratherium	P. parvum				A paraceratheriid.
Paracolodon	P. inceptus				A helaletid.
Paracolodon	P. sp.				A helaletid.
Prohyracodon	P. meridionalis	Khoer Dzhan.	Sevkhul Member.	Jaw elements.	A hyracodontid.
	P. obrutschewi				A hyracodontid.
	?P. parvum	Khoer Dzhan.	Zangut-Sevkhul member.	Jaw elements.	A hyracodontid.
Protembolotherium	P. efremovi	Ergilin Dzo.		Skull elements.	A brontothere.
Ronzotherium	R. brevirostris				A rhino.
	R. orientale	Ergilin Dzo, Bayan Tsav ravine & Khoer Dzhan.	Ergilin Member.	Jaw elements.	A rhino.
	R. sp.	Khoer Dzhan.	Ergilin Member.	Fragment of mandibular ramus.	A rhino.
Schizotherium	S. avitum				A chalicothere.
Sharamynodon	S. mongoliensis				An amynodont.
Teleolophus	T. magnus				A deperetellid.
cf. Zaisanamynodon	cf. Z. sp.				An amynodont.

Reptiles

Reptiles are represented by 20 known species in the formation, with 11 of these being birds.

Birds

Birds reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Accipitridae indet.	Indeterminate	Khoer Dzhan.^[21]		Leg bones.	An accipitrid.
Anatidae indet.	Indeterminate	Khoer Dzhan.			An anatid.
Ardeidae indet.	Indeterminate	Khoer Dzhan.			A heron.
Cygninae indet.	Indeterminate	Khoer Dzhan.			A swan.
Eogrus	E. sp.	Ergilin Dzo.			An eogruid.
Ergilornis	E. minor	Ergilin Dzo.			An eogruid.
	E. rapidus	Ergilin Dzo.			An eogruid.
	E. sp.				An eogruid.
Lari indet.	Indeterminate	Khoer Dzhan.		Skull fragment.	A shorebird.
Rallidae indet.	Indeterminate	Khoer Dzhan.			A rail.
Sonogrus	S. gregalis				An eogruid.

Squamates

Squamates reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Agamidae indet.	Indeterminate				An agamid lizard.
Lacertilia indet.	Indeterminate				A lizard.

Turtles

Turtles reported from the Ergilin Dzo Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Chrysemys	C. sp.
Emydidae gen. et. sp. indet.	Indeterminate				A terrapin.
Ergilemys	E. insolitus				A tortoise.
?Melanochelys	?M. elongata
Platysternidae gen. et. sp. indet.	Indeterminate
Trionychidae gen. et. sp. indet.	Indeterminate				A softshell turtle.

Fish

Fish reported from the Formation
Genus	Species	Presence	Stratigraphic member	Material	Notes	Images
Amia	A. sp.				A bowfin.
Parasilurus	P. sp.				A catfish.

Notes and References

Tsubamoto . Takehisa . Tsogtbaatar . Khishigjav . Chinzorig . Tsogtbaatar . Egi . Naoko . 2022 . A brief review of the updated fossil vertebrate fauna of the upper Eocene Ergilin Dzo Formation, southeastern Mongolia . Memoirs of the Faculty of Science, Ehime University . 24 . 64–83.
Book: Prothero, Donald R. . The Eocene-Oligocene transition: paradise lost . 1994 . Columbia University Press . 978-0-231-08091-0 . Critical moments in paleobiology and earth history series . New York.
Tsubamoto . T. . Egi . N. . Takai . M. . Sein . C. . Maung . Maung . 2005 . Middle Eocene ungulate mammals from Myanmar: a review with description of new specimens . Acta Palaeontologica Polonica. 55777375 .
Watabe . Mahito . 2010-03-31 . Lithostratigraphic and sedimentological analysis of the upper Eocene Ergilin Dzo Formation of Ergilin Dzo locality, Mongolia . Hayashibara Museum of Natural Sciences Research Bulletin . 3 . 149–153.
Tsubamoto . Takehisa . 2020-03-31 . Additional specimens of the Anthracotheriidae (Mammalia; Artiodactyla) from the upper Eocene Ergilin Dzo Formation of Mongolia . Hayashibara Museum of Natural Sciences Research Bulletin . 3 . 143–147.
Tsubamoto . Takehisa . Saneyoshi . Mototaka . Watabe . Mahito . Tsogtbaatar . Khishigjav . Mainbayar . Buurei . 2011-12-01 . The Entelodontid Artiodactyl Fauna from the Eocene Ergilin Dzo Formation of Mongolia with Comments on Brachyhyops and the Khoer Dzan Locality . Paleontological Research . en . 15 . 4 . 258–268 . 10.2517/1342-8144-15.4.258 . 1342-8144.
Watabe . Mahito . 2013-11-29 . New specimens of Entelodon gobiensis (Mammalia; Artiodactyla; Entelodontidae) from the Eocene Ergilin Dzo Formation, Mongolia . Bull. Res. Inst. Nat. Sci., Okayama Univ. Of Sci. . 39 . 37–41.
Book: Vislobokova, I. A. (Inessa Anatolévna) . A new representative of the Hypertraguloidea (Tragulina, Ruminantia) from the Khoer-Dzan locality in Mongolia, with remarks on the relationships of the Hypertragulidae . 1998 . New York, NY : American Museum of Natural History . American Museum of Natural History Library.
Dashzeveg . Demberliyn . Russell . Donald E. . December 1992 . Extension of dyspternine Pantolestidae (Mammalia, Cimolesta) in the Early Oligocene of Mongolia . Geobios . en . 25 . 5 . 647–650 . 10.1016/0016-6995(92)80104-L.
Tsubamoto . Takehisa . Tsogtbaatar . Khishigjav . Saneyoshi . Mototaka . Buuvei . Mainbayar . January 2011 . A new specimen of Gobiopithecus khan (Mammalia; Pantolesta) from the Eocene Ergilin Dzo Formation, Mongolia . Journal of Fossil Research . 44 . 1 . 20–23.
Matthew . William Diller . Granger . Walter . 1925-10-27 . New creodonts and rodents from the Ardyn Obo Formation of Mongolia . American Museum Novitates . 193. 2246/4476 .
Lopatin . Alexey . January 1997 . New Oligocene Didymoconidae (Mesonychia, Mammalia) from Mongolia and Kazakhstan . Paleontological Journal . 31 . 1 . 108–119.
Lopatin . Alexey . January 2005 . Late Paleogene Erinaceidae (Insectivora, Mammalia) from the Ergilin Dzo locality, Mongolia . Paleontological Journal . 39 . 1 . 85–92.
Egi . Naoko . Tsubamoto . Takehisa . Saneyoshi . Mototaka . Tsogtbaatar . Khishigjav . Watabe . Mahito . Mainbayar . Buuvei . Chinzorig . Tsogtbaatar . Khatanbaatar . Purevdorg . 2016-02-17 . Taxonomic revisions on nimravids and small feliforms (Mammalia, Carnivora) from the Upper Eocene of Mongolia . Historical Biology . en . 28 . 1–2 . 105–119 . 10.1080/08912963.2015.1012508 . 0891-2963.
Egi . Naoko . Tsubamoto . Takehisa . Tsogtbaatar . Khishigjav . 2009 . New Amphicyonid (Mammalia: Carnivora) from the Upper Eocene Ergilin Dzo Formation, Mongolia . Paleontological Research . 13 . 3 . 245 . 1342-8144.
Tsubamoto . Takehisa . Watabe . Mahito . Tsogtbaatar . Khishigjav . 2008-06-12 . Hyaenodon chunkhtensis and the hyaenodontid fauna from the upper Eocene Ergilin Dzo Formation of Mongolia . Journal of Vertebrate Paleontology . en . 28 . 2 . 559–564 . 10.1671/0272-4634(2008)28[559:HCATHF]2.0.CO;2 . 0272-4634.
Lavrov . A. V. . July 2019 . New Material on Small Hyenodons (Hyaenodontinae, Creodonta) from the Paleogene of Mongolia . Paleontological Journal . en . 53 . 4 . 418–431 . 10.1134/S0031030119040063 . 0031-0301.
López-Torres . Sergi . Fostowicz-Frelik . Łucja . 2018-09-17 . A new Eocene anagalid (Mammalia: Euarchontoglires) from Mongolia and its implications for the group's phylogeny and dispersal . Scientific Reports . en . 8 . 1 . 13955 . 10.1038/s41598-018-32086-x . 2045-2322 . 6141491 . 30224674.
Dashzeveg . D . 1991 . Hyracodontids and rhinocerotids (Mammalia, Perissodactyla, Rhinocerotoidea) from the Paleogene of Mongolia . Palaeovertebrata . 21 . 1–84.
Mihlbachler . Matthew C. . 2008 . Species Taxonomy, Phylogeny, and Biogeography of the Brontotheriidae (Mammalia: Perissodactyla) . Bulletin of the American Museum of Natural History . en . 311 . 1 . 1 . 10.1206/0003-0090(2008)501[1:STPABO]2.0.CO;2 . 0003-0090.
Kurochkin . E. N. . 1976-05-21 . A survey of the Paleogene birds of Asia . Collected Papers in Avian Paleontology Honoring the 90th Birthday of Alexander Wetmore . 27 . 75–86.
Iijima . Masaya . Tsubamoto . Takehisa . Tsogtbaatar . Khishigjav . Chinzorig . Tsogtbaatar . Baasankhuu . Soyol . 2019 . Discovery of a crocodyliform tooth from the upper Eocene Ergilin Dzo Formation, Mongolia . Acta Palaeontologica Polonica . 64 . 10.4202/app.00633.2019. free .