The Tsagaantsav Formation, Tsagantsab Formation or Tsagan-Tsab Formation (Russian: Tsagaantsav Svita) is an

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

(

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.6 ± 2 Ma and 125.77 (million years ago). The Hauterivian is preceded by the Valangi ...

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...

) geologic formation in Mongolia.Tsagaantsav Formation
in the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

Indeterminate

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

and psittacosaurid remains have been recovered from the formation.Weishampel et al., 2004, pp.517-607 Remains of the pterosaur ''

Noripterus ''Noripterus'' (meaning "lake wing" from Mongolian language, Mongolian ''nuur'', "lake" and Greek ''pteron'', "wing") is a genus of dsungaripteridae, dsungaripterid pterodactyloidea, pterodactyloid pterosaur from Lower Cretaceous-age Wuerho Ptero ...

'', which were originally given their own genus, "Phobetor" have also been recovered from the formation.Barrett et al., 2008Lü et al., 2009 Graham et al. 2001 reported radiometric dates of 131 and 126 Ma from the formation.Tsagan-Tsab well
in the

Fossil content

The following fossils were reported from the

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s of the formation: *

Pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

s ** '' Noripterus complicidens'' *

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s ** '' Psittacosaurus sp.'' ** Sauropoda indet. ** Theropoda indet. *

Lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

s ** Dorsetisauridae indet. ;Insects * '' Khutelchalcis gobiensis'' * '' Eopelecinus fragilis'' * '' E. minutus'' * '' Praeichneumon townesi'' * '' Eobraconus inopinatus'' * '' Westratia femorata'' * '' W. pachygaster'' * '' W. pentadecamera'' * '' Langtonius cynaricaudatus'' * '' Eugenodiamesa makarchenkoi'' * '' Jurochlus adustus'' * '' Ellia khara'' * '' Protanyderus mesozoicus'' * '' Metatrichopteridium cladistorum'' * '' Plectrocentropus sulis'' * '' Eoclipsis mongolica'' * '' Coptoclavisca nigricollinus'' * '' Cretorabus orientalis'' * '' Mesaclopus mongolicus'' * '' Chinocimberis dispersus'' * '' Megametrioxenoides longus'' * '' Uroperla lacerata'' * '' Trianguliperla quassa'' * '' Aphaorus curtipes'' * '' Juleyrodes ?gilli'' * '' Izinabis kerzhneri'' * '' Siberiogenites medius'' * '' Torephemera longipes'' * '' Leptoneta calyptrata'' * '' Albisca tracheata'' * '' Epeoromimus infractus'' * '' Osmylogramma martinsoni''Ponomarenko, 1992 * Juraphididae indet.

Fossil content

See also