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

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

(

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 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the Va ...

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

) geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in Mongolia.Tsagaantsav Formation
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) 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 bo ...

and psittacosaurid remains have been recovered from the formation.Weishampel et al., 2004, pp.517-607 Remains of the pterosaur '' Noripterus'', 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 In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

to lacustrine

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

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.Blatt ''et al.'' 1980, p ...

s of the formation: *

Pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is 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 to ...

s ** '' Dsungaripterus parvus'' ** '' Noripterus complicidens'' *

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

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

Lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

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