Mt. Uskuk, Ondai Sair (AMNH 3rd expedition) (Cretaceous of Mongolia)

Also known as Andai-Sayr

Where: Mongolia (45.1° N, 101.6° E: paleocoordinates 46.2° N, 101.7° E)

• coordinate estimated from map

• small collection-level geographic resolution

When: Anda-Khuduk Formation, Aptian (125.0 - 113.0 Ma)

• "paper shales" level

• bed-level stratigraphic resolution

Environment/lithology: lacustrine; shale

• "We found the fish-bearing paper shales associated with sandstones in which were sauropod reptiles at Ondai Sair. At the Oshih (Ashile) basin we searched the paper shales this year again for fossils, but found only the remains of a few plants, too badly macerated prior to deposition to be identified. The paper shales of the Oshih basin carry gypsum crystals, which perhaps points to bitter waters in which the fauna of Ondai Sair could not live. The Oshih and Ondai Sair basins are very probably continuous and form one basin. Sauropods and primitive predentates are found in each locality, although perhaps there is a slight difference between the two faunas. At Oshih the paper shales lie far higher in the series, not less than five hundred feet above the chief sauropod beds; but a few large sauropod vertebrae were seen only one hundred feet below a horizon which, on other grounds, we believe is correlated with the paper shales. At Ondai Sair, as I have said, the sauropods are found close to the paper shales and essentially of the same age...Clearly, there is a great unconformity beneath the Oshih and Ondai Sair and, so far as we know, these basins, which carry the paper shales, date the beginning of the basin or gobi sedimentation; that is, the beginning of deposition of shallow masses of continental sediments-alluvial fans, flood-plains, deltas, playa lake deposits and, locally, deposits in shallow but more permanent lakes. These deposits are but little disturbed and it is in them that all the vertebrate fossils are found."

Size classes: macrofossils, mesofossils

Preservation: adpression

Collected by Charles P. Berkey & F.K. Morris; reposited in the AMNH

Collection methods: quarrying, surface (float), surface (in situ), mechanical,

• " These were specimens were collected by Messrs. CharlesP. Berkey and F.K. Morris, on the Third Asiatic Expedition of the Museum."

Primary reference: T. D. A. Cockerell. 1924. Fossils in the Ondai Sair Formation Mongolia. Bulletin of the American Museum of Natural History 51:129-144 [M. Clapham/J. Karr]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 138728: authorized by Matthew Clapham, entered by Jered Karr on 26.01.2013

Creative Commons license: CC BY (attribution)

Taxonomic list

 Ephemeroptera - Hexagenitidae
Ephemeropsis trisetalis Eichwald 1864 mayfly
specimens from "parcel" 64 and 79
Ephemeropsis melanurus n. sp. Cockerell 1924 mayfly
 Odonata -
? Cymatophlebia mongolica n. sp. Cockerell 1924 true dragonfly
2 specimens from "parcel" 64 and 1 from 79
 Diptera - Chaoboridae
"Chironomopsis gobiensis n. sp." = Chironomaptera gobiensis
"Chironomopsis gobiensis n. sp." = Chironomaptera gobiensis Cockerell 1924 phantom midge
several specimens
 Trichoptera -
Trichopterella torta n. gen. n. sp.
Trichopterella torta n. gen. n. sp. Cockerell 1924 caddisfly
specimen from "parcel" 64
 Trichoptera - Limnephilidae
Indusia reisi n. sp. Cockerell 1924 caddisfly
 Dicondylia -
Coleoptera indet. Linnaeus 1758 beetle
3 specimens of poorly preserved beetles
 Ginkgoales - Ginkgoaceae
 Czekanowskiales -
Czekanowskia sp. Heer 1876
  - Phyllocladineae
Phyllocladites morrisi Cockerell 1924