Near the mouth of Hell Canyon, about 17 km ENE of Edgemont (OMNH V1243) (Cretaceous to of the United States)

Where: Fall River County, South Dakota (43.3° N, 103.6° W: paleocoordinates 39.9° N, 51.8° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Chilson Member (Lakota Formation), Late/Upper Berriasian to Late/Upper Berriasian (145.0 - 136.4 Ma)

• OMNH locality V1243 lies in the lower one-fourth of unit 2 of the Chilson Member

•(Micropaleontological) Age constraints for this part of the section, and therefore for OMNH locality V1243, are late Berriasian–Valanginian

Environment/lithology: fluvial; sandy mudstone and massive sandstone

• The Chilson Member has been subdivided into the informal units 1 and 2 by Post and Bell (1961), corresponding to fluvial unit 1 and fluvial unit 2 of Dahlstrom and Fox (1995: fig. 3), respectively
• The productive horizon, on a ledge between massive (and vertically exposed) sandstones, is a mudstone layer (ranging in thickness from 10–25 cm) with abundant indurated sandy lenses containing bone fragments and clayballs.

Size classes: mesofossils, microfossils

Collected by OMNH field parties in 2001–2003

Collection methods: bulk, sieve,

• OMNH, Sam Noble Oklahoma Museum of Geology

•The specimens described in this study were collected and prepared following standard methods of microvertebrate sampling detailed by Cifelli (1996).

Primary reference: R. L. Cifelli, B. M. Davis, and B. Sames. 2014. Earliest Cretaceous mammals from the western United States. Acta Palaeontologica Polonica 59(1):31-52 [R. Benson/R. Benson/J. Tennant]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 135449: authorized by Roger Benson, entered by Roger Benson on 26.10.2012, edited by Patricia Holroyd

Creative Commons license: CC BY (attribution)

Taxonomic list

• Other vertebrate groups are also represented in the OMNH collection from the Lakota Formation, including various chondrichthyans, osteichthyans, amphibians, lepidosaurs, crocodilians, and dinosaurs (to be described elsewhere).
unclassified
  -
Osteichthyes
 Temnospondyli - Albanerpetontidae
Albanerpetontidae indet. Fox and Naylor 1982 tetrapod
Mammalia
 Theriiformes - Dryolestidae
Lakotalestes luoi n. gen. n. sp.
Lakotalestes luoi n. gen. n. sp. Cifelli et al. 2014 mammal
Holotype OMNH 62673, right upper molar from the distal part of the series, perhaps M5
 Theriiformes - Spalacotheriidae
Infernolestes rougieri n. gen. n. sp.
Infernolestes rougieri n. gen. n. sp. Cifelli et al. 2014 mammal
Holotype OMNH 62671, right lower molar, perhaps m1
 Multituberculata -
Passumys angelli n. gen. n. sp.
Passumys angelli n. gen. n. sp. Cifelli et al. 2014 multituberculate
Holotype OMNH 64191, right m1
 Multituberculata - Plagiaulacidae
Bolodon hydei n. sp. Cifelli et al. 2014 multituberculate
Holotype OMNH 62670, a right M2