USGS Mesozoic 19170, Forest Grove (Jurassic of the United States)

Where: Fergus County, Montana (47.0° N, 109.0° W: paleocoordinates 40.5° N, 50.6° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Gowericeras subitum ammonoid zone, Rierdon Formation (Ellis Group), Early/Lower Callovian (164.7 - 161.2 Ma)

• From lower 15 feet of Rierdon Formation

• group of beds-level stratigraphic resolution

Environment/lithology: marine; lithified lithology not reported

Size class: macrofossils

Preservation: mold/impression

Reposited in the USNM

Primary reference: B. Kummel. 1954. Jurassic nautiloids from western North America. Journal of Paleontology 28:320-324 [M. Clapham/M. Clapham/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 180713: authorized by Matthew Clapham, entered by Matthew Clapham on 29.07.2016

Creative Commons license: CC BY (attribution)

Taxonomic list

 Nautilida - Nautilidae
Eutrephoceras montanensis n. sp. Kummel 1954 nautiloid