Where: Japan (43.1° N, 143.7° E: paleocoordinates 47.3° N, 133.0° E)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Abathomphalus mayaroensis foram zone, Kawaruppu Formation, Late/Upper Maastrichtian (70.6 - 66.0 Ma)

• Diplomoceras cylindraceum, reported here, was extracted from a siltstone 15 m below the K/Pg boundary. Magnetostratigraphy at this site indicates that the base of C30r is situated 45 m below the K/Pg boundary (Hamano et al., 1986; Hamano, 1988; Kaiho, 1992). Using the time scale of Ogg (2012) for the geomagnetical polarity and Vandenberghe et al. (2012) for the K/Pg boundary, the age of the base of C30r is 68.369 Ma, and the age of the K/Pg boundary is 66.0 Ma. Supposing that the sediment accumulation rate is constant based on the monotonous siltstone throughout the sequence, the age of the fossil horizon is estimated to be ~66.8 Ma. D. cylindraceum, therefore, lived to at least ~0.8 m.y. before the K/Pg boundary event in the north Pacific region.

• bed-level stratigraphic resolution

Environment/lithology: marine; lithified siltstone

Size class: macrofossils

Collection methods: Repository: Historical Museum of Urahoro, Hokkaido, Japan

Primary reference: K. Kurihara, M. Kano, H. Sawamura and Y. Sato. 2016. The last surviving ammonoid at the end of the Cretaceous in the north Pacific region. Paleontological Research 20:116-120 [M. Clapham/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 177752: authorized by Matthew Clapham, entered by Matthew Clapham on 09.04.2016

Creative Commons license: CC BY (attribution)