Baculites baculus

Taxon: Baculites baculus Meek and Hayden
Locality: Jefferson County, CO
Age: Cretaceous Period, Lower Maastrichtian Stage
Rock unit: Baculites baculus zone of Pierre Shale (of course)
Collector: N. Itano

Baculites was an uncoiled ammonite. Fragments of its shells, like this one, are very common in the Pierre Shale. Occasionally, a nearly complete shell is found. The various species are distinguished by their suture patterns, cross-sectional shapes, degree of taper, size, and surface ornament. The book by N. F. Larson et al., which is cited on the main Pierre Shale page, has a key for distinguishing between 24 species of Baculites found in the Pierre Shale. The suture pattern, which is somewhat simpler than, for example, that of Baculites scotti, and wide lateral ribs are distinguishing features of Baculites baculus. This specimen has been donated to the Science Department of Southern Hills Middle School, Boulder, Colorado. (Length 18 cm.)

For a closer look at the suture pattern, click here (11 kb).

A more complete specimen of a Baculites from the "Worldwide Museum of Natural History," still lacking part of the narrow end, can be seen here.

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Last modified: January 1, 1999. Send comments to