Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum Vol. 52, No. 1

A new species of Macrocheira, M. enoptra from the Lookingglass Formation of Oregon, appears to be a smaller, younger individual than those from previously described extinct species. Fossil species of Macrocheira from west coastal North America fall into three categories: older, Eocene-Oligocene, strongly ornamented forms; younger, Oligocene-Miocene forms with subdued ornamentation; and the comparatively small form described here. Macrocheiridae is a small but well-represented family in the North Pacific from the Eocene through Holocene. Ontogenetic changes in carapace shape and ornamentation are observable in both extinct and extant species of Macrocheira.