Fossil Winged Walnut (Juglandaceae) Fruits - North Dakota

This is a pair of fossil fruits from the Juglandaceae (Walnut) family of the species Cyclocarya brownii. They are Late Paleocene in age from the Sentinel Butte Formation of North Dakota.

The walnut family of plants, Juglandaceae, includes walnuts, hickories, and pecans and has one of the best-documented fossil records in the northern hemisphere. The oldest modern genus, Cyclocarya, which is today restricted to a single extant species in China, first appears in the late Paleocene (57 million years ago) of North Dakota, USA. Unlike walnuts and pecans that produce edible fruits dispersed by mammals, Cyclocarya fruits are small nutlets surrounded by a prominent circular wing. Because of these wings, they might be assumed to be wind-disperse, but their radial symmetry does not have the aerodynamic qualities typical of wind-dispersed fruits, and may have been dispersed by water.

A paper describing these fruits in depth is linked below.

Cyclocarya brownii from the Paleocene of North Dakota, USA
Cyclocarya brownii
Morton County, North Dakota
Sentinel Butte Formation
1.1" wide fruits on 4 x 2.5" rock
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