See caption below.
Fossil leaf from the earliest Eocene
(~55.5 million years) of the
Bighorn Basin, Wyoming.
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Parvileguminophyllum Popwyo Rhus

Natural History Highlight

Mississippi to Montana: Plants Danced to Climate’s Quick Tune

Parvileguminophyllum1. Parvileguminophyllum coloradensis: This type of leaf (belonging to the bean family) is known from somewhat younger deposits in the Green River Formation of southern Wyoming, Colorado and Utah.  It has not previously been recovered from Paleocene or earliest Eocene rocks in northern Wyoming or Montana. (Click here for full resolution.)

Popwyo2. Populus wyomingiana: Although this kind of fossil leaf has been formally described as belonging to the genus that includes living poplar trees, it has features that suggest is likely to belong to the family Euphorbiaceae, which has thousands of living species including poinsettia.  Populus wyomingiana is another leaf type commonly found in southern Wyoming during the warm period of the late early Eocene, as well as in the PETM deposits of northern Wyoming. (Click here for full resolution.)

Rhus3. cf. Rhus nigricans: This is another fossil leaf type found in the PETM flora of the Bighorn Basin that is similar to a species from the Green River Formation of southern Wyoming.  Attribution to Rhus, the genus that includes living sumacs, is uncertain, but this fossil leaf probably does belong to the family Anacardiaceae. (Click here for full resolution.)