Premise: Eucommia jeffersonensis is an extinct species of flowering plant in the family Eucommiaceae. It is known from a fossil fruit found in latest Eocene deposits of Oregon, United States. "E. jeffersonensis" is one of five described fossil species from North America assigned to the modern genus "Eucommia". The other species are "E. constans", "E. eocenica", "E. montana", and "E. rolandii".
Hypothesis: E. constans are related to E. jeffersonensis.