Eocypselus rowei was named by Ksepka et al. (2013) [Eocypselus rowei differs from Eocypselus vincenti by (i) the stouter humerus (midshaft width equals approx. 20% total length for E. rowei versus 13% for the E. vincenti holotype), (ii) the presence of a rounded tubercle that projects ventrally from the body of metacarpal III near the contact with the trochlea carpalis and (iii) a proportionally shorter tarsometatarsus (tarsometatarsus length equals 50% of tibiotarsus length versus 54% for E. vincenti). The second character is not present in E. vincenti (fig. 6f of [16]) and other Pan-Apodiformes, and is considered an apomorphy of E. rowei. In comparing proportions, we note that the specimen is not badly crushed. Rather, it has been damaged by the splitting of the slab, so that several long bones are broken into two pieces exposing the internal surfaces. An expanded differential diagnosis is included in the electronic supplementary material.]. Its type specimen is WDC CGR-109, a skeleton (complete skeleton with intact feathering preserved as slab and counterslab), and it is a compression preserving soft parts. Its type locality is Lewis Ranch Site 2, which is in a Wasatchian terrestrial horizon in the Green River Formation of Wyoming.