This is the overview section on swan fossils (p. 159):

(Reproduced with permission from the Carnegie Institution.)

"Four species of swans were previously recorded from the Fossil Lake deposits. In addition, the type specimen of Anser condoni Shufeldt, a large furcula, is also undoubtedly swan. Only one specimen, the extinct Cygnus paloregonus, was recognized by Cope; Shufeldt added C. buccinator and C. columbianus, and described another species, C. matthewi, as well as the so-called goose, Anser condoni.

Among the 157 fossil bones of swans which have now been examined, but two species can be distinguished, and the record is therefore amended here to include only Cygnus buccinator and one extinct form. This results in the lumping of the species previously described as Cygnus paloregonus Cope (1878, type tarsometatarsi), Anser condoni Shufeldt (1892, type furcula), and Cygnus matthewi Shufeldt (1913, type carpometacarpi and scapulae). As paloregonus was first to be described, the other two now become synonyms of that species.

Regarding "Anser condoni," it is obvious that Shufeldt had no specimens of mute swan at the time he described the fossil species, and presumably knew nothing of the simplified structure of the furcula associated with the absence of looping of the trachea in some swans. The largest simple anseriform furcula available to him was that of a goose, hence the referral of the fossil furcula to the genus Anser.

The description of "Cygnus matthewi" was undoubtedly the result of Shufeldt’s misconception of the size of paloregonus. Apparently he had become convinced that this extinct species was larger than C. buccinator (see Shufeldt, 1913, p. 151, footnote). This interpretation was entirely at variance with Cope’s original description of the species, in which he said (1978, p. 388), "These tarsometatarsi indicate a species of the size of those now existing on this continent but different from them." Shufeldt (1913, p. 150), however, went so far as to discard the 3 most diagnostic of Cope’s type tarsi, and practically reconstructed a new paloregonus based on specimens larger than any Recent bones then available, but now recognized as belonging to C. buccinator. Having set aside these large (buccinator) bones as paloregonus, he found it necessary to describe another species (C. matthewi) to account for the bones of lesser size which, in certain elements, showed structural differences from modern C. buccinator and C. columbianus.

It is evident from the present study that the tarsometatarsi selected by Cope as the type specimen of C. paloregonus differ from both C. buccinator and C. columbianus in characters other than size, and are, therefore, valid representatives of an extinct species. It is also evident, as before stated, that the largest of the swan bones agree, both in structural details and in size, with Cygnus buccinator, and should be so assigned."