A well-preserved second trogon skeleton (Aves, Trogonidae) from the middle Eocene of Messel, Germany

摘要

A second skeleton of a trogon is reported from the middle Eocene of Messel in Germany, which represents the best preserved Eocene record of this group of birds known to date. The new specimen shows that the Messel trogon, which was originally described as ?Primotrogon pumilio, differs from Primotrogon in a narrower spatium intermetacarpale of the carpometacarpus and a proportionally longer hallux. The middle Eocene species is thus assigned to the new taxon Masillatrogon. The plesiomorphically narrow spatium intermetacarpale supports a position of Masillatrogon outside a clade including Primotrogon and crown group Trogoniformes, and the presence of successive sister taxa of extant Trogonidae in the Paleogene and early Neogene of Europe indicates an Old World origin of the crown group. Masillatrogon and Primotrogon further lack derived features of the wing skeleton of extant Trogonidae, and these early trogons thus probably employed a somewhat different flight and foraging technique.