New specimens of the Eocene Messelirrisoridae (Aves : Bucerotes), with comments on the preservation of uropygial gland waxes in fossil birds from Messel and the phylogenetic affinities of Bucerotes

摘要

Exceptionally well-preserved new specimens of the Messelirrisoridae (Aves: Bucerotes), which show previously unknown features of the osteology and feathering of these tiny birds, are described from the Middle Eocene of Messel in Germany. Most notably in one of the new specimens the wing and tail feathers are excellently preserved and even show the former color pattern of the tail. A cream-colored substance in some specimens most likely constitutes fossilized uropygial gland waxes. For the first time, the phylogenetic affinities of the Messelirrisoridae are evaluated in a cladistic analysis, based on 122 characters and 34 extant and fossil taxa. The results of this analysis support the earlier hypothesis that Messelirrisoridae are stem lineage Upupiformes, i.e. the sister taxon of the clade including extant hoopoes (Upupidae) and woodhoopoes (Phoeniculidae). The analysis further supports sister group relationship between Bucerotes (Upupiformes + Bucerotidae [hornbills]) and Piciformes (woodpeckers and allies), although it is detailed that one of the recently proposed apomorphies of the clade (Bucerotes + Piciformes) is absent in the Messelirrisoridae.