Articulated avian remains from the early Oligocene of Poland adds to our understanding of Passerine evolution

摘要

In total, less than 50 specimens of the Passeriformes are known from the Paleogene, which contrasts with the fact that now it is the largest and most diverse order of birds. The so far described fossils include only three nearly complete specimens, an articulated wing and legs, and a handful of isolated bones. This paper describes a new species and genus of a passerine bird the size of the extant Parus major, imprinted on a slab and a counter slab of the siliceous clayey shales of the Outer Carpathians in southeastern Poland, and dated to the Rupelian, early Oligocene (ca. 31 m.y.a.). It is one of the very few passerine specimens from the Paleogene with bones in articulation, and thus provides a window into the ancestral osteology of passeriforms, which is characterized by a mosaic of characters typical for extant Oscines and Suboscines. The bird shows a unique manus, with a relatively short carpometacarpus and cleaver-shaped phalanx proximalis digiti majoris. Besides bones, fragmentary feathers are also imprinted on both slabs.