Morphological evidence for the taxonomic status of the Bridge’s Guan, Penelope bridgesi, with comments on the validity of P. obscura bronzina (Aves: Cracidae)

Penelope obscura Temminck, 1815 is a forest guan found in Brazil, Paraguay, Uruguay, Argentina and Bolivia. Three subspecies are currently recognized: Penelope o. obscura Temminck, 1815, P. o. bridgesi Gray, 1860, and P. o. bronzina Hellmayr, 1914. The limits between Penelope taxa are poorly understood since few studies have evaluated their differences in plumage, distribution and taxonomy. Based on 104 specimens deposited in ornithological collections we studied the variations in the plumage of P. obscura, including all characters that have been used to describe the included subspecies. Our results show that the plumage of these birds is extremely variable in southern and southeastern Brazil. Without any morphological and morphometric characters to support P. o. bronzina as a valid taxon, we synonymized it with P. obscura. Conversely, P. o. bridgesi, which occurs in the Yungas and the Chaco, is a distinct taxon and should be treated as a separate species from P. obscura.