Scytalopus urubambae

Treated as a subspecies by Peters Vol.7 p.287. Elevated to species level by Krabbe and Schulenberg Remsen, 1998

Xenoperdix udzungwensis

Not in Peters, or {Sibley and Monroe, 1990}.

Centropus unirufus 1862

Peters Checklist Vol.4 p.76 lists 1863. {Richmond, et al. 1992} lists 1862 and notes the signature is dated "24 December 1862".

Pitta ussheri

Norbert Bahr writes (00.04.14): In his monograph on pittas and broadbills, Lambert (1996) [...] split Pitta ussheri from P. granatina. Based on based on parapatry and lacking evidence of hybridization.

Pseudoseisura unirufa

Treated by Peters Checklist vol.7 p.122 as a subspecies.
Zimmer & Whittaker. 2000. "The Rufous Cacholote is Two Species." Condor 102 (409-422) present behavioural and vocalization evidence for splitting the species.

Urocynchramidae Systematics

Groff JG. 2000. Molecular evidence for the systematic position of Urocynchramus pylzowi. Auk 117:787-791 discusses the systematics of this bird. He follows Domeniewski (1918) and Wolters (1979) in suggesting a family for this bird. He argues that it represents "a relict member of a lineage as old as, or older than, other families of finches."

I have tentatively placed it before the Fringillidae.

Phyllomyias urichi

See Cardoso da Silva JM, New data support the specific status of Reiser's Tyrannulet, a central Brazilian endemic. 1996. BBOC 116(2):109-113.

Cardoso da Silva argues that the number of unique diagnostic characters (ref. Stotz DF, The taxonomic status of Phyllomias reiseri. 1990. BBOC 110:184-187. and its separation from it's relatives by enormous distance suggest it should be treated as a distinct species.

Urotriorchis Systematics

Previously placed close to Accipiter, and sometimes merged in it.
However, Mlikovsky's study of osteology shows "Urotriorchis differs from Accipiter in a number of osteological characters and agrees in them with the Polemaetus group of eagles." Coracoid, scapular, furcular, and sternal features are discussed. Most significantly, a character of ungual phalanges is unique to the claws of Urotriochis, Polemaetus, Spizaetus, Spizastur, and Lophaetus.
In this character state there is a "broad, well developed and elevated facet postero-dorsally to the articular surface" of the phalanx.
Oroaetus isidori was not examined in that study.

Mlikovsky, J. 1999. "Note on the osteology and taxonomic position of African Long-tailed Hawk Urotriorchis macrourus (Aves: Accipitridae)". BBOC 119(1): 32-37.

Thanks to Normand David for bringing this to my attention.