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New Mesozoic bird papers in AMNH Novitates

From: Ben Creisler bh480@scn.org

New issues of American Museum of Natural History Novitates 
are available online. Two concern Mesozoic birds:

CLARKE, J.A. and M. A. NORELL, 2002. The Morphology and 
Phylogenetic Position of Apsaravis ukhaana from the Late 
Cretaceous of Mongolia.
American Museum Novitates: No. 3387, pp. 1-44.
 The avialan taxon Apsaravis ukhaana  from the Late 
Cretaceous of southern Mongolia is completely described 
and its phylogenetic position is evaluated. Apsaravis 
ukhaana  is from continental sandstones exposed at the 
locality of Ukhaa Tolgod, Omnogov Aimag, Mongolia. The 
holotype specimen consists of the nearly complete, 
articulated skeleton of a small volant avialan. 
 Apsaravis ukhaana  is unambiguously differentiated from 
other avialans based on the presence of several unique 
morphologies: a strong tubercle on the proximal humerus, a 
hypertrophied trochanteric crest on the femur, and 
extremely well-projected posterior wings of a surface of 
the distal tibiotarsus that in Aves articulates with the 
tibial cartilage. Ten other homoplastic characters 
optimize as autapomorphies of Apsaravis ukhaana  in the 
phylogenetic analysis. They are as follows: ossified 
mandibular symphysis; dentary strongly forked posteriorly; 
hooked acromion process on scapula; highly angled dorsal 
condyle of humerus; humeral condyles weakly defined; 
distal edge of humerus angling strongly ventrally; humerus 
flared dorsoventrally at its distal terminus; lateral 
condyle of tibiotarsus wider than medial one; neither 
condyle of tibiotarsus tapering toward the midline; and 
metatarsal II trochlea rounded rather than ginglymoid.
 Phylogenetic placement of Apsaravis ukhaana  as the 
sister taxon of Hesperornithes + Aves resulted from 
analysis of 202 characters scored for 17 avialan ingroup 
taxa. The implications of Apsaravis ukhaana ,and the 
results of the phylogenetic analysis, for the evolution of 
flight after its origin and character support for 
enantiornithine monophyly are extensively discussed.

KUROCHKIN, E.N., G.J. DYKE, and A. A. KARHU, 2002.
A New Presbyornithid Bird (Aves, Anseriformes) from the 
Late Cretaceous of Southern Mongolia.
American Museum Novitates: No. 3386, pp. 1-12.

 We describe a new large representative of the important 
fossil anseriform taxon Presbyornithidae from the latest 
Cretaceous (Maastrichtian) Nemegt Formation of southern 
Mongolia. This new taxon, Teviornis gobiensis.n. gen. et 
n. sp., is known from the associated manual portion of a 
right wing and the distal end of a right humerus, but is 
clearly diagnosable with respect to all other known 
representatives of the fossil Presbyornithidae. It is 
placed within the clades Anseriformes and 
Presbyornithidae, respectively, on the basis of a number 
of derived characters of the carpometacarpus and digits. 
Importantly, description of Teviornis confirms the 
presence of members of the neornithine clade Anseriformes 
(?waterfowl?) in the Late Cretaceous, as has been 
suggested previously on the basis of much less diagnostic 
fossil material as well as from clade divergence estimates 
founded on molecular sequence data. The extinct 
Presbyornithidae thus has a worldwide distribution and 
ranged in age from at least the Maastrichtian through to 
the uppermost Eocene.