A new carinate bird from the late Cretaceous of Patagonia (Argentina). American Museum novitates ; no. 3323

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New York, NY : American Museum of Natural History
A new bird from the late Cretaceous of Patagonia (Argentina), known from associated wing elements, is described and its phylogenetic position evaluated. Fossil taxa as well as representatives of species of extant birds sampled from lineages considered to be basal within the crown clade were included in a cladistic analysis of 72 characters primarily from the thoracic limb. Based on the results of the phylogenetic analysis and identification of autapomorphies in the specimen, we name a new taxon Limenavis patagonica. Limenavis patagonica is identified as closer to the crown clade than Enantiornithes by the presence of three unambiguous synapomorphies: a fossa (sometimes with two distinguishable subparts) on the dorsal, distalmost extremity of the humerus; distal fusion of metacarpals II and III; and an extensor process on metacarpal I. It is placed closer to the crown clade than Ichthyornis, and, thus, unambiguously as a carinate (see Methods for terminology), by two further synapomorphies: the abruptly truncate contact of the dorsal trochlear surface of the ulna with the ulnar shaft and the loss of a tubercle adjacent to the tendinal groove on the distal ulna. Finally, Limenavis patagonica is diagnosed by three autapomorphies: the attachment of the pars ulnaris of the trochlea humeroulnaris on the proximal ulna developed as a pit-shaped fossa; the location of the pisiform process with its proximal surface at approximately the same level as the proximal surface of metacarpal I; and a scar of the ligamentum collaterale ventrale of the ulna proximodistally elongate and extending down the caudal margin of the brachial impression. Limenavis patagonica is placed just outside the avian crown clade. The shortest tree with the new taxon as part of the crown clade is five steps longer than the most parsimonious topology.
23 p. : ill., 1 map ; 26 cm.
Includes bibliographical references (p. 17-20).