Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird.

AGNOLIN, FEDERICO L.; VARRICCHIO, DAVID

GEODIVERSITAS

PUBLICATIONS SCIENTIFIQUES DU MUSEUM

Lugar: Paris; Año: 2012

1280-9659

Varricchio (2002) described some forelimb bones from the Late Cretaceous(Campanian) Two Medicine Formation, Glacier County, Montana (USA), asthe holotype of Piksi barbarulna, a supposed ornithothoracine bird. Howeverreevaluation of Piksi Varricchio, 2002 instead recognizes this genus as belongingto Pterosauria Kaup, 1834 and not Aves Linnaeus, 1758. Piksi exhibits thefollowing derived humeral traits of pterosaurs: 1) very large ectepicondyle; 2)large trochlea; 3) with a deep, wide and poorly deliminated brachial depressionthat is proximodistally extended; 4) a wide and deep olecranal fossa not markeddorsally by a ridge; and 5) lacking a distal depression of the groove for the m. humerotricipitalis.Moreover, the putative Early Cretaceous birds EurolimnornisJurcsák & Kessler, 1986 and Palaeocursornis Jurcsák & Kessler, 1986, based ondistal humeri, are also regarded as pterosaurs. The record of Piksi constitutes animportant addition to the Latest Cretaceous pterosaurian record.