Neornithine bird coracoid from the Upper Cretaceous

AGNOLIN, F.; NOVAS, F.; LIO, G.

AMEGHINIANA

Asociación Paleontológica Argentina

Lugar: Buenos Aires; Año: 2006 vol. 43 p. 245 - 248

0002-7014

Introduction The fossil record of Mesozoic neornithine birds is restricted to the Upper Cretaceous (Campanian, Maastrichtian) from America, Europe, Asia, and Antarctica (Hope, 2002). Most of the Cretaceous neornithines recorded at present, correspond to aquatic groups (e.g., Charadriiformes, Anseriformes; Olson and Parris, 1987; Elzanowski, 1995), but a few terrestrial forms were also documented (e.g., Psittaciformes, Galliformes, and probably Paleognathae; Stidham, 1998; Hope, 2002). This diversity of taxa constitutes the best available evidence to discuss the timing and branching sequence of clades of modern birds. With regard to the Mesozoic record of birds from South America, it is dominated by the Enantiornithes (Walker, 1981; Chiappe, 1996), an extinct group of worldwide distribution, considered to be the sister taxon of Ornithuromorpha (e.g., Patagopteryx plus Ornithurae; Chiappe, 2001). In contrast, the remains of Mesozoic neornithine birds in South America are restricted to a tarsometatarsus of the presumed loon (Gaviiformes) Neogaeornis wetzeli (Olson, 1992), from the Maastrichtian of Chile. The specimen here described consists of a partial coracoid, found in the Portezuelo Formation (Turonian-Coniacian, Late Cretaceous; Cruz et al., 1989; Leanza, 1999) of Sierra del Portezuelo, NW Patagonia (figure 1). Albeit fragmentary, the bone shows distinct neornithine features. The fossil was found in association with remains of pelecipods, turtle plates, and a number of appendicular bones and vertebrae pertaining to small-sized ornithopods, as well as teeth of dipnoans, crocodiles, sauropods, and non-avian theropods. A few meters above this fossiliferous level, several non-avian theropods were recovered: the alvarezsaurid Patagonykus puertai Novas, 1997, the bizarre tetanuran Megaraptor namunhuaiquii Novas, 1998, the basal dromaeosaurid Unenlagia comahuensis Novas and Puerta, 1997, and Neuquenraptor argentinus Novas and Pol, 2005. The present discovery enlarges our knowledge of the Late Cretaceous terrestrial faunas of Patagonia, but also adds relevant data about the timing and early radiation of neornithine birds.Patagopteryx plus Ornithurae; Chiappe, 2001). In contrast, the remains of Mesozoic neornithine birds in South America are restricted to a tarsometatarsus of the presumed loon (Gaviiformes) Neogaeornis wetzeli (Olson, 1992), from the Maastrichtian of Chile. The specimen here described consists of a partial coracoid, found in the Portezuelo Formation (Turonian-Coniacian, Late Cretaceous; Cruz et al., 1989; Leanza, 1999) of Sierra del Portezuelo, NW Patagonia (figure 1). Albeit fragmentary, the bone shows distinct neornithine features. The fossil was found in association with remains of pelecipods, turtle plates, and a number of appendicular bones and vertebrae pertaining to small-sized ornithopods, as well as teeth of dipnoans, crocodiles, sauropods, and non-avian theropods. A few meters above this fossiliferous level, several non-avian theropods were recovered: the alvarezsaurid Patagonykus puertai Novas, 1997, the bizarre tetanuran Megaraptor namunhuaiquii Novas, 1998, the basal dromaeosaurid Unenlagia comahuensis Novas and Puerta, 1997, and Neuquenraptor argentinus Novas and Pol, 2005. The present discovery enlarges our knowledge of the Late Cretaceous terrestrial faunas of Patagonia, but also adds relevant data about the timing and early radiation of neornithine birds.