Avian footprints from the Upper Cretaceous Lecho Formation, northwestern Argentina

COPPA VIGLIOCCO, A.; GÓMEZ, F.J.; ASTINI, R.A.; DEGRANGE, F.J.

Congreso; 1ra. Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina (RVCAPA); 2020

Asociación Paleontológica Argentina

Avian footprints from the Upper Cretaceous Lecho Formation, Jujuy province, northwestern Argentina, are here reported. The fossils were recovered from the Maastrichtian calcareous siltstones, sandstones and limestones of the uppermost interval of the unit at Jueya creek, about 7 km to the north of Tilcara town. At least two nearly complete footprints are preserved in a reddish fine-grained sandstone slab as a biogenic base structures, accompanied by others partially preserved ones. The ichnofossils correspond to two tetradactyl footprints, with an anisodactyl toe arrangement, placed side by side, resembling a resting behavior. The length of the tracks average is 60.9 mm while the footprints width average is 48.4 mm. The digit impressions are thick, up to 8 mm wide; the well-developed hallux and digit III are curved inwards, although remaining digits are no completely straight. The digit III is the longest print, while digits II and IV are subequal in length. The average digit II?IV divarication angle measured is 133°. No webbing trace was observed. Based on the footprint morphology, the specimens more closely resembles the ichnogenus Alaripeda or Gruipeda. In the Lecho Formation, bird footprints are virtually unknown, in contrast with the overlying Yacoraite Formation which records Maastrichtian shorebirds ichnofacies in several sections of the studied area.