Avian footprints from the Upper Cretaceous Lecho Formation, Northwestern Argentina.

COPPA VIGGLIOCO, A.; ASTINI R.A.; DEGRANJE, F.; GOMEZ, F.J.

Buenos Aires

Congreso; Reunión Virtual Comunicaciones de la Asociación Argentina de Paleontología; 2021

Asociación Argentina de Paleontología

Avian footprints from the Upper Cretaceous Lecho Formation, Jujuy province, northwestern Argentina, are here reported. The fossils were recovered from the Campañan to Maastrichtian calcareous siltstones, sandstones and limestones immediately underlying the Yacoraite Formationat 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 casts, accompanied by others, partially preserved. 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 not 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 resemble the ichnogenus Alaripeda or Gruipeda. In the Lecho Formation, bird footprints are virtually unknown, in contrast with the overlying Yacoraite Formation that records Maastrichtian shorebirds ichnofacies in several sections of the studied area.