AVIAN FOOTPRINTS FROM THE UPPER CRETACEOUS LECHO FORMATION, NORTHWESTERN ARGENTINA

ARIADNA COPPA VIGLIOCCO; RICARDO A. ASTINI; FEDERICO DEGRANGE; FERNANDO J. GOMEZ

Reunión Virtual

Conferencia; Reunión Virtual Comunicaciones APA; 2021

Asociación Argentina de Paleontología

ABSTRACT: Avian footprints from the Upper Cretaceous Lecho Formation, Jujuy province, northwestern Argentina, are here reported. The fossils were recovered from the Campanian calcareous siltstones, sandstones and limestones immediately below the Yacoraite limestones at Jueya creek, about 7 km to the north of Tilcara town. At least two nearly complete footprints are preserved as casts in a reddish fine-grained sandstone slab, accompanied by others, partially preserved. The ichnofossils consist of two tetradactyl footprints, with an anisodactyl toe arrangement, placed side by side, resembling a resting behavior. The average length of the tracks is 60.9 mm while its average width is 48.4 mm. The digit impressions are thick, up to 8 mm wide; the well-developed hallux and digit III are curved inwards, and the remaining digits are not completely straight. The print of digit III is the longest, while those of digits II and IV are subequal in length. The average digit II?IV divarication angle print measures 133°. No webbing trace was observed. Based on the footprint morphology, the specimens closely resemble the ichnogenus Alaripeda or Gruipeda. In the Lecho Formation, bird footprints are virtually unknown, in contrast to the overlying Yacoraite Formation, which records similar Maastrichtian shorebirds ichnofacies in several sections of the studied area.