COPROLITES IN THE NEOGENE OF NORTHWESTERN ARGENTINA

LUNA, C.; ALFREDO E. ZURITA; CLAUDIA I. GALLI; ENZO M. LANDA RAMÍREZ; ROBLEDO, J. M; CONTRERAS, SILVINA A.; BAEZ, JOHANNA S.; FARRELL, E. E.; ZAMUDIO, M. B.; CANDELA, A.; ESCAMILLA, J.; RICARDO N. ALONSO

La Rioja

Simposio; VII SIMPOSIO MIOCENO ?PLEISTOCENO DEL CENTRO Y NORTE DE ARGENTINA; 2023

Museo de Ciencias Antropológicas y Naturales Universidad Nacional de La Rioja

Coprolites are an interesting ichnological proxies for the presence of animals in paleoecosystems. The morphology and composition of the coprolites can indicate body size, diet and other characteristics of the producer. The Palo Pintado Formation (Upper Miocene–earliest Pliocene) comprises fluvial system deposits under a subtropical to warm-temperate and humid climate, and constitutes one of the richest fossiliferous units in northwestern Argentina, with abundant vertebrate remains, including mammals, turtles, and caimans. In this contribution, the first record of coprolites for this unit is presented. The coprolites were recovered isolated, fragmentary, from different levels and can be divided into two morphotypes, one subcylindrical with flat basal surfaces, compact, with diameters between 18.2–24.6 mm, with subdivisions, coarsely conical at one end. The remaining are also cylindrical to subcylindrical, with larger diameters, between 25–35.4 mm, with constrictions due to peristaltic movements, and presence of external and internal porosity. In one of them, the presence of external moulds of some elements, preliminarily interpreted as seeds and other plant structures, has been observed. The morphology of these coprolites shows similarity with feces of large carnivores such as felids and canids, however in these there are usually remains belonging to the consumed prey. Other probable producers based on morphology are crocodilians, in which despite their carnivorous diet, remains of bones are not observed due to their complete digestion, and in addition, vegetal remains are usually recognized. Therefore, crocodilians seem to be the most probable producer of these structures, consistent with the paleontological record of the study area.