COPROLITES IN THE NEOGENE OF NORTHWESTERN ARGENTINA

LUNA, CARLOS A.; ZURITA, ALFREDO E.; GALLI, CLAUDIA; LANDA RAMÍREZ, E.; ROBLEDO, JUAN M.; CONTRERAS, SILVINA A.; BÁEZ, JOHANNA; FARREL, E.; ZAMUDIO, B.; CANDELA, ADRIANA; ESCAMILLA, J.; ALONSO, R.

La Rioja

Simposio; VII Simposio del Mioceno - Pleistocenodel Centro y Norte de Argentina; 2023

Universidad Nacional de la Rioja

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