Triassic megaherbivore communal latrines: evidence of social behaviour and herbivory in dicynodonts

LUCAS FIORELLI; JULIA DESOJO; MARTÍN EZCURRA; MARTÍN HECHENLEITNER; ELOISA ARGAÑARAZ; JEREMÍAS TABORDA; BELÉN VON BACZKO; JIMENA TROTTEYN; AGUSTINA LECUONA

La Rioja

Jornada; Jornadas Argentinas de Paleontología de Vertebrados; 2013

Communal defecation latrines or ?dung piles? are a common behaviour in extant mammal megaherbivores such as rhinoceros, horses, tapirs, elephants, antelopes, and camelids. ˆis behaviour has important social functions as well as biological and ecological consequences for thespecies, plant populations and vegetation dynamics. Communal latrines of mammal megaherbivores are extremely rare in the fossil record and currently unknown among non-mammal fossil vertebrates. Here we report the discovery of several fossil communal latrines with copiousamounts of coprolites from the Middle Triassic lower lithological unit (Top Ten locality) of the Chañares Formation in La Rioja Province, Argentina. Thˆe characteristics of the communal latrines and the multiplicity, density, and morphology of thousands of in situ coprolites sugges that they belonged to gregarious species with a complex social behaviour comparable to that of extant megaherbivores. ˆe communal latrine surfaces range from 400 to 900 m2 and have an average density of 60 coprolites/m2. ˆe latrines are separated ~1500 meters from each other. Several lines of evidence ?such as the size of coprolites (c. 0.5 to 30 cm), density, and presence of plant microfragments within the coprolites and their association at the same level with juvenile and adult kannemeyeriiform dicynodonts? suggest that large dicynodonts (>2 m long) could have been the producers of the latrines. ˆe abundant coprolite associations described here are the "rst record of communal latrines in dicynodonts and non-mammal fossil vertebrates. ˆis behaviour matching that observed in extant megaherbivore mammals predates by over 200 million years the oldest known record.