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

FIORELLI, L.E.; DESOJO, J.B.; EZCURRA, M.D.; HECHENLEITNER, E.M.; ARGAÑARAZ, E. ; TABORDA, J.R.A.; VON BACZKO, M.B.; TROTTEYN, M.J.; LECUONA, A.

La Rioja

Jornada; XXVII Jornadas Argentinas de Paleontología de Vertebrados; 2013

CRILAR

Communal defecation latrines or "dung piles" are a common behaviour in extant mammalmegaherbivores, such as rhinoceros, horses, tapirs, elephants, antelopes, and camelids. Thisbehaviour has important social functions as well as biological and ecological consequencesfor the species, plant populations and vegetation dynamics. Communal latrines of mammalmegaherbivores are extremely rare in the fossil record and currently unknown among nonmammal fossil vertebrates. Here we report the discovery of several fossil communallatrines with copious amounts of coprolites from the Middle Triassic lower lithological unit(Top Ten locality) of the Chañares Formation of the La Rioja Province, Argentina. Thecharacteristics of the communal latrines and the multiplicity, density, and morphology ofthousands in situ coprolites suggest that belonged to gregarious species with a complexsocial behaviour comparable to that of extant megaherbivores. The communal latrinesurfaces range from 400 to 900 m2 and have an average density of 70 coprolites/m2. Thelatrines are separated around 1500 meters from each other. Several lines of evidencesuggest that large dicynodonts (>2 m long) should have been the producers of the latrines,such as the size of coprolites (ca. 0.5 to 30 cm), density, and presence of plantmicrofragments within the coprolites and their association at the same level with juvenileand adult kannemeyeriiform dicynodonts. The abundant coprolite associations describedhere are the first record of communal latrines in dicynodonts and non-mammal fossilvertebrates; this behaviour that matched that observed in extant megaherbivore mammalspredates the oldest record over 200 million years.