Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence

Abstract

Here we describe an unusual fossil assemblage found inside a crotovine from the late Pliocene Chapadmalal ‘Formation’ (Buenos Aires Province). This assemblage contains the greatest vertebrate diversity recovered inside an ichnofossil of this type, including skeletal remains of dasypodids, didelphids, procyonids, anurans and caviomorph rodents within coprolites and disaggregated scatological waste. We describe four general size types for crotovines and palaeoburrows found in the Pliocene to Holocene of Argentina and Brazil, of which the structure found corresponds to the ‘mid-large’ size type and is linked to the activity of the large dasypodid Ringueletia simpsoni. The scatological remains are assigned to a small-sized carnivorous mammal with a body mass of between 1 and 6 kg. Within the guild of Chapadmalalan omnivorous–carnivorous mammals, this inferred mass range is restricted to large didelphids and mid-sized procyonids (represented in the assemblage by Thylophorops chapadmalensis and Cyonasua lutaria, respectively). The data gathered here confirms that the reoccupation of burrows is a common behaviour in small-sized carnivorous mammals at least since the early Pliocene. In addition, we suggest a predator–prey relationship between the studied carnivores and the most abundant small fossorial mammals of the Pampean Pliocene.