Incamys bolivianus was a caviomorph rodent representing an early member of the chinchillid family, with its closest modern relatives being chinchillas and viscachas.
Living in what is now Bolivia and Argentina during the late Oligocene about 27 million years ago, it inhabited an arid open grassland at a time when the area’s climate had drastically cooled due to the formation of the Antarctic Circumpolar Current.
It’s estimated to have been similar in size to a large modern chinchilla – weighing around 700g (~1lb 8oz) and measuring about 25-30cm long not including the tail (~10-12″).
An endocast of the shape of its brain from a near-complete fossil skull shows that it had a well-developed sense of hearing, particularly in vocalization processing, suggesting it may have been a social animal living in groups communicating with complex calls similar to modern chinchillids. It was probably a ground-dweller less agile than its modern relatives, but still capable of fast movements.
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