A 'snout' of Morenelaphus reveals unexpected phylogenetic relationships with old world cervids.

The Cervidae family constitutes the second most diverse family of Artiodactyla, besides Bovidae. During the Pleistocene, the Cervidae appeared in South America, coming from North America, as part of the Great American Biotic Exchange. Morenelaphus is possibly the most conspicuous cervid from the South American Pleistocene, as it has been recorded in many localities in the Pampas and Mesopotamian regions of Argentina, Uruguay, Paraguay and eastern Brazil. However, all its records are based on antlers and associated cranial fragments. Given this problem, there are still numerous anatomical aspects to know about Morenelaphus. We describe the most complete snout of a fossil deer in South America, assigned to Morenelaphus , found in late Pleistocene layers of the Pampas Region. We Ct-scan the specimen to describe its external and internal anatomy, measure and compare it with other living deer. We performed a phylogenetic analysis using a recent data matrix and including Morenelaphus for the first time. The results allow us to recognize new diagnostic traits of Morenelaphus and clearly separate it from other South American deer. Additionally, the phylogenetic analysis recognizes Morenelaphus as a member of Cervinae, as some previous authors have suggested. Our analysis has paleobiogeographic implications, since the recognition of a Cervinae in the Pleistocene of South America would imply that two lineages of Cervidae entered South America in the Pleistocene: The Cervinae and the Capreolinae. • Most complete Morenelaphus snout from Pleistocene of South America is described. • Phylogenetic analysis reveals new traits for Morenelaphus. • Morenelaphus is phylogenetically nested within Cervinae. • Cervinae probably arrived in South America before Odocoilinae. [ABSTRACT FROM AUTHOR]