The evolutionary history of South American hystricognath rodents

VUCETICH, M.G.; VERZI, D.H.; DESCHAMPS, C.M.; OLIVARES, A.I.; PÉREZ, M.E.

Origins and Evolution of Cenozoic South American Mammals

Springer

Año: 2022;

Improvements in the knowledge of the temporal and geographic distribution of fossil caviomorph rodents, and on their systematics and phylogeny, allow tracing the major features of their evolutionary history. The fossil record shows that the splitting of most lineages of caviomorphs would have happened at least as early as the late Eocene. These lineages experienced their first important radiation in South America by the late Oligocene. After a subsequent period of relative stability (early Miocene to early-middle Miocene), the most important turnover in the history of caviomorphs occurred during the late-middle to late Miocene. It involved the evolution of several new families and subfamilies, the extinction of most of the ancient taxa, as well as a trend toward gigantism experienced in different lineages. This episode was part of a faunistic change recorded both worldwide and in southern South America, related to climatic change. The histories of the new families and subfamilies recorded in this late Miocene "modernization" phase are quite dissimilar, however. Fossils of the "Caviid" and Dinomyidae groups show they were already differentiated before their diversification in the Chasicoan. Modern Octodontidae, on the other hand, differentiated during the late Miocene, whereas Hydrochoeridae, Abrocomidae, "Eumysopinae" and Erethizontinae appeared suddenly as differentiated groups at that time.  Since the late-middle to late Miocene turnover, changes in caviomorph faunas were of lesser magnitude, with a gradual decrease in diversity in southern South America. However, an important pulse of extinction at the generic level occurred during the late Pleistocene-Holocene in intertropical areas, implying the extinction of ancient lineages. The record of Brazilian caviomorphs in the Quaternary of eastern Argentina supports this hypothesis.