A new Pleistocene Ctenomys and divergence dating of the hyperdiverse South American rodent family Ctenomyidae
DE SANTI, NAHUEL A.; VERZI, DIEGO H.; OLIVARES, A. ITATÍ; PIÑERO, PEDRO; ALVAREZ, ALICIA; MORGAN, CECILIA C.
JOURNAL OF SYSTEMATIC PALAEONTOLOGY
CAMBRIDGE UNIV PRESS
Lugar: Cambridge; Año: 2021 vol. 19 p. 377 - 392
The South American Ctenomys is the most speciose genus among both hystricomorphs and subterranean rodents of theworld. Here, we present the most exhaustive phylogenies and timetree of living and extinct Ctenomys attempted thusfar. We describe Ctenomys rusconii sp. nov., a small-sized species from the upper Early Pleistocene of centralArgentina. We analyse its cranial and mandibular shape as well as its phylogenetic position in the context of otherextinct Ctenomys and a wide sample of living species. A parsimony analysis shows that Ctenomys rusconii sp. nov.integrates the stem group of Ctenomys together with late Pliocene to Middle Pleistocene species, while the crown groupcomprises only Middle Pleistocene to recent representatives. Within the crown Ctenomys, nine well-supported majorclades were recovered, eight of which are consistent with previously recognized extant species groups. A Bayesian tipdatinganalysis provided divergence age estimates of 3.8Ma and 1.3Ma for the origin of the genus and the crown clade,respectively. Remarkably, the extinct species recovered as members of the crown clade, i.e. C. dasseni, C. kraglievichi,C. subassentiens and C. viarapaensis, were clustered into the earliest diverging clade corresponding to the frater speciesgroup. Age estimates for the divergence of the crown and its major clades are markedly younger than what has beengenerally considered so far, which implies a new view on the timing of taxonomic, ecological and geographicaldiversification of the genus. Even considering that this interpretation is affected by biases inherent to the fossil record,the phylogenetic delimitation of the crown clade as restricted to species recorded since the Middle Pleistocene seems toconfigure a pattern underlain by a fast and late cladogenesis.