Diversity, phylogeny and biogeography of the South American ‘cardiomyine’ rodents (Hystricognathi, Cavioidea) with a description of two new species

Abstract

‘Cardiomyine’ rodents are extinct large terrestrial Caviidae closely related to capybaras, that inhabited large parts of South America during the middle Miocene and Pliocene. They are mostly preserved as isolated teeth, but also as skull and jaw fragments. Here we revise the taxonomy of this group and describe two new species, each pertaining to one of the two main late Miocene groups, represented by the genera Caviodon and Cardiomys. This suggests that the diversity of ‘cardiomyines’ was higher than previously thought. Among the specimens studied there are two almost complete skulls; one from the Andalhuala Formation, Catamarca, and the other from the Arroyo Chasicó Formation, Buenos Aires. The first, housed in the Field Museum of Natural History, was originally catalogued as Cardiomys ameghinorum, a common species for the late Miocene of north‐western Argentina (NOA), but is here transferred to the genus Caviodon. This is the first mention of the genus for NOA, enlarging its geographical distribution for the late Miocene. The second skull, assigned to Cardiomys sp., is housed in the Museo de La Plata. Furthermore, from the revision of the holotypes of the species of Caviodon (C. multiplicatus, C. bravardi, C. (Lelongia) paranensis, C. angustidens and C. scalai from the Conglomerado osífero of the Ituzaingó Formation; late Miocene, Argentina) we propose their synonymy with the type species C. multiplicatus, decreasing the specific diversity in that locality. Finally, our phylogenetic analysis indicates that the species of ‘cardiomyines’ are paraphyletic, placing them in a basal position among the Hydrochoerinae.

The Oldest Species of Dolichotis (Rodentia, Hystricognathi) from the Pliocene of Argentina: Redescription and Taxonomic Status of “Orthomyctera” chapalmalense

“…The work of Campo et al (2020) is really valuable and the molecular distance between the two extant species of maras is unquestionable. However, their study has an almost exclusively neontological focus and overlooks the fossil record and the great morphological diversity at the osteological level (at least in the cranium, mandible, and teeth) undergone by Cavioidea during the last 30 million years (e.g., Kraglievich 1932;Kramarz 2006;Pérez 2010;Pérez and Pol 2012;Vucetich et al 2015;Pérez et al , 2018Madozzo-Jaén 2019). Discrete morphological characters, despite the predominance of molecular datasets, continue playing an important role in inferring phylogenetic trees, even as the sole source of evidence for most fossil taxa.…”

“…However, it is interesting to note that in Miocene-Pliocene hydrochoerines, the M3 adds numerous posterior lobes/laminae (e.g., between four to more than 14; e.g., Vucetich et al 2005;Deschamps et al 2013;Pérez et al 2018).…”

Paleobiology of the basal hydrochoerineCardiomysAmeghino, 1885 (Rodentia, Caviomorpha, late Miocene, South America) as inferred from its postcranial anatomy

“…Specimen MLP 29-IX-3-19 differs from the type of this species because the fourth prism of M3 is narrower than the third and the posterior projection is continuous with the fourth prism. The M3 of the specimen MLP 29-IX-3-19 is very similar in size and general morphology (number and relative size of prisms, depth of labial flexi) to that of the type of Cardiomys leufuensis , but differs from it in the morphology of the second prism, which has two labial flexi in MLP 29-IX-3-19 and a straight labial side in C. leufuensis (Pérez et al, 2017a, fig. 6F).…”