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

Abstract

The Subfamily Dolichotinae comprises two living species, Dolichotis patagonum, an emblematic component of the Patagonian fauna of Argentina, and Dolichotis salinicola, endemic to the Chaco ecoregion. These two species are also considered as pertaining to different genera, D. patagonum and Pediolagus salinicola. The oldest records of Dolichotis come from the Pliocene-Pleistocene boundary of northeastern and central Argentina, and the late Pleistocene from southern Brazil, and northern and southern Uruguay. Five fossil species were described from the Pleistocene and Holocene in central Argentina (D. minor, D. plathycephala, D. major, D. intermedia, and D. improla). "Orthomyctera" chapalmalense was described on the basis of remains from the coast of Mar del Plata and Chapadmalal, Buenos Aires Province, Chapadmalal Formation (late Pliocene, 3.74-3.04 Ma). A new detailed description of the holotype and its comparison with closely related taxa suggests that this species is more related to the genus Dolichotis, resulting in the new combination D. chapalmalense. The close affinities with Dolichotis revealed by phylogenetic analyses combined with molecular and morphological characters were corroborated in previous analyses. The origin of this lineage extends at least to a million years ago, taking the record back to the middle Pliocene. The evolutionary novelties that appear at least since the Pliocene, marking a key period for the Caviidae, are analyzed. Based on a phylogenetic perspective with the inclusion of the fossil record, our data support the inclusion of the two species (D. patagonum and D. salinicola) in a single genus.

Caviomorph rodents from the Pampean region (Argentina) in the historical Santiago Roth Collection in Switzerland

“…The genus Dolichotis encompasses two extant species: Dolichotis patagonum , from austral Argentina (Patagonia), and Dolichotis salinicola , from the Chaco ecoregion of Argentina, Paraguay, and Bolivia (Cabrera, 1961 ; Campos et al, 2001 ; Eisenberg & Redford, 1989 ; Madozzo-Jaén, 2019 ). The inclusion of both species in Dolichotis has been discussed over the years and recently confirmed by the comprehensive review by Madozzo-Jaén et al ( 2021 ), who employed cladistic analysis, including morphological data of extant and extinct data and molecular data to analyze the phylogenetic relationships of dolichotines. Other four Quaternary species ( D. platycephala , D. intermedia , D. major , and D. minor ) were recognized by Ameghino ( 1889 ) from central Argentina.…”

“…Other four Quaternary species ( D. platycephala , D. intermedia , D. major , and D. minor ) were recognized by Ameghino ( 1889 ) from central Argentina. However, according to Madozzo-Jaén et al ( 2021 ), these taxa were not studied after their original descriptions or other materials were not reported. Other Pleistocene records of Dolichotis are scarce and mainly represented by specimens not confidently identified at specific level.…”

“…Several groups became extinct in this continent during the Late Miocene and Pliocene, possibly associated with drastic environmental and biotic changes (Vucetich et al, 1999 , 2015 ). In addition, during the Pliocene the fossil record is marked by the appearance of several fossils assigned to extant genera (e.g., Candela & Boinini, 2018; Madozzo-Jaén et al, 2021 ). Subsequently, during Pleistocene times, a significant part of the current caviomorph diversity was already established, at least at the generic level.…”

Redefining the Huayquerian Stage (Upper Miocene to Lower Pliocene) of the South American chronostratigraphic scale based on biostratigraphical analyses and geochronological dating

“…2019; Madozzo‐Jaén et al . 2021). In turn, the genus Thylamys is known from the Middle Miocene of the Neotropics, La Venta, Colombia (Goin 1997) and Juan Guerra (TAR 31 locality), Peru (Stutz et al .…”

Systematic revision of Neoreomys huilensis Fields, 1957 (Rodentia, Hystricognathi) from the Middle Miocene of La Venta (Villavieja, Colombia)

“…The affinities of Neoreomys huilensis within Cavioidea are tested using a modified version of the combined dataset from Pérez & Pol (2012) and Madozzo-Jaén et al (2021). The modifications consist of the inclusion of two taxa: Neoreomys pinturensis and Neoreomys huilensis .…”