Phylogeny and adaptive diversity of rodents of the family Ctenomyidae (Caviomorpha): delimiting lineages and genera in the fossil record

Abstract

Differentiation of genera of the modern (Late Miocene to Recent) South American rodent family Ctenomyidae would have been linked to the acquisition of disparate adaptations to digging and life underground. In accordance with this hypothesis, the delimitation of lineages and genera in the ctenomyid fossil record is evaluated here following an adaptation-rooted criterion that involves both an assessment of the monophyly and of the adaptive profiles of recognized clades. The application of such a criterion, including morphofunctional information, delimited four cohesive lineages among crown ctenomyids (i.e. euhypsodont species of the Late Miocene to Recent): Eucelophorus (Early Pliocene-Middle Pleistocene), Xenodontomys-Actenomys (Late Miocene-Pliocene), Praectenomys (Pliocene) and Ctenomys (including Paractenomys; Pliocene-Recent); in addition, the results supported the status of Xenodontomys as a paraphyletic ancestor of Actenomys. The cladogenesis that gave rise to the crown group would have occurred immediately after the acquisition of euhypsodonty in a Xenodontomys simpsonilike ancestor during the Late Miocene. This putative ancestor would have had fossorial habits and moderate digging specializations, an adaptive profile maintained in Xenodontomys-Actenomys. Eucelophorus and Ctenomys would have independently evolved subterranean habits at least since the Pliocene. Although the earliest history of the only living representative, Ctenomys, is known only fragmentarily, remains from Esquina Blanca (Uqu´ıa Formation), in north-western Argentina, suggest a minimum age of around 3.5 Ma (Early-Late Pliocene) for the differentiation of the genus. This date agrees with recent molecular estimates.

Late Cenozoic Vertebrates From the Southern Pampean Region: Systematic and Bio-Chronostratigraphic Update

“…Deposits of the Monte Hermoso Formation in its type locality Farola Monte Hermoso were accumulated in a dynamic fluvial environment of high-sinuosity rivers ("muddy fine-grained rivers" in Miall, 1985). In these localities, none of the species of Xenodontomys has been recorded, being instead abundant Actenomys priscus, the most derived representative of the lineage Xenodontomys-Actenomys (Verzi, 2008). In addition, when these specimens are compared to specimens of A. priscus found in levels assigned to the Chapadmalalan (from the area of Mar del Plata-Miramar), the latter display a more derived dental morphology (Deschamps, 2003;Tomassini et al, 2013a).…”

“…The first results were limited to specific localities (e.g., Quattrocchio et al, 1988;Deschamps and Borromei, 1992;Deschamps and Tonni, 1992;Verzi and Deschamps, 1996;Deschamps et al, 1998), but with time, data were used to make bio-chronostratigraphic proposals (Deschamps, 2003(Deschamps, , 2005, which were refined in subsequent papers (e.g., Verzi et al, 2004aVerzi et al, , 2008Deschamps et al, 2012Deschamps et al, , 2013Tomassini, 2012;Tomassini and Montalvo, 2013;Tomassini et al, 2013a) even making inferences about environmental conditions suggested by the recorded taxa. In this sense, rodents were particularly important among mammals (Verzi et al, 2004a;Quattrocchio et al, 2008;Deschamps et al, 2009Deschamps et al, , 2012Deschamps et al, , 2013Tomassini et al, 2013a;Vucetich et al, 2014aVucetich et al, ,b, 2015.…”

Chromosomes and speciation in tuco-tuco (Ctenomys, Hystricognathi, Rodentia)

“…В конце плиоцена они демонстрируют отчетливое уве-личение разнообразия, за которым следует вымирание всех родов за исключением рода Ctenomys. В плейстоцене наблюдается интенсивный кладогенез и значительная диверсификация тукотуко Verzi, 2008;Verzi et al, 2010).…”

Evolution of Brain Size in a Highly Diversifying Lineage of Subterranean Rodent Genus <i>Ctenomys</i> (Caviomorpha: Ctenomyidae)

“…Body size variation within the genus was most likely the result of selection pressures associated with the different habitats occupied by the approximately 56 living species [Vleck, 1979;Medina et al, 2007]. A distinctive characteristic of Ctenomys is that this genus has experienced an 'explosive' and relatively recent cladogenesis [Reig et al, 1990;Lessa and Cook, 1998;Verzi, 2008], posing the question of how brain size evolution tracked changes in body size. It was argued [Lande, 1979; see also Harvey and Bennett, 1983] that because direct selection on body weight does not seem to result in significant changes in brain weight, if closely related species are different mostly because of body size -for instance Ctenomys -their brain/body scaling coefficients would be expected to be lower than for species that are more distantly related, i.e., species within Caviomorpha in the present study.…”

“…This process, which took place during the Pleistocene, yielded more than 10 fossil species and at least 56 living species [Reig et al, 1990;Verzi, 2008]. Subterranean rodents such as Ctenomys have been described as those species that live in underground burrows and conduct the vast majority of their life underground [Lacey et al, 2000].…”