Caviomorphs (Rodentia, Hystricognathi) from Pampa Castillo, Chile: new octodontoid records and biochronological implications

Abstract

Caviomorph rodents have been diverse and abundant components of South American mammal communities since the late Eocene. We describe herein the octodontoids of Pampa Castillo, a Lower Miocene site in southern Chile (Aysén Region). Six genera and seven species of octodontoids are present, two of which are new: Dudumus berggreni sp. nov. and Caviocricetus guenekko sp. nov. The octodontoids from Pampa Castillo support assignment of this fauna to the Santacrucian South American Land Mammal Age (SALMA), which is consistent with previous studies. We conducted similarity analyses on 11 Early–Middle Miocene Patagonian rodent faunas using hierarchical clustering. Faunas generally fell into the three SALMAs to which they were traditionally assigned: Colhuehuapian, Santacrucian and ‘post‐Santacrucian’. The ‘Pinturan’ is a proposed biochronological interval between the Colhuehuapian and Santacrucian. At the genus level, Pampa Castillo clustered with ‘Pinturan’ faunas, while at the species level it clustered with the ‘typical’ faunas on which the Santacrucian SALMA is based (from outcrops of the Santa Cruz Formation along the Atlantic coast and Río Santa Cruz). The Pampa Castillo rodent fauna resembles both ‘Pinturan’ and ‘typical’ Santacrucian faunas in taxon distributions, reflecting complex temporal and palaeoenvironmental influences. Geochronological data indicate that some ‘Pinturan’ sites overlap temporally with Pampa Castillo and the upper Pinturas Formation, which both clustered with ‘typical’ Santacrucian faunas. These results indicate that the ‘Pinturan’ does not represent a distinct biochronological interval, but that the differences between it and ‘typical’ Santacrucian faunas are attributable to geographic or palaeoenvironmental differences.

Un Pueblo Olvidado Y Su Resurgimiento: Primeros Registros Fósiles Del Cenozoico De Cabo Raso (Chubut, Argentina) Y Sus Implicancias Paleobioestratigráficas

“…Por otra parte, no se hallaron en Cabo Raso mamíferos fósiles exclusivamente deseadenses que permitan suponer una edad más antigua, o la presencia de otra SALMA (como por ejemplo el caso de Cerro Bandera, ver Kramarz et al, 2015 y literatura allí citada). En general, las asociaciones faunísticas atribuibles a la SALMA Colhuehuapense están comparativamente menos representadas en el registro fósil que aquellas referibles Publicación Electrónica -2023 -Volumen 23(2): 146-163 a otras edades (Deseadense o PanSantacrucense sensuBostelmann et al, 2013), algo que puede explicarse en parte por la ausencia de sitios con faunas colhuehuapenses por fuera de la Patagonia argentina(Bostelmann et al, 2013) McGrath et al (2022McGrath et al ( , 2023. describieron varias especies de roedores de la localidad de Pampa Castillo (Chile), asignables al Mioceno Temprano o Mioceno Medio, aunque serían más jóvenes que la SALMA Colhuehuapense de Patagonia, quizás comparable con la SALMA Santacrucense.…”