Octodontoids (Hystricognathi, Rodentia, Mammalia) from Pampa Castillo, Chile, and how rodents inform early Miocene South American biochronology

Caviomorph rodents were diverse and abundant components of South American
mammal communities since the late Eocene. Augmenting this diversity, we
describe the octodontoids of Pampa Castillo, an early Miocene site from
the Galera Formation in southern Chile (Aysén Region). Six genera and
eight 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
SALMA, consistent with previous studies. We conducted similarity analyses
on eleven early–middle Miocene Patagonian rodent faunas using hierarchical
clustering. Faunas generally fell within the three South American Land
Mammal ‘Ages’ (SALMAs) to which they were traditionally assigned:
Colhuehuapian, Santacrucian, and ‘post-Santacrucian’. The ‘Pinturan’ is a
proposed biochronologic interval between the Colhuehuapian and
Santacrucian. At the generic 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 rodent taxon distributions, reflecting complex
temporal and paleoenvironmental influences. Geochronologic 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 biochronologic interval, but that the differences between it and
‘typical’ Santacrucian faunas are attributable to geographic or
paleoenvironmental differences.