Burrow systems of modern subterranean rodents (Ctenomyidae): key neoichnologic features and recognition of fossil examples

Abstract

AbstractThis study is aimed to identify the distinctive ichnologic features of burrow systems of two ctenomyid species of extant solitary and subterranean rodents (Ctenomys azarae and C. talarum occidentalis) from La Pampa Province (Argentina). A total of 12 active burrows from different biogeographic provinces were cast with polyurethane foam, then excavated and the entire system was mapped. Ctenomyid burrow systems are shallow (average depth 0.30 m), branched, and subhorizontal with several plugged entrances, having a main tunnel and secondary ones arranged in a single level. Curved length, tortuosity, fractal dimension branching angles, and the scarcity or absence of chambers are similar in both species. The average horizontal diameter is 66 mm, the burrow cross-section is subcircular to vertical elliptical, and entrance ramps slope at an average of 22°. Surface ornamentation in the form of sets of three curved claw traces composing a chevron pattern is dominant. Ctenomys azarae is distinguished from C. talarum occidentalis by the presence of food caches and wider sets of claw traces. Ctenomyidae burrows are easily distinguished from those of Octodontidae and Caviidae using the relative diameter index. The outlined criteria are applied to identify fossil examples of Late Miocene-Holocene ctenomyid burrows.Keywords: Semi-arid environmentrodent burrowCtenomysburrow cross-sectionsurface ornamentationclaw tracesfossil tetrapod burrow AcknowledgmentsThis research is part of the doctoral thesis in Biology by MCC at the Universidad Nacional del Comahue (San Carlos de Bariloche, Río Negro Province, Argentina). Permission to work in the Gran Salitral area was granted by the Dirección de Recursos Naturales, Government of La Pampa Province. This work was funded by project PICT2019-114 from the Agencia Nacional de Promoción Científica y Tecnológica of Argentina and project G22 from Universidad Nacional de La Pampa to RNM. We especially thank Enrique Justo and family (owners of La Florida), Hugo Cerda (owner of Puesto La Porfía), and the Cobo family (from Naicó) for allowing us to work in their land and their hospitality. Marta Kin, Fátima Mendoza Belmontes, Luciana Cobo and Nahuel Espinoza are thanked for help during fieldwork.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by Agencia Nacional de Promoción Científica y Tecnológica [PICT2019-114] and Consejo Nacional de Investigaciones Científicas y Técnicas [PIP 2021-2023-146].