Neogene communal rodent burrow systems from central Argentina

ABSTRACT

Fossil tetrapod burrows from the Cerro Azul Formation (Late Miocene-Early Pliocene) of southwestern Buenos Aires Province, Argentina, are described and interpreted. The local sedimentary sequence is composed of massive siltstone, with two interbedded calcareous palaeosols, that were deposited in a loessic plain under a semiarid climate. The burrow systems are recognised as Maneraichnus pampeanum igen. and isp. nov., an ichnotaxon that is typified by long ramps that lead to a main chamber located at bifurcation, with chambers forming at least one-third of the total tunnel/ramp volume. A rodent producer is indicated by the presence of interconnected burrow systems with a subcircular cross-section (average RDI = 0.98) and by paired, blunt, incisor traces. The large ratio of chamber volume to tunnel/ramp volume (0.45) is indicative of a communal species and a body mass ranging from 0.9 to 4.6 kg is inferred for the producer. Considering the mentioned constrains and the fossorial mammals of the Cerro Azul Formation, it is proposed that the burrow systems belonged to Lagostomus (Late Miocene-Recent). The fossil burrows also match extant L. maximus (‘vizcacha’) burrow systems in overall architecture, passive fill, and similar size of claw traces. Miocene species of Paedotherium (Notoungulate) is discussed as an alternative potential digger.http://zoobank.org:act:C3588BE1-BAAF-46D7-92FA-0ADEF295AED3http://zoobank.org:act:2A9F3301-9EC8-4FD1-B875-078CD9324049

KEYWORDS:

• Mammal burrows
• ichnotaxonomy
• taphonomy
• Cerro Azul Formation
• Lagostomus
• Maneraichnus pampeanum

Acknowledgments

We are indebted to Marcelo Zárate for noticing about the fossil burrows of this locality, Rodrigo Tomassini and Renata Sostillo for the information provided, and Teresa Manera de Bianco and Florencia Cozzani for help during field work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2228319.

Additional information

Funding

This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica [PICT 2019 – 114]; Consejo Nacional de Investigaciones Científicas y Técnicas [PIP 2021–2023 146].