Middle Pleistocene revelations: unravelling taphonomic processes in mammals including Mesotherium cristatum (Mesotheriidae, Notoungulata), Corralito Site, Córdoba Province, Argentina

Abstract

Taphonomic studies of Cenozoic mammals are scarce. We report a study of the taphonomy of the Corralito site (Middle Pleistocene to Holocene), Córdoba Province, Argentina, which documents the last population of the South American native ungulate typotherid Mesotherium cristatum. We discovered two specimens of M. cristatum (a hemimandible and postcranial remains) with numerous traces, along with one indeterminate camelid metapodial. Extensive and detailed analysis of these traces using macroscopic and confocal laser scanning microscopy has allowed us to identify various taphonomic agents: carnivoran bite traces, rodent gnawing, trampling, and root etching. We document the ichnotaxa Machichnus and Nihilichus and describe Corralitoichnus conicetensis gen. et sp. nov., which are attributed to Ctenomys incisors, along with Katagmichnus myelus gen. et sp. nov., associated with deep transverse traces on long bones diaphysis linked to bone breakage and marrow consumption by a medium–large carnivoran. This represents the first evidence of such behaviour in South America during the Cenozoic. Furthermore, the taphonomic time sequence of each recognized biological agent was reconstructed using a comprehensive understanding of the different biological processes that affected the specimens from post-mortem to post-burial. This study offers direct evidence of distinct biological agents from the Middle Pleistocene, particularly in the western Pampean region, focusing on one of South America's most iconic mammals (M. cristatum). It establishes a solid foundation for future taphonomic research on fossil bones, especially on predation or scavenging traces (Family Machichnidae), a relatively understudied area in South American native ungulates and the continent as a whole.