ARTICLE Ontogenetic variability in the limb bones histology of plains vizcacha (Lagostomus maximus, Chinchillidae, Rodentia): implications for life history reconstruction of fossil representatives Mariana C. Garrone a , Ignacio A. Cerda b and Rodrigo L. Tomassini a a Instituto Geológico del Sur (INGEOSUR), Departamento de Geología, Universidad Nacional del Sur – CONICET, Bahía Blanca, Buenos Aires, Argentina; b Instituto de Investigación en Paleobiología y Geología (IIPG-CONICET), Universidad Nacional de Río Negro, Museo Provincial Carlos Ameghino, Cipolletti, Río Negro, Argentina ABSTRACT Osteohistological studies provide information on the life history of extant and extinct vertebrates, such as growth dynamics, age, body size, sexual maturity, sexual dimorphism, soft tissues, among others aspects. In this work, we evaluate the histological changes occurred during the ontogeny of extant representatives of plains vizcacha, Lagostomus maximus, through the analysis of limb bones in order to evaluate biological and ecological features of their life history. The results obtained are used as framework for the recognition of ontogenetic stages in isolated fossil limb bones of this species. The osteohistology clearly vary according to the ontogenetic stage of the individuals. It is described, for the first time, the presence of a neonatal line in rodents. We could identify different microstructural features that favor the correlation among extant and fossil representatives of L. maximus. It is considered that the mid-shaft of the humeri, femora and tibiae does not represent the most propitious sector to make the thin sections, since the modeling process there has erased part of the bone growth history of the individuals. This study contributes to the general knowledge of the bone histology of rodents. ARTICLE HISTORY Received 25 June 2019 Accepted 20 July 2019 KEYWORDS Mammal bone histology; chinchillids; life history; ontogenetic changes; fossorial habits Introduction Osteohistological studies constitute an important tool to elucidate biological traits of living and extinct taxa (Chinsamy-Turan 2005; Padian and Lamm 2013). This is possible since histological struc- tures have a common origin and meaning among vertebrates; which, in turn, allow inquire on processes and phenomena related to the life history of extinct species, such as growth dynamics, age, body size, sexual maturity, sexual dimorphism, soft tissue recon- struction, origin of bony structures and paleopathologies, among others (e.g. Reid 1996; Horner et al. 1999; Chinsamy-Turan 2005; Erickson 2005; Ehret 2007; Padian and Lamm 2013). In recent years, works focused on osteohistological analysis of living and fossil vertebrates are becoming more frequent. However, there are still a large number of taxa and topics that have not been addressed in detail. In this frame, rodents constitute a very small proportion of the osteohistological studies carried out on mammals (e.g. Enlow and Brown 1958; Geiger et al. 2013; Kolb et al. 2015a, 2015b; Orlandi- Oliveras et al. 2016; Montoya-Sanhueza and Chinsamy 2017, 2018). This situation is noteworthy, considering that this order represents 43% of the diversity of living mammal spe- cies, including taxa with clear differences in the body size, locomotor habits, diet and ecological niches, among other issues (Wilson and Reeder 2005), which has great potential for the development of biological studies. Caviomorph rodents constitute one of the most diverse groups of mammals in the Neotropical region, with wide ecomorphological variability (Geiger et al. 2013; Álvarez et al. 2017). Plains vizcacha, Lagostomus maximus Desmarest, 1817 (Chinchillidae, Lagostominae), is a large caviomorph -and the only living lagostomine- widely distrib- uted in the semi-arid grasslands and desert scrub of central and northern Argentina, southern Paraguay and southeastern Bolivia (Figure 1) (Hudson 1872; Branch et al. 1996; Jackson et al. 1996). It is a social species that forms groups of 10 to 30 members, including 1 to 3 adult dominant males, several adult females and immature individuals. These groups inhabit communal burrows systems, called ‘vizcacheras’ (Llanos and Crespo 1952; Branch 1993; Jackson et al. 1996). The repre- sentatives of this species have the ability to run at high speed and they are also good swimmers (Giulietti and Veneciano 2005). Lagostomus maximus exhibits a strong sexual dimorphism, in which males (weigh up to 9 kg) are larger and heavier than females (2.5–4.5 kg), and also have a more massive head and a more pronounced facial coloring pattern (Weir 1974; Jackson et al. 1996). There are also some differ- ences in the moment that occur sexual and skeletal (i.e. complete fusion of different portion/element of the skeleton) maturity; it was proposed that skeletal maturity occur between 12 to 16 months in females and 16 to 18 months in males, while sexual maturity occur from the eighth month in females and between 12 to 18 months in males (extending up to 30 months) (Jackson 1989, 1990; Branch et al. 1993). Remains of L. maximus are abundant in fossiliferous local- ities of the Late Pleistocene-Holocene of the Argentine CONTACT Mariana C. Garrone garrone.mariana@gmail.com Instituto Geológico del Sur (INGEOSUR), Departamento de Geología, Universidad Nacional del Sur – CONICET, Bahía Blanca, Buenos Aires 8000, Argentina HISTORICAL BIOLOGY https://doi.org/10.1080/08912963.2019.1648450 © 2019 Informa UK Limited, trading as Taylor & Francis Group Published online 01 Aug 2019