20 - Morphological disparity of the postcranial skeleton in rodents and its implications for palaeobiological inferences: the case of the extinct Theridomyidae (Rodentia, Mammalia)

Summary

Introduction

Rodents constitute roughly half of the current mammalian diversity. This astonishing specific diversity is shown most notably in terms of ecology as they occupy the majority of the ecosystems on the planet, from aquatic environments to desert areas. Current rodent diversity is the result of multiple radiations linked to the invasion of new ecological niches. The diverse rodent groups developed a wide locomotor repertoire, shown first and foremost by a morphological differentiation of the postcranial skeleton. Startlingly, rodents have not traditionally been the animal model of choice for investigating the evolution of the mammalian postcranial anatomy, probably because a great majority of extant species (murids in particular) are often depicted as “terrestrial generalists”. In comparison to the abundant literature on cranial and dental morphology, the rodent postcranial anatomy has received relatively little attention. Meanwhile, inconsistent terminology and imprecision in the definition of habitats, postural behaviors, feeding behaviors, locomotor repertoires (Table 20.1), which are often used interchangeably, have led to confusion.

The fossil record has only occasionally been considered and the extinct species under study often belong to families that still have existing representatives, like sciurids and murids (Vianey-Liaud, 1974; Emry and Thorington, 1982; Szalay, 1985; Price, 1993; Thorington and Darrow, 2000; Bover et al., 2010; Michaux et al., 2012), caviomorphs (Carrano, 1997; Elissamburu and Vizcaino, 2004; Weisbecker and Schmid, 2007; Candela and Picasso, 2008; Araújo et al., 2013), and castoroids (Samuels and Valkenburgh, 2008), although a few concern extinct rodent groups, such as paramyids (Wood, 1962; Szalay, 1985; Rose and Chinnery, 2004). Extinct rodents are mainly documented by isolated bones and finding complete skeletons remains a very rare event. Thus, reconstructing the life history of extinct rodents based on postcranial features seems tentative and extremely challenging. In this context, can palaeontologists contribute to efforts to better understand the evolution of the rodent postcranial anatomy?