4 - Phylogeny and evolutionary history of hystricognathous rodents from the Old World during the Tertiary: new insights into the emergence of modern “phiomorph” families

Summary

Introduction

The modern Afro-Asian porcupines, the African cane-, mole- and dassie-rats, as well as the South American guinea pigs, chinchillas, capybaras, pacas, agoutis, etc., make up the natural group of the hystricognathous rodents (infra-order Hystricognathi Tullberg, 1899). The phylogenetic relationships between the hystricognaths from South America (caviomorphs (Caviomorpha Wood, 1955)) and Africa (phiomorphs (Phiomorpha sensu Lavocat, 1967; Thryonomyoidea sensu Wood, 1955)) are today well-supported by a body of anatomical (e.g. Wood, 1974; Lavocat, 1976; Bugge, 1985; George, 1985; Meng, 1990; Luckett and Hartenberger, 1993; Martin, 1994) and molecular (e.g. Nedbal et al., 1996; Huchon and Douzery, 2001; Huchon et al., 2002, 2007; Poux et al., 2006; Montgelard et al., 2008; Blanga-Kanfi et al., 2009; Churakov et al., 2010) evidence, and also by endoparasite studies (e.g. Hugot, 1999). In contrast, the phylogenetic and geographic origins of hystricognaths have been the subject of considerable controversy over the past several decades (e.g. Wood and Patterson, 1959; Hoffstetter, 1972; Wood, 1972, 1973, 1974, 1985; Lavocat, 1973, 1974, 1976; Hussain et al., 1978; Flynn et al., 1986; Jaeger, 19; Huchon and Douzery, 2001, 2002; Marivaux et al., 2002, 2004; Jaeger et al., 2010a), and critical issues about their historical biogeography, notably their arrival in South America, are still a matter of on-going debate (e.g. Poux et al., 2006; Bandoni de Oliveira et al., 2009; Sallam et al., 2009, 2011; Coster et al., 2010; Antoine et al., 2012). Although hystricognaths are absent from the earliest Tertiary fossil record at a global scale, their earliest known fossil occurrences date back to the late middle Eocene from both Africa and South America. This either suggests that hystricognaths have rapidly achieved a widespread distribution throughout the Old and New Worlds just after their emergence, or points out the existence of a significant Eocene gap in their fossil record. During the late Eocene and early Oligocene, the group exhibited a high diversity and morphological disparity on both landmasses, thereby suggesting a considerable amount of undocumented diversity in their early evolutionary history.