Fossil and molecular evidence constrain scenarios for the early evolutionary and biogeographic history of hystricognathous rodents

Abstract

The early evolutionary and paleobiogeographic history of the diverse rodent clade Hystricognathi, which contains Hystricidae (Old World porcupines), Caviomorpha (the endemic South American rodents), and African Phiomorpha (cane rats, dassie rats, and blesmols) is of great interest to students of mammalian evolution, but remains poorly understood because of a poor early fossil record. Here we describe the oldest well-dated hystricognathous rodents from an earliest late Eocene (Ϸ37 Ma) fossil locality in the Fayum Depression of northern Egypt. These taxa exhibit a combination of primitive and derived features, the former shared with Asian ''baluchimyine'' rodents, and the latter shared with Oligocene phiomorphs and caviomorphs. Phylogenetic analysis incorporating morphological, temporal, geographic, and molecular information places the new taxa as successive sister groups of crown Hystricognathi, and supports an Asian origin for stem Hystricognathi and an Afro-Arabian origin for crown Hystricognathi, stem Hystricidae, and stem Caviomorpha. Molecular dating of early divergences within Hystricognathi, using a Bayesian ''relaxed clock'' approach and multiple fossil calibrations, suggests that the split between Hystricidae and the phiomorphcaviomorph clade occurred Ϸ39 Ma, and that phiomorphs and caviomorphs diverged Ϸ36 Ma. These results are remarkably congruent with our phylogenetic results and the fossil record of hystricognathous rodent evolution in Afro-Arabia and South America.

A new and primitive species of Protophiomys (Rodentia, Hystricognathi) from the late middle Eocene of Djebel el Kébar, Central Tunisia

“…From a paleontological perspective, hystricognaths are so far absent (unknown) from the earliest Tertiary fossil record at a global scale. Their earliest occurrences date only from the late middle or early late Eocene in both Africa and South America (Jaeger et al, 1985(Jaeger et al, , 2010aSallam et al, 2009;Antoine et al, 2012). Such a record either indicates the existence of a significant Eocene (Lutetian) gap in the hystricognath record, or suggests that this group achieved a rapid widespread distribution in the Old and New Worlds just after its emergence.…”

“…In this paper, we analyze the dental material of that rodent. These teeth document a diminutive and primitive new species of Protophiomys, a basal genus of hystricognathous rodents which is well known from Bir el Ater in eastern Algeria (Nementcha mountains: P. algeriensis; Jaeger et al, 1985), Birket Qarun 2 in Egypt (Fayum BQ-2: P. aegyptensis; Sallam et al, 2009), and possibly from Dur At-Talah in Libya (DT-Loc 1&2: "P." durattalahensis; Jaeger et al, 2010a; see discussion section), three mammalian-bearing localities very close in age at the end of the Eocene (latest middle [? ] to early late Eocene).…”

Two New Taxa (Caviomorpha, Rodentia) from the Early Oligocene Tinguiririca Fauna (Chile)

“…Early caviomorph biogeography: Gaudeamus, from Egypt, has recently been interpreted to represent a caviomorph, closely related either to Incamys (Coster et al, 2010;Antoine et al, 2011;Sallam et al, 2009Sallam et al, , 2011 or to Branisamys and Sallamys (Bertrand, 2009;Coster et al, 2010;Sallam et al, 2011). If Gaudeamus is truly nested within Caviomorpha and is not simply convergent upon isolated caviomorph taxa (such as being "taeniodont, " i.e., lacking a connection between the hypoconid and hypolophid and thus having a confluent metafossettid and hypoflexid, with fusion of the hypoflexus and the paraflexus on the upper molars), this would have obvious biogeographic implications.…”

“…The venerable notion of caviomorph monophyly (Wood and Patterson, 1959) has been corroborated repeatedly by molecular analyses (Nedbal et al, 1994;Huchon and Douzery, 2001;Opazo, 2005;Farwick et al, 2006;Poux et al, 2006;Huchon et al, 2007;Blanga-Kanfi et al, 2009;Churakov et al, 2010), but morphological evidence has remained more ambiguous. Auditory (Meng, 1990) and dental (Marivaux et al, 2004;Sallam et al, 2009) features have been interpreted as indicative of caviomorph monophyly, as has a recent combined molecular and morphological dataset (Horovitz et al, 2006). Nevertheless, a polyphyletic origin involving two independent colonizations has also been proposed on the basis of carotid arterial patterns and myology (Bugge, 1985;Woods and Hermanson, 1985;Bryant and McKenna, 1995;McKenna and Bell, 1998;Landry, 1999;Jenkins et al, 2005) and incisor enamel (Martin, 1994).…”

RNA-mediated degradation of microRNAs: A widespread viral strategy?

“…Squirrel monkeys and spider monkeys are both New world monkeys, and are thought to have shared a common ancestor around 20 Myr ago. 46 Thus, the approximate points when these 2 miR-27 degrading activities arose in the ancestry of MCVM and HVS can be mapped onto the herpesvirus phylogeny (Fig. 1).…”