See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/229939299 High-level phylogeny of early Tertiary rodents: Dental evidence Article in Zoological Journal of the Linnean Society · September 2004 DOI: 10.1111/j.1096-3642.2004.00131.x CITATIONS READS 148 304 3 authors: Laurent Marivaux Monique vianey-liaud Université de Montpellier Université de Montpellier 189 PUBLICATIONS 3,368 CITATIONS 197 PUBLICATIONS 3,024 CITATIONS SEE PROFILE SEE PROFILE Jaeger jean-jacques French National Centre for Scientific Research 331 PUBLICATIONS 9,283 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: South Asian mammals View project DEcline of ArtioDactyls ENDemic to EuRope (DEADENDER) View project All content following this page was uploaded by Laurent Marivaux on 15 January 2019. The user has requested enhancement of the downloaded file. Blackwell Science, LtdOxford, UKZOJZoological Journal of the Linnean Society0024-4082The Lin- nean Society of London, 2004? 2004 1421 105134 Original Article L. MARIVAUX ET AL. PHYLOGENY OF EARLY TERTIARY RODENTS Zoological Journal of the Linnean Society, 2004, 142, 105–134. With 7 figures High-level phylogeny of early Tertiary rodents: dental evidence LAURENT MARIVAUX*, MONIQUE VIANEY-LIAUD and JEAN-JACQUES JAEGER Institut des Sciences de l’Évolution, Laboratoire de Paléontologie, c.c. 64, Université Montpellier II, Place Eugène Bataillon, F-34095 Montpellier cedex 05, France Received February 2003; accepted for publication June 2004 Major crown-groups of rodents were well established in the early Tertiary, and fossils provide an invaluable window into their evolutionary history. The main focus of this project was to perform a cladistic assessment of the dental evi- dence for early Tertiary rodent cladogenesis – the masticatory apparatus and teeth are the most frequently preserved anatomical features in the fossil record. We focused on groups that existed in a period corresponding to their early history, combining fossils belonging to extinct lineages and to stem-groups leading to modern lineages. While the monophyly of some groups is not systematically explored, our results have important implications for high-level rodent relationships and systematics. These results are consistent with those of recent molecular phylogenies and reliably congruent with the stratigraphic record, thus enhancing the pertinence of dental characters for phylogenetic inference. Our approach provides evidence of a fundamental dichotomy in early rodent history. Two major clades have been identified: (1) the earliest ‘ctenodactyloid’ (Ctenodactylidae, Chapattimyidae, Yuomyidae, Diatomyidae) and hystricognathous (Tsaganomyidae, Baluchimyinae, ‘phiomorphs’, ‘caviomorphs’) rodents, and (2) the earliest ‘ischyromyoid’ rodents with their closest relatives (Muroidea + Dipodoidea + Geomyoidea + Anomaluroidea + Cas- toroidea + Sciuravidae + Gliroidea, and Sciuroidea + Aplodontoidea + Theridomorpha). This topology has led us to endorse Ctenohystrica as the first clade and propose a new taxon, Ischyromyiformes, for the second. Although min- imized in our working hypothesis, the homoplasy in dental characters remains significant. However, a number of homoplasic characters reveal structuring in their internal distribution, allowing us to discern evolutionary morpho- logical patterns, notably the pentalophodonty of molars, zygomasseteric complex and incisor enamel microstructure. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142, 105–134. ADDITIONAL KEYWORDS: cladistics – evolutionary potential – microstructure – morphology – Palaeogene – phylogeny – Rodentia – stratigraphy – structured homoplasy – systematics – teeth. INTRODUCTION and complete mitochondrial DNA sequence analyses (Graur et al., 1991; Li, Hide & Graur, 1992; D’Erchia The order Rodentia includes nearly one-half of all et al., 1996; Reyes et al., 1998, 2000). On the other modern species of Eutherian mammals (Wilson & hand, studies based on nuclear genes do support Reeder, 1993), having achieved almost worldwide monophyly (Huchon et al., 2000, 2002; Adkins et al., distribution since the end of the Palaeogene (e.g. 2001; DeBry & Sagel, 2001; Murphy et al., 2001) – an Hartenberger, 1996). Suprafamilial phylogenetic rela- assessment of long-standing substantiated by both tionships among Rodentia have been subject of palaeontological and neontological (anatomical) evi- particular controversy because of differing results dence (e.g. Tullberg, 1899; Luckett & Hartenberger, provided by phylogenetic analyses based on either 1993). molecular or morphological data. Some molecular In fact, because these studies differ in many aspects phylogenies have even failed to find strong support for of data and methodology, it is difficult to isolate spe- the monophyly of the order on the basis of amino-acid cific causes of the discrepancy as well as the resultant poorly resolved internal relationships. One of the most *Corresponding author. E-mail: [email protected] important areas is taxonomic sampling (Lecointre montp2.fr et al., 1993), with molecular phylogenies necessarily © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142, 105–134 105 106 L. MARIVAUX ET AL. limited to living or subfossil species. In contrast, mor- Hystricognathi, Anomaluroidea, Castoroidea, Gliroi- phological analyses may combine extant and extinct dea, Geomyoidea, Muroidea). It may, therefore, be pos- forms. Fossils frequently reveal unusual combinations sible that branching patterns deduced from ancient of characters not found in modern forms (Smith & Lit- extinct forms could shed light on the suprafamilial tlewood, 1994), and provide the only spatiotemporal relationships of extant lineages. Palaeontological data glimpse into the evolutionary history of a group. are frequently open to criticism because they mostly The evolutionary history of rodents is characterized depend on the quality of the fossil record. Features by the acquisition of complex and specialized morpho- related to the masticatory apparatus and more espe- logical traits of the masticatory apparatus (incisors, cially teeth have contributed prominently to taxo- cheek teeth, zygomasseteric structure including inser- nomic and phylogenetic analyses of extinct rodents tion of the masseter muscles and shape of the infraor- because they are the most frequently preserved skel- bital foramen). Several studies, including the analyses etal parts. of dental wear facets by Butler (1980, 1985), have Does any significant phylogenetic signal reside in shown that most masticatory patterns developed in dental characters? In terms of evolution, these partic- rodents can be identified from their initial Palaeogene ular anatomical structures have been generally radiation. regarded as labile because of the great amount of The most common higher-level taxonomies of parallel evolutionary changes observed (Butler, 1985; Rodentia have been based on different patterns Vianey-Liaud, 1985; Meng, 1990; Novacek, 1992; related to the following: (1) the ‘zygomasseteric Hunter & Jernvall, 1995), predominantly linked to complex’ (three subdivisions: Sciuromorpha, Hystri- food intake (Hillson, 1986). Nevertheless, recent comorpha and Myomorpha; Brandt, 1855, plus investigations into levels of homoplasy in the evolu- Protrogomorpha; Wood, 1965); (2) the angle of the tion of the mammalian skeleton have shown that the lower jaw relative to the plane of the incisors (two sub- level in dental traits produced no statistically signifi- divisions: Hystricognathi and Sciurognathi; Tullberg, cant differences from those recorded for cranial or 1899); (3) dental patterns (two subdivisions: Pentalo- postcranial traits (Sanchez-Villagra & Williams, phodonta and Non-Pentalophodonta; Stehlin & 1998). Schaub, 1951; Schaub, 1953a); (4) molecular phyloge- In this paper, as a contribution to these debates on nies (e.g. Huchon et al., 2000). high-level phylogeny and taxonomy of Rodentia, we Whereas the classifications of Brandt (1855), Wood present a cladistic assessment of the dental evidence (1965) or Schaub (1953a) have, by and large, been for early Tertiary rodent cladogenesis during the ini- abandoned due to suspected para- or polyphyly tial radiation – a morpho-palaeontological analysis (Hartenberger, 1985; Nedbal, Honeycutt & Schlitter, that has not hitherto been attempted. Our results are 1996), the classic basic subdivision introduced by Tull- compared with those inferred from molecular data berg (1899) remains in use. Hystricognathi appears to dealing with high-level rodent phylogeny. We use a be a valid taxon, well-defined in terms of its morpho- congruence-testing approach to assess which phyloge- logical and anatomical (Luckett & Hartenberger, netic hypotheses agree with each other and which fit 1993; Bryant & McKenna, 1995; Landry, 1999; the known fossil record best. Marivaux et al., 2002) and molecular (George, 1985; Nedbal et al., 1996; Huchon et al., 2000, 2002; Murphy et al., 2001; Huchon & Douzery, 2001) characters, and MATERIAL AND METHODS also supported by endoparasite studies (Hugot, 1999). SELECTED CHARACTERS In contrast, the taxonomic status of Sciurognathi as a natural group, as well as the internal relationships The fossil record of early Tertiary rodents predomi- within it, remains unclear, since the Hystricognathi nantly comprises isolated teeth or incomplete jaws; appear to be nested cladistically within