Autopsie d’une radiation adaptative: Phylogénie des Theridomorpha, rongeurs endémiques du Paléogène d’Europe - histoire, dynamique évolutive et intérêt biochronologique

Abstract

The adaptive radiation of the rodents Theridomorpha occurred during a limited time window (middle Eocene to\rlate Oligocene), on an area restricted to Western Europe. In this paper, the phylogeny of this group is established via a cladistic\rassessment of 315 morphological characters (310 dental). The group of interest encompasses 110 upon 132 species (24 genera)\rof Theridomyoidea, and two genera formerly included within the Reithroparamyinae, and which are included here within the\rTheridomorpha. The outgroups include basal glires, Cocomys, Tanquammys and 16 Ischyromyiformes. A robust phylogenetic frame\ris produced, which allows clarifying the systematics of the Theridomorpha. Within the Ischyromyiformes, the Remyoidea (nov.\rsupfam.) are set apart from the Theridomorpha. Protadelomys and Tardenomys represent the earliest offshoots of the Theridomyoidea,\rbefore the dichotomy between Pseudosciuridae and Theridomyidae. This topology supports the former subfamilies Pseudosciurinae\rand Sciuroidinae within the Pseudosciuridae; and for the Theridomyidae: the Issiodoromyinae, Oltinomyinae, Columbomyinae,\rTheridomyinae, with at least one new subfamily (Patriotheridomyinae). The chronospecies (sensu Simpson), formerly considered\ras evolutionary lineages, appear in most cases as successive clades emerging in the stratigraphic order. The analysis of characters\rsupporting the main nodes allows consolidating the diagnostic characters of the taxa and their evolutionary trends, as well as\rdiscussing the various cases of parallelism and convergence in the evolution of structures and dental patterns (e.g., uniserial incisor\renamel for Issiodoromyinae and Patriotheridomyinae, or pseudo-multiserial for the most hypsodont Blainvillimys, Protechimys\rand Archaeomys; taeniodont dental patterns; lengthening of deciduous premolars for Patriotheridomyinae, Issiodoromyinae and\rTheridomyidae; selenodonty or lophodonty). Evolutionary dynamics are analysed with respect to environmental changes. Finally,\rbiochronological implications of the evolution of Theridomyoidea are discussed.