Abstract
The Aplodontoidea, now restricted to only oneNorth American species (Aplodontia rufa), have shown awide Holarctic extension since the Upper Eocene. As theirfossil record is poor, their phylogenetic relationships andthe origins of their successive radiations remain unclear.We perform here phylogenetic analyses, primarily based ondental evidence (94 dental of 97 characters), restricted toPaleogene and early Miocene taxa (46 taxa) in order toavoid biases introduced by substantially derived (divergent)taxa. We confirm the inclusion of some problematicgenera such as Cedromus or Douglassciurus withinSciuroidea rather than in Aplodontoidea. Ephemeromysand Lophallomys appear as the most basal members of theAplodontoidea, and Epeiromys is the closest outgroup ofthe Sciuroidea-Aplodontoidea clade. The relationshipsamong the ‘‘prosciurines’’ remain unclear, with paraphyleticgenera such as Prosciurus and Haplomys. Theirdiagnoses are reevaluated and a new genus is described.The Aplodontidae, including the clade of the latter, andHaplomys liolophus display a dichotomy betweenAnsomyinae and Aplodontinae, the two crown groups. Thefirst clade formed by the European species argoviensis anddescendens (referred to a new genus) can be proposed as asister group of the species of Ansomys. The second branchof the dichotomy includes the European Plesispermophilusand Sciurodon as basal groups. The species of Parallomysdo not form a clade, and the genus appears paraphyletic.The last dichotomy separates the Allomys clade from the‘meniscomyine’ clade. Comparisons of the selected speciesallow consideration of their patterns of dental evolution(e.g. enlargement of P4, development of a metaloph—protoloph disto-mesial connection, of crescentic shape inmain cusps and ectoloph, of a buccal protruding compressedmesostyle, of a metastylid crest or an anterior spurof the hypoconid, etc.). The split between sciuroids andaplodontoids occurred in North America, and then aplodontoidsdispersed rapidly throughout the whole Holarcticregion. The first aplodontid adaptive radiation took placeeither in North America or in Asia. Periodic exchangesoccurred between Europe, Asia and North America, andthe last radiations (meniscomyines) were restricted inNorth America.