New Cricetodontini from the middle Miocene of Europe: An example of mosaic evolution

Abstract

A new species of Cricetodontini (Cricetidae, Rodentia, Mammalia), Cricetodon nievei sp. nov. from the Toril section (Toril 3A, Toril 3B, Toril 2) and Las Planas 5H is described. All this sites belong to the local biozone G3 (late Aragonian, late middle Miocene) from the Calatayud-Daroca Basin (Zaragoza, Spain). The new species displays a mosaic pattern consisting in a combination of primitive and derived characters: the upper molars have a basal Cricetodon-like pattern –short and not complete ectolophs –, whereas the lower molars share several derived features with the older representatives of Hispanomys – absence of metalophulid II. The generic assignation of the new taxon is further discussed and it is compared with all the species of Cricetodon and Hispanomys described until date. This mosaic evolutionary pattern of dental characters is also recognized in other species of Cricetodontini from Europe during the late Aragonian, although involving different combination of morphological characters. At this time, the diversity of the tribe increases, including species with complex morphology and higher intraspecific variability than the older representatives. The new species proposed here is morphologically close to Cricetodontini recorded outside the Calatayud-Daroca Basin, especially C. albanensis and H. decedens from France. Finally, the palaeoecological context of the new species is discussed; the stratigraphical distribution of Cricetodon nievei sp. nov. coevals changes in the faunal assemblages which are possibly related to an increase of humidity detected in the Calatayud-Daroca Basin.