Résumé
Deux faunes de mammifères, ont été reconnues dans le remplissage polyphasé de Lo Fournas 16 découvert lors de l’exploitation de la carrière de Baixas. La première, dénommée Lo Fournas 16-M, très riche en micromammifères et particulièrement en rongeurs, montre une association qui indique un âge Miocène supérieur (MN 11 ; Turolien ; Tortonien) estimé vers ± 9,5 Ma. La seconde dénommée Lo Fournas 16-P, beaucoup moins abondante est rapportée au Pliocène (MN 15) avec un âge estimé de 3 Ma environ. La faune d’âge miocène supérieur, connue pour sa richesse en rongeurs Murinae, livre trois espèces nouvelles : Hispanomys baixasi n. sp., Rotundomys n. sp., Eliomys lafarguei n. sp. Le remplissage polyphasé de la poche de Lo Fournas permet d’aborder à nouveau la question de l’homogénéité chronologique des assemblages fossilifères recueillis dans les zones karstiques.
Abstract
Two chronologically distinct faunas of mammals were recognized in the filling of a karstic cavity accessible for a while in the Baixas quarry (Pyrénées-Orientales, France). Small mammals, particularly rodents are abundant in the Lo Fournas 16-M which can be referred to zone MN 11 or Turolian (age ca. ± 9,5 Ma). The Lo Fournas 16-M fauna includes three new species: Hispanomys baixasi n. sp., Rotundomys sabatieri n. sp ., Eliomys lafarguei nov. sp. Hispanomys baixasi n. sp. is larger and morphologically more evolved than H. mediterraneus, and is distinct from H. freudenthali known in the Iberian Peninsula, being smaller, less hypsodont and having a labial anterolophid. Rotundomys sabatieri n. sp. is smaller than R. montisrotundi but morphological differences are weak. Eliomys lafarguei n. sp. is smaller than E. truci and the lower molar pattern is more complex. Several characters separate also E. lafarguei n. sp. from both E. assimilis and E. reductus. The rather poor Lo Fournas 16-P fauna (little material and few species) is Pliocene, the occurrence of the Murinae Stephanomys cf. donnezani indicating zone MN 15 (Middle Pliocene) and an estimated age ca. ± 3 My). This locality is an exemplary one to address recurrent questions about the biochronological use of faunas extracted from cavity fillings. Some palaeontologists argue that most of such faunas are mixtures of species that were not contemporaneous, and consequently that such faunas cannot be used for biochronology. The Lo Fournas 16 locality clearly demonstrates that despite several phases of infilling it is nevertheless possible (a) to separate two chronologically distinct faunas, (b) to isolate from a single assemblage the Pliocene species from the Upper Miocene ones, and (c) to record that distinct facies may give a homogeneous fauna while a single facies can deliver a chronologically mixed assemblage of species.
Dernière mise à jour le 11.06.2015