Mammal extinctions in the Vallesian (Upper Miocene)

Abstract

The term Vallesian was created by Crusafont (1950) to designate the first European Mammalian palaeofaunas containing the equid Hipparion, the remainder of the faunas being composed of typical elements coming from the Middle Miocene such as Micromeryx, Euprox, Sansanosmilus, Pseudaelurus, and Listriodon. Thus, the Aragonian-Vallesian boundary does not show a strong change among European Miocene mammalian faunas (Agusti et al., 1984). On the other hand, the Lower Vallesian/Upper Vallesian transition corresponds to a major biotic crisis. This boudnary is characterized by the disappearence of most of the Aragonian artiodactyl forms such as Protragocerus, Miotragocerus, Listriodon, Hyotherium, Parachleusastochoerus, etc. Among the rodents, this crisis affects the family Eomyidae and most of the cricetid and glirid species. On the other hand, a number of eastern elements appear in the area at the same time. This is the case of the suid Schizochoerus and the murid Progonomys. Other eastern forms are Tragoportax, Graecoryx, Adcrocuta, Paramachairodus, Microstonyx, etc. Most of these are typical elements of the next Mammal stage, the Turolian. Thus, whereas the Lower Vallesian fauna has a typical Aragonian composition except for Hipparion. After the Middle Vallesian event, the Upper Vallesian faunas are already largely Turolian in character. The possible factors involved in this extinction event are discussed.