Distribució dels rosegadors fòssils de la Mediterrània occidental durant el Neogen

Resum

In this paper a summary is done of the succession of Rodent microfaunas in the Mediterranean during the Neogene. The base of the Neogene (Agenian) is characterized both in the Iberian Peninsula and South of France by the abundance of Cricetidae, Eomydae and Gliridae. After, the Cricetidae of Oligocene origin disappear (Eucricetodon, Pseudocricetodon) and new genera from this family came from Asia (Democricetodon, Eumyarion, Megacricetodon, Cricetodon). They were accompanied by several forms: Proboscidea (Gomphotherium, Deinotherium), Artiodactyla (Tragulidae, Suidae, Cervidae), Primates (Pliopithecus) and Perissodactyla (Chalicotherium). In this phase (Orleanian, Lower Miocene), cases of insularity are found at Sardinia, together with African elements (Ctenodactilidae). Presence of African elements (Ctenodactilidae, Phiomyidae), followed by insularity, took place in the Upper Oligocene of Majorca (Balearics).
The Middle Miocene (Astaracian) is characterized in Western Europe by the appearence of many inmigrators as well as the extinction of the genera from the Lower Miocene. These Middle Miocene faunas appear to be humid and forested. The later is in contrast with that which is observed in the interior of the Iberian Peninsula, where a dry and low diversified microfaune had progressed. The forested microfauna is also present at Crete. On the other hand, North African microfaunas show a clear endemism in relation to Europe but, in Turkey European elements coexisted together with some african ones.
At the begining of the Upper Miocene (Vallesian), many inmigratory waves came to Europe. They form the so called Hipparion-faunas. Together with Hipparion, there appear Machairodus, Progonomys, Tragocerus, Microstonyx, Alilepus, etc. All these genera did not arrive at the same moment, so that a coexistence between the Astaracian elements and the new inmagrators is a characteristic of the Vallesian. The forested conditions persisted in the Lower Vallesian in the whole Europe, as well as the endemism of the North African margin. Nevertheless, a tendency to the hypsodonty is observed in most Cricetidae from the two sides, and many extinctions took place.
After the Vallesian (Turolian), an open, «savanne»-like biotope was present in the whole Mediterranean margins, with a high diversity of Muridae (Parapodemus, Occitanomys, Valerimys) and few Cricetidae. Endemism between the two extremes of the Mediterranean begins. The forested biotope inherited from the Middle Miocene persisted in Center Europe. In this phase, isolation and correlative cases of insularity are present in Italy (Gargano, Baccinello).
At the end of the Miocene, in the so-called «Messinian crisis., the regression in the Mediterranean allows the pass of species across the Gibraltar Straits. This is the case of some African rodents which appear in Spain (Gerbillus, Paraethomys) and also of Hippopotamus. On the other hand, some European genera pass to Africa.
In the East, the base of the Pliocene in characterized by the mixture of European, Asiatic and African elements. With the Pliocene transgression, the circummediterraean endemic fauna of Muridae comes to an end and new palearctic Rodents come to the South West of Europe (Arvicolidae), performing the base of the future Quaternary faunas.
Finally, some considerations on the origin of the insular endemisms from the Quaternary are made.