It is in that period that our island appeared, or at least it was then that a block formed by Sardinia and Corsica together was cut from the European Continent and from the coasts of Provence. With an anticlockwise rotation this block became closer to the Tyrrhenean coasts on the Italian peninsula and formed a sort of archipelago consisting of separate islands and shallow sea.

At the beginning of the era, Sardinia was interested in cases of subsidence, that caused long tectonic depressions on the North-South line. The island was partly invaded by the sea, so that small islands, near to each other but separate, appeared: the Nurra, the Gallura, the Sulcis, the Iglesiente, and the Oriental Backbone formed this archipelago.

The Cenozoic Era can be considered revolutionary because of the the revival of flora and fauna. In particular, during this period the huge reptiles disappeared, leaving the place to warm blooded animals, the mammals, that conquested the earth through the millennia.

For these reasons, the discovery of the palaeontological layer in River Santo becomes very important.

This discovery happened almost by chance following excavations carried out during the building of a rubbish incinerator in the proximity of the thermo-electric power plant of River Santo, a few kilometers from Porto Torres.

Two amateurs, Dr. Mario Doria and Marzio Lamberti, collected small fragments of bones. These fragments where given to Professors Ginesu and Sias of the Faculty of Natural Sciences in Sassari who had already been studying geological sediments for some time in the same area. The findings were analyzed in collaboration with the University of Liege, and in particular, with palaeontologist Professor J.M. Cordy. They were able to reveal the identity and the age of the findings very quickly: about eight and a half million years old, which corresponds to the Miocene Superior, a period towards the end of the Cenozoic Era.

Amongst the findings, they recognized the remainings of an antelope of African origin, the Maremmia Lorenzi, the only one to date found in Sardinia, as well as crocodiles and other animals already known on the island.

In spite of only finding small fragments of bone, isolated teeth, or, in the case of the antelope, teeth and jaws (one with three molars and another with the 2nd and 3rd molars), the discovery is very remarkable, especially in the fact that it provides information relative to climatic conditions. A typical type of African faun was found, which shows how the climate was hotter than the present climate and certainly more humid.

This situation has been confirmed by the geological studies carried out on the sediments (the presence of the remainings of vegetables, layers of carbon, iron, and manganesium). Amongst the remainings of vegetables, there was a type of mangrove plant that is still present today in the lagoonal and marshy equatorial and sub-equatorial districts. The presence of crocodiles confirms the fluvial-deltic environment.

One could therefore imagine that River Santo was a water-way where crocodiles were once swimming, and a hilly area with forests and grassy open spaces where antelopes and bovines once could be found.

This was the environment in which "Proto" lived. The discovery of such remainings was already remarkable, but it widens with the finding of a highly developed primate, the Oreopitecus bambolii, a small antropomorphus monkey baptized "Proto".

The findings recovered consist of a fragment of jaw with the 3rd and 4th pre-molars still in place and some teeth that had been shed were found 5 meters deeper, still in perfect condition thanks to the hardening of the sediments.

Until now the Oreopitecus bambolii is still little known all around the world. The only certain site, apart from the recent Sardinian discovery, is Mount Bamboli near Grosseto, Tuscany. There, in 1858 a complete skeleton of an Oreopitecus was recovered. However, the remainings were crushed and scattered all around inside coal fragments.

According to rather unreliable sources, there were other findings of similar monkeys: in Moldavia, Russia, and in two African sites, Fort Ternan and Makobo island.

The palaeontological layer of Mount Bamboli, that was first described by Gervais in 1872, was classified by Professor Hurzeler (1965) as belonging to the branch of anthropomorphous monkeys because of some particular morphological characteristics. First of all the teeth structure, which, as shown is River Santo, is made by bicuspid and non-sectional and homorphic inferior premolars, which are typical of the evolved fossil primates.

The Tuscan site has shown the absence of diastema between premolars, canine and incisors, which are present in ordinary monkeys; furthermore, the five lumbar vertebrae were sturdy and the pelvis relatively wide and short.

All this evidence leads the scientists to classify the Oreopitecus bambolii as an anthropomorphous monkey, which is a primate close to the evolutionary line of the Hominid.

The shape of the pelvis and thigh bone suggests that the Oreopitecus had a two-footed gait and could walk in an erect position with the hind limbs. The front limbs are relatively long, which suggests a more arboreal life. Our Oreopitecus, like the one of Mount Bamboli, must have been around 1 to 1.10 meters tall, and had a weight of around 40 kilograms.

This growing interest about this type of monkey is due to the fact that it can be considered to be in between the oligo-miocenic and the quaternary Hominids. Apart from that, it is worth noticing that it belongs to an independent evolutionary line, but parallel to that of the anthropomorphous Primates line, which detached from the main line of the Hominids in the Paleogene and which probably became extinct during the Pliocene. This separation lead to the appearance of particular morphological characters, still orientated in the human direction. Some aspects of the teeth are singular and original, and show how the Oreopitecus differed from the other primates of the Miocene, as well as from the other African Hominids, the more evoluted Australopithecus.

One of our monkey's ancestors, the Nyanzapithecus, has been recognized in Lake Victoria, Kenya. The 14 million year old four-legged monkey could straighten itself to stand on its feet and had a particular dentition.

But how did this primate come to Sardinia from Africa? The Nyanzapithecus ascent towards the north, on the Tunisian coasts, and it would have probably crossed some natural bridges arriving in Sardinia and Tuscany.

The more likely hypothesis is that Sardinia acted as the bridge between Africa and that land that would become Tuscany (Thaler 1973). The latter region wasn't where it is now, but probably it was part of that archipelago mentioned before. Later on, the island became part of the peninsula on the East.

In this case, the primate of River Santo could be much older than that from Tuscany. Because of their insularity they have both developed singular characteristics which cannot be found in the rest of the European primates of that period.

According to another hypothesis (Azzaroli et al. 1987), Tunisia, Sicily, and Tuscany were joined together, and Sardinia could be reached from the northern part of Corsica.

The same way must have been followed by the other animals found on the site. Certainly, the antelope is of African origin.

A lot of headway has been made since the Aegyptopithecus appeared. This primate existed more than 34 million years ago and already possessed particular dentition characteristics, furthermore, the auditory duct and the facial morphology differed from those of ordinary monkeys. However, the first creature to be classified as a Homo appeared some 6 million years later. It was the Homo Abilis, a real two-footed Hominid, omnivorous and with a bigger enchefalus, which allowed it to make lithic instruments, therefore adapting itself to the surrounding environment.