Seventy eight species of mammals and 18 species of reptiles, birds and snails have been discovered on Samos. The majority of the fossils were found clustered in nine small regions (a few meters each) which have been termed bone beds or bone horizons. Within a bone bed, the animal bones were all mixed together and piled on top of each other. We know this from other bone beds found elsewhere on Earth (Bernor et al. 1996). Thousands of bones were also found at Pikermi (Miocene near Athens). In the Natural History Museum of London there are two blocks where jumbled bones were left intact. No pictures were ever taken of the fossils in situ during the numerous excavations on Samos. There are however a few unprepared blocks of bone masses. For example, block Y at the American Museum of Natural History, and two smaller blocks in Lausanne show a mass of jumbled bones. The pattern is similar to other bone beds from other regions of the world. Often a hippotherium (fossil horse) jaw will be open and a long bone of a giraffe limb will be passing through the jaw. Piles of long bones and ribs are all stuck together in dried mud (marl sediment). Bones of different sizes are found together. A massive deinotherium (elephant) skull (50 cm wide) will contain sediment in which a tiny bat skull (0.5 cm wide) is preserved. Tiny heel bones (astragali) are deposited next to an elephant tibia. Limbs and skulls are all packed together often so tight that museum technical preparators often had to destroy a bone to retrieve adjacent bones.
There are several scientific values of the fossils found on Samos. (1) They represent ancestors of many of the modern species and consequently they have been used to understand the evolution of modern taxa. (2) The fauna is located between three continents and has species which can be related mostly to those of central Africa (rainforest and savanna) and secondarily to those of Asia. The fauna is least similar to species from central Europe. Thus the zoogeographic value is that it enables us to better understand the Late Miocene distribution of taxa between these three continents. (3) The fauna was discovered early in the 19th century and hence many species have systematic types established from Samos specimens. The type of a species is the first, the template, which is used to name a newly discovered species. Other specimens of the same species found in other localities later, were based on types from Samos. (4) The fossils from Samos are well preserved. Most species are represented by complete skulls which is also untypical of fossil localities where fossils are fragmentary. In addition several species are known from many skulls. (5) The fauna is very rich for any standards (78 species of mammals). Modern African savanna faunas have less species of mammals than Samos although in East Africa the savannas are several hundred km2 wide. On Samos the richer faunas are sampled in an area no more than 1 km2.
How did bone beds form? One explanation is extensive and catastrophic death of taxa during droughts. This happens in Africa today where 30 or so animals cluster around a water hole. They stay there until they die. It is frequent that rains follow droughts and bones can be transported by water in small rivers. In torrential rains sheets of water can traverse the land outside river banks sweeping bones. These are termed flash or sheet floods. Subsequently, some of the bones can be washed into a low spot by floods. Bones would accumulate due to periodic droughts. Another explanation is that bones accumulating in a region where numerous animals live or pass by. Depressions in areas where animals live would enhance burial. Many of the Samos fossils are well preserved and often are skulls which are fragile. This implies rapid burial after death. Such burial would prohibit hyenas and other scavengers from destroying the bones. Burial in silt and limy marl is what is observed on Samos. Small depressions were present on the ground and probably bone beds are formed in such depressions. Evidence of the depressions can be found in quarries Q1, Q2 and Q4 where two massive layers of bone are superimposed on each other. Superposition of bone implies that a depression was persistent and a second layer of bone was deposited above the first before the depression filled up. These layers represent two primary bone accumulation events which could be separated even by thousands of years. Bones remaining on the surface have a short life span. They are either chewed up by carnivores or they form sun crack and break up.
The vegetation was rich with both forests and plains and the climate was subtropical and the forests were probably mild climate subtropical evergreen sclerophyllous (hard waxy coated leaves) (Axlerod 1975; Solounias et al. 1999). Orgetta (1979) described a scelorphyllous flora from Pikermi near Athens, which is a rich locality with many similarities to the fauna of Samos. Solounias et al. (1999) proposed a proto-savanna for Samos and Pikermi which was a precursor to modern savannas. There is a flora from Samos found below Mavradzei. The collection was made on a fresh road cut where exquisite details of layers were found. Now the surface of the road cut has oxidized preventing to see the published sedimentary details. Ioakim and Solounias (1985) sampled: Pinus, Tsuga, Taxodium, Sequoia, Quercus, Ulmus and Zelkova (which is the most abundant) near Mavradzei. They also found in less abundance: Alnus, Eucommia, Jungans and Carya – Platanaceae, Salicaceae, Cyrillaceae, Aquifoliaceae, and Nyssacaeae. Bushes of Amaratheceae-Chenopodiaceae, Graminae and Compositae were also identified. Ferns and Palmae were also present. This flora is similar to that of Pikermi and hence it was assumed that the flora changed little in the Samos region from 11 to 7 Ma (Ioakim and Solounias 1985).
The diversity of animal fossil life is unique (Solounias 1981a and 1981b; 1991; 1994). The most common fossils are mammalian ungulates (hoofed mammals). Many species are known from only 3-8 specimens. The majority of species, primarily ungulates, are known from 20 or more specimens each. For example hyena, hippotheria, rhinoceroses, the giraffid Samotherium and species of antelopes were common.
The ostriches were larger than the recent species in East Africa. There were small land tortoises and a very large one, Colossochelys, which was the size of a small car. There were small rodents and a bat similar to an Asian species. The bears were similar to modern species but were typical of Miocene bear species. There were dassies or hyraxes that were very large compared to their modern counterparts. The ant eating aardvark Orycteropus was smaller that the modern African species. The African like porcupine Hystrix was very similar to the one found on Samos. The species of pigs were a few and were basically very similar to the European wild boar (Sus). The mustelids (minks) were common and similar to modern species. The diversity of hyenas is characteristic of other Miocene localities from Asia. The hyenas are many and in various sizes. The majority are similar to modern dogs and foxes. The large hyena was a bone crusher (Adcrocuta) and was probably ancestral to the stripped and brown hyenas of Africa. The smaller species were similar to foxes and jackals (gracile) and are grouped into Hyaenotherium and Ictitherium. One species (Lycyaena) had long slender limbs like modern Chrysocyon (the maned wolf) and features resembling felids. Hyenotherium was basically like a modern coyote. The smallest hyenas were similar to civets. It is possible the modern aardwolf of Africa evolved from Ictitherium and modern brown and striped hyena from Adcrocuta. A very small hyena was similar to modern civet cats (viverids) and was named Plioviverrops. The felids (cats) were similar to modern taxa. There was a wild cat similar to modern wild cats (Felis). In addition there was a saber-toothed cat (Machairodus) which was abundant in the Miocene. Small saber-toothed felids (Metailurus) were also found on Samos. There were three species of elephants (proboscids): a large mastodon, a small mastodon and a deinothere. The mastodons had molar teeth shaped like breasts (hence their name mastobreastdont tooth) and four tusks two above and two on the jaw. Deinotherium had a small head and two down turned tusks on the lower jaw. They were distant relatives of the elephants.
The perissodactyls (odd toed ungulates) were many. Three toed horses dominated the mammalian fauna. Many species commonly known as hipparions or hippotheria are found on Samos. Hippotherium had three hooves per foot or hand whereas the modern horse has one. The central hoof bore the primary weight as in the modern horse. The side hooves were reduced but still functional. One difference in Hippotherium is a depression in front of the eye on the face. These were similar to depressions to those found in modern pigs, deer and antelope duikers and oribi today. The prevailing theory is that the depressions of Hippotherium had muscles supporting very large upper lips. There is also a possibility that these depressions had face glands as do duikers and oribi. If they had lip muscles, they may also have had a small proboscis as tapirs. Various hippotheria differ is size and the number and shape of skull depressions in front of their eye. One of the hippotheria was small. Most species were the size of a donkey. Ancylotherium was a bizarre species. It had an inclined back like a hyena but it was a herbivore and a close relative to the horses and the rhinoceroses. It also had, instead of hooves, huge clawed hands. Its snout was very delicate and slender and it had broad teeth for browsing.
The rhinoceroses were of two types. There were species without horns. These species had a very broad lower lip and were called chilotheria (lip mammals). They also had lower tusks reminiscent of those of pigs and hippopotamuses. The rest of the rhinos are similar to the modern African black and white rhino but they have many differences and hence are ancestral to them. They had two horns marks of which can be discerned on the profile of the nasal bone. There was also a Dicerohrinus which is still extant as the Sumatran rhino. Dicerohrinus was a common genus during the Middle and Late Miocene.
The deer were similar to the European roe deer (Pliocervus) but there were also species of more primitive deer such as a muntjack and even a tragulids (Muntiacus and Dorcatherium). There were many giraffes. Palaeotragus and Samotherium were both large species (the former the size of a large deer or an elk and the later even larger than a moose). Their horns were straight and had an unusual feature. Often the skin of the horn peeled off and bare bony tips were exposed. This is an unusual feature for any animal to have bone exposed to the air. Palaeotragus and Samotherium had medium in length necks like a modern gerenuk. Their limbs were short in comparison to the limbs of modern giraffe. There were two sivathere species of giraffes which were even larger than Samotherium and they had short necks and stalky limbs. None of these giraffids were ancestral to modern giraffe. In addition there was a species (Bohlinia) which resembled the modern giraffe in that it had long limbs and a long neck. This species may not actually be related to modern giraffe and in that case the long neck would be due to parallel evolution. If that was the case, then there would be no ancestor of the modern giraffe found on Samos. Schansitherium is a species similar to Palaeotragus. Birgerbohlinia was like a sivathere but it was different in the limbs.
Many antelope bovids were found on Samos (Gentry 1971). The majority of the antelopes were similar to modern tragelaphines (kudus) and deer in dentition. They presumably browsed most of the time. There were several relatives of the modern Indian nilgai and chusigha. The most common ones were Miotragocerus and Tragoportax. There were antelopes similar to the Indian black buck and to other spirally horned species. The most common ones were Protragelaphus and Prostrepciceros. The gazelles were small and most similar to those found in Sudan (Gazella dorcas). There were early ancestors (Samokeros) of the bovine group (bison, cows and buffaloes). There were distant ancestors (Palaeoryx) to the modern sable and oryx antelopes. There were undisputable ancestors (Pachytagus) to the modern goats. The goat ancestors had many similarities with modern goats such as short premolars and simple teeth. But they also had differences like primitive horns which did not have sinuses in them and long metapodials unlike the short modern goat metapodials. Perhaps these are adaptations for climbing mountains and Pachytragus would be more of a species inhabiting. Criotherium and Parurmiatherium were distant relatives of modern musk oxen and takins. Palaoeoreas was a spiral antelope of unclear affinities.