SECOND FLOOR - ENGLISH
Fossils: A look back to the past. Life in the Balearic Islands throughout all ages of the earth.
The visit of Joan Salvador i Riera to Mallorca and Menorca in 1711 marked the beginning of research on the flora of the Balearic Islands. Together with his brother, Josep Salvador, who also collected plants in Minorca in 1725, belonged to a dynasty of pharmacists who played an extremely important role in pre-Linnaean botanical studies in Catalonia. The subsequent introduction of Linnaeus’ systematics in almost all of Europe would later characterise most of the botanical studies during the Age of Enlightenment.
The reign of Carlos III is significant for having adopted the cultural values of the Enlightenment. George Cleghorn and John Armstrong published their works in Menorca, which at that time was under British sovereignty. In Mallorca, the scientific unrest was at that time represented by Bonaventura Serra and Cristòfol Vilella.
The figure of the geographer interested in natural science emerged coinciding with the founding of the “Real Sociedad Económica de Amigos del País” (Royal Economic Society of Friends of the Country). The works of Jeroni de Berard, Manuel Abad y Lasierra (first bishop of Eivissa) and José Vargas Ponce contain naturalist information interspersed with geographic descriptions.
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The Salvador family, a long line of reputable pharmacists and botanists, some of whom collected plants in the Balearic Islands.
- Hypericum balearicum, a species collected by Joan Salvador i Riera during his botanical expeditions in 1711 in Mallorca and Menorca.
- Drawing from the work “The History of the Island of Minorca”, published by John Armstrong in 1752.
- Portrait and episcopal seal of Manuel Abad y Lasierra, author of the first geographic description of Eivissa and Formentera.
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Covers of the most important books by Linnaeus.
- Covers and various fragments of “Descripciones de las Islas Pithiusas y Baleares” including some naturalistic information, by the geographer José Vargas Ponce.
Fossils are any remains of organisms or traces of their activity that remain preserved in the rocks (normally in sedimentary rocks, but also in volcanic as well).
Not everything that looks like a fossil has a biological origin. Sometimes, Nature “creates” fake fossils.
- It looks like a fossil, but it is not.
- It is a fossil, but it does not look like it.
Many of the organisms that have existed have not left any trace. Fossilisation depends on several biological, physical and chemical processes and transformations, through which a certain organic remain transforms into one or several fossils.
- Shallow sea waters (continental platform) and continental wetlands are the most suitable places for fossilisation, especially for those organisms with shells or a hard skeleton.
- Once dead, the organic remains sink to the bottom, together with other sediments brought by rivers or streams.
- The remains are buried under the sediments. If the area is anoxic, the organism alteration process can be slowed down.
- Over time, the shells or other hard parts, and exceptionally the soft parts, undergo chemical transformation consisting of mineral precipitation and other complex processes.
Depending on the physical, chemical and biological conditions, different types of fossils can be formed:
- The whole organism is preserved as it was (such as the case of amber).
- Only the hard parts of the organism are preserved.
- The original minerals from the hard parts are replaced by other minerals through the process of recrystallization or replacement during the diagenesis.
- Silicification of wood is a case of cementation, turning it into xylopal.
- Coalification of plant remains.
- The dissolution of the organisms can produce internal and external moulds.
- Recristallisation, for example in the alteration of aragonite in an skeleton (formation of calcite).
- Pyritisation of the hard parts during the fossilization process, either by mineralisation or by cementation.
- Ichnofossils: only preserve traces of the activity of the organisms (tracks, footprints, traceways). In this case, in order for the fossil to be formed, it is not necessary that the producer organism dies.
- Microfossils: they are small fossils that can be found in sedimentary rocks, both from continental and marine origin. Micropalaeontology studies and interprets microfossils, and encompasses many kinds of microscopic fossils, from remains of microorganisms to isolated elements or skeletal fragments of larger organisms.
Charles Darwin was one of the first naturalists to realise the importance of the fossils as proof of biological evolution.
The fossils of Archaeopteryx, discovered in Bavaria in 1860, provided evolutionary scientists with one of the most solid proofs to demonstrate their theories on the existence of intermediate steps between species. Archaeopteryx was, at first, considered a reptile with bird traits, but it is now interpreted as a true bird (the most primitive one).
The Palaeozoic era lasted more than 300 million years. During this long period of Earth’s history, most primitive multicellular life forms typical of the latest Precambrian (the oldest known macrofossils have been dated between 560 and 580 million years) died out. In the earliest Cambrian, there was an explosion of biological diversity that gave rise to many new body plans. Many of these organisms still exist nowadays, but a large part disappeared at the end of this period.
During the subsequent periods of the Palaeozoic, known as Ordovician, Silurian, Devonian, Carboniferous and Permian, the world underwent great geological and climatical transformations, that determined the rise of new marine and continental life forms. The first fishes (ostracoderms) appeared in the late Cambrian – early Ordovician. Amphibians appeared in the late Devonian. During the Carboniferous, primitive giant vascular plants (producers of important coal deposits) and insects dominated the terrestrial ecosystems. Finally, in the late Permian, a great mass extinction affected most of biological groups, both marine and continental. his marks the end of the Palaeozoic era.
The Palaeozoic era in the Balearic Islands. In the Balearic Islands, palaeozoic rocks can only be found in the northern sector of the island of Menorca. On Mallorca, the only known outcrops are very small and have been attributed to the lower Carboniferous (although they contain no identifiable fossils). On Menorca, there are plant remains, molluscs and scarce trilobites, dated as late Devonian, and also bone remains of a large, unidentified reptile from the late Permian.
Balearocrinus breimeri is a crinoid (sea lily) that lived in the Balearic zone in the late Carboniferous. The few fossils known are from Menorca, and a similar species has been found in the mountains of Cantabria (Balearocrinus cantabricus).
The trilobites, an emblematic example of the animal life in the Palaeozoic. 500 million years ago, trilobites were the most common arthropods in the sea. They had already diversified into many species. The traces of their biological activity (burrowing, feeding or walking) also became fossils, among others, the ichnofossil Cruziana (an ichnogenus also related to the activity of other aquatic arthropods). Only few, poorly-preserved trilobite specimens are known from the Balearic Islands, which have been found in the strata of the late Devonian of Menorca. Trilobites became extinct at the end of the Permian, 245 million years ago.
During the subsequent periods of the Palaeozoic, known as Ordovician, Silurian, Devonian, Carboniferous and Permian, the world underwent great geological and climatical transformations, that determined the rise of new marine and continental life forms. The first fishes (ostracoderms) appeared in the late Cambrian – early Ordovician. Amphibians appeared in the late Devonian. During the Carboniferous, primitive giant vascular plants (producers of important coal deposits) and insects dominated the terrestrial ecosystems. Finally, in the late Permian, a great mass extinction affected most of biological groups, both marine and continental. his marks the end of the Palaeozoic era.
The Palaeozoic era in the Balearic Islands. In the Balearic Islands, palaeozoic rocks can only be found in the northern sector of the island of Menorca. On Mallorca, the only known outcrops are very small and have been attributed to the lower Carboniferous (although they contain no identifiable fossils). On Menorca, there are plant remains, molluscs and scarce trilobites, dated as late Devonian, and also bone remains of a large, unidentified reptile from the late Permian.
Balearocrinus breimeri is a crinoid (sea lily) that lived in the Balearic zone in the late Carboniferous. The few fossils known are from Menorca, and a similar species has been found in the mountains of Cantabria (Balearocrinus cantabricus).
The trilobites, an emblematic example of the animal life in the Palaeozoic. 500 million years ago, trilobites were the most common arthropods in the sea. They had already diversified into many species. The traces of their biological activity (burrowing, feeding or walking) also became fossils, among others, the ichnofossil Cruziana (an ichnogenus also related to the activity of other aquatic arthropods). Only few, poorly-preserved trilobite specimens are known from the Balearic Islands, which have been found in the strata of the late Devonian of Menorca. Trilobites became extinct at the end of the Permian, 245 million years ago.
During the Carboniferous, as opposed to nowadays, a great part of the world was dominated by forests of large, non-flowering plants. Giant lycophytes, horsetails (sphenophytes), primitive ferns (filicophytes) and seed ferns (pteridospermatophytes) -already dominant in the late Devonian. Sigillaria and Lepidodendron (licophytes), two of the most abundant genera, could achieve heights of 35 m or more. When these trees, generally inhabiting swamps and marshes, died, thick layers of peat were slowly formed. Over time, it would become mineral coal. It is in these coal deposits where fossils of these spectacular plants are found. Generally, they consist of remains of their trunks or bark imprints, but sometimes the delicate imprints of their fronds can be found as well.
The Triassic has been considered as a period of transition between the “old” life and the “modern” life. It begun 245 million years ago and it is the first period and the longest of the Mesozoic. Over the Triassic, the supercontinent Pangaea achieved its maximum extension. On the continent, the primitive reptiles that appeared in the late Permian evolved and begun to dominate an almost uniform world, which gave rise to dinosaurs, pterosaurs and mammals. In the ocean, the first marine reptiles were appearing, and at the end of this period, the first ichthyosaurs, already completely adapted to the ocean life and with a hydrodynamic design reminiscent to modern dolphins. Most marine invertebrates started developing ways to escape predators, which were increasingly abundant. The scleractinian corals appeared, slowly forming great reefs.
The Balearic Islands during the Triassic. In the Triassic, the area currently occupied by the Balearic Islands was located in a vast continental margin, characterised by broad wetlands beside the sea. As in the rest of the world, volcanism was present. The scarce marine Triassic fossils collected in the Balearic Islands, as the ammonoid Ceratites, show that there were also periods of flooding of the platforms. In the continental environments, there were large reptiles (Ticinosuchus) and in the coastal zones, amphibian marine reptiles (Nothosaurus). The fossil record of the Balearic Islands also shows the presence of ephemeropteran insects (mayflies), beetles, plant remains, fishes and small branchiopod crustaceans that lived in the swampy zones.
Tetrapod fossil tracks known as Cheirotherium are frequent in the lower Triassic of Europe. These were initially attributed to large, primitive amphibians, but more recently they have been linked to other animals, especially to the reptile Ticinosuchus, a carnivorous tetrapod. On Mallorca, these ichnites have been found at Banyalbufar (Buntsandstein).
Nothosaurs were long-necked reptiles with feet transformed into paddles, which were used to swim together with the movement of their tail. Nothosaurs were dominant during the Muschelkalk (middle Triassic) and died out during the latest Triassic. On Mallorca, only a few isolated Nothosaurus vertebrae have been found in the Muschelkalk gypsum deposits of the Serra de Tramuntana.
The Balearic Islands during the Triassic. In the Triassic, the area currently occupied by the Balearic Islands was located in a vast continental margin, characterised by broad wetlands beside the sea. As in the rest of the world, volcanism was present. The scarce marine Triassic fossils collected in the Balearic Islands, as the ammonoid Ceratites, show that there were also periods of flooding of the platforms. In the continental environments, there were large reptiles (Ticinosuchus) and in the coastal zones, amphibian marine reptiles (Nothosaurus). The fossil record of the Balearic Islands also shows the presence of ephemeropteran insects (mayflies), beetles, plant remains, fishes and small branchiopod crustaceans that lived in the swampy zones.
Tetrapod fossil tracks known as Cheirotherium are frequent in the lower Triassic of Europe. These were initially attributed to large, primitive amphibians, but more recently they have been linked to other animals, especially to the reptile Ticinosuchus, a carnivorous tetrapod. On Mallorca, these ichnites have been found at Banyalbufar (Buntsandstein).
Nothosaurs were long-necked reptiles with feet transformed into paddles, which were used to swim together with the movement of their tail. Nothosaurs were dominant during the Muschelkalk (middle Triassic) and died out during the latest Triassic. On Mallorca, only a few isolated Nothosaurus vertebrae have been found in the Muschelkalk gypsum deposits of the Serra de Tramuntana.
During the Jurassic, the supercontinent Pangaea started to fragment. In the long period of time formed by the Jurassic and the Cretaceous (about 143 million years), the Earth’s climate was warmer than today, with wider tropical and subtropical areas. Temperate areas stretched into the poles, which were devoid of ice. During this timespan, the shallow, coastal seas -the most favourable for life- occupied a great extension, with an important proliferation of calcareous-shelled animals. On land, gymnosperm plants, cicas and ginkgoes were dominant during the Jurassic, whereas angiosperms (flowering plants) appeared in the early Cretaceous. The Triassic dinosaurs underwent a spectacular diversification into three groups: herrerasaurids, saurischians and ornitischians. By the end of the Jurassic, the sauropods were the largest and heaviest land animals that ever existed. In the latest Cretaceous, 65 million years ago, the typically Mesozoic biological groups -including all dinosaurs- suffered a decline or were completely wiped out.
One of the most well-known and controversial European dinosaurs is Iguanodon from the lower Cretaceous, which was first discovered in England in 1820. Iguanodon, known in the Iberian Peninsula by the species Iguanodon bernissartensis, were about 10 m long and probably weighed more than 4 tons. It is currently believed that Iguanodon kept their tails straight backwards in order to provide a counterweight for their body, which allowed them to maintain an almost horizontal backbone. This, and the structure of their forefeet, suggests that Iguanodon could walk both on four feet and on the two hindfeet. Iguanodon were herbivorous and shredded their food using their specialised teeth.
Ichthyosaurs were marine reptiles that probably evolved from a terrestrial ancestor. They were superficially very similar to modern dolphins. They were viviparous, which is known thanks to complete and exceptionally well-preserved fossils. Ichthyosaurs were about 2 m long, but some Triassic species (such as Shonisaurus) reached 15 m. The fossilised vertebrae of Ichthyosaurus are common in the European Jurassic marine deposits.
The Jurassic and Cretaceous in the Balearic Islands. During the first half of the Jurassic, the dominant marine environments in the Balearic Islands were shallow carbonate platforms, derived from the shallow seas formed on the continental areas during the Triassic. Dirong the second half of this period, coinciding with one of the opening phases of the Atlantic ocean and the subsequent widening of the Tethys sea, the fossil record suggests that the waters were deeper, with abundance of continental slope and pelagic species. During the lower Cretaceous, the depth of the marine area corresponding to the Balearic Islands increased progressively. However, about 128 million years ago, the fossil record contains species indicating progressively shallower environments. Probably, by the end of the Cretaceous there were vast extensions of land again.
One of the most well-known and controversial European dinosaurs is Iguanodon from the lower Cretaceous, which was first discovered in England in 1820. Iguanodon, known in the Iberian Peninsula by the species Iguanodon bernissartensis, were about 10 m long and probably weighed more than 4 tons. It is currently believed that Iguanodon kept their tails straight backwards in order to provide a counterweight for their body, which allowed them to maintain an almost horizontal backbone. This, and the structure of their forefeet, suggests that Iguanodon could walk both on four feet and on the two hindfeet. Iguanodon were herbivorous and shredded their food using their specialised teeth.
Ichthyosaurs were marine reptiles that probably evolved from a terrestrial ancestor. They were superficially very similar to modern dolphins. They were viviparous, which is known thanks to complete and exceptionally well-preserved fossils. Ichthyosaurs were about 2 m long, but some Triassic species (such as Shonisaurus) reached 15 m. The fossilised vertebrae of Ichthyosaurus are common in the European Jurassic marine deposits.
The Jurassic and Cretaceous in the Balearic Islands. During the first half of the Jurassic, the dominant marine environments in the Balearic Islands were shallow carbonate platforms, derived from the shallow seas formed on the continental areas during the Triassic. Dirong the second half of this period, coinciding with one of the opening phases of the Atlantic ocean and the subsequent widening of the Tethys sea, the fossil record suggests that the waters were deeper, with abundance of continental slope and pelagic species. During the lower Cretaceous, the depth of the marine area corresponding to the Balearic Islands increased progressively. However, about 128 million years ago, the fossil record contains species indicating progressively shallower environments. Probably, by the end of the Cretaceous there were vast extensions of land again.
During the 143 million years corresponding to the Jurassic and the Cretaceous, the area currently occupied by the Balearic Islands was completely submerged. This is the reason why only remains of marine organisms are found on the Islands. Most animals that roamed the Jurassic sea floor are similar to those of today. During the Jurassic and the Cretaceous, the cephalopods with external shell achieved great evolutionary success, together with the belemnites -cephalopods with an internal shell, of which only the terminal bullet-shaped tip is usually preserved (the rest is made up of aragonite and usually dissolves). By the end of the Jurassic, some giant species of ammonites reached diameters of 2 m. Among many other invertebrates, some groups were specially abundant: crinoids, urchins and starfish; brachiopods; sponges; scleractinian corals; and clams and snails. The modern fish (teleosteans) begun to dominate the sea and the continental waters, together with the sharks. The marine reptiles also underwent diversification.
The Palaeogene in the Balearic Islands. There are no known geological nor palaeontological records of the earliest Tertiary (Palaeocene) or the early Eocene in the Balearic Islands. This is probably because part of the Balearic area was emerged since the end of the Cretaceous. During the middle and late Eocene, there were several marine transgressions (sea level rises) in that area, which left many sedimentary deposits with protists, especially nummulites, which were unicellular organisms that indicate shallow and well-illuminated waters. During this time, coastal lacustrine environments were also formed in emerged areas and, during the late Eocene and early Oligocene, they were completely continental and far from the coast, dominating the centre of the island. These lakes were probably fed by freshwater courses coming from the existing mountains between what are now the Iberian Peninsula and the Balearic Islands.
The Palaeogene in the Balearic Islands. There are no known geological nor palaeontological records of the earliest Tertiary (Palaeocene) or the early Eocene in the Balearic Islands. This is probably because part of the Balearic area was emerged since the end of the Cretaceous. During the middle and late Eocene, there were several marine transgressions (sea level rises) in that area, which left many sedimentary deposits with protists, especially nummulites, which were unicellular organisms that indicate shallow and well-illuminated waters. During this time, coastal lacustrine environments were also formed in emerged areas and, during the late Eocene and early Oligocene, they were completely continental and far from the coast, dominating the centre of the island. These lakes were probably fed by freshwater courses coming from the existing mountains between what are now the Iberian Peninsula and the Balearic Islands.
The Palaeogene is divided into three periods: the Palaeocene, the Eocene and the Oligocene, spanning more than 40 million years. At the beginning of the Tertiary, tropical and subtropical climates expanded over the planet, and even in the poles there were vast deciduous forests. The extinction of dinosaurs, at the end-Cretaceous, had important consequences on the terrestrial ecosystems world-wide, and permitted the diversification of mammals (which had appeared in the upper Triassic) in the Palaeocene forests. During the Eocene, the climates of the Earth became increasingly warm, and the north and south poles were even covered by deciduous forests with large leaves, in which mammals were the dominant taxa. In the Oligocene, climates had become more temperate and seasonal. Meanwhile, the Palaeogene sea also recorded these climate events with significant sea level changes. During the Eocene, the south of present-day Europe was formed by several island territories, with surrounding waters inhabited by animals similar to those living today, which left an important fossil record.
Cainotherium was a primitive artiodactyl mammal without any known modern relative. It has been related to camels, although it was hare-sized. Cainotherium appeared in Europe during the late Oligocene, diversified and, later, became extinct about 20 million years ago, in the early Miocene.
Nummulites is a genus of unicellular organisms (rhizopodian protozoans) of the order of rotaliin foraminifers, which was especially abundant and diverse in all the tropical-subtropical seas during the Eocene. Whereas most modern foraminifers are microscopic, some nummulites reached a diameter of 14 cm. Their coin- or lentil-shaped shells became fossils and formed rocks that, often, are constituted almost exclusively by the remains of these protozoans. A single nummulites species (Nummulites venosus) has survived until the present day in the tropical seas of the Indo-Pacific realm.
Cainotherium was a primitive artiodactyl mammal without any known modern relative. It has been related to camels, although it was hare-sized. Cainotherium appeared in Europe during the late Oligocene, diversified and, later, became extinct about 20 million years ago, in the early Miocene.
Nummulites is a genus of unicellular organisms (rhizopodian protozoans) of the order of rotaliin foraminifers, which was especially abundant and diverse in all the tropical-subtropical seas during the Eocene. Whereas most modern foraminifers are microscopic, some nummulites reached a diameter of 14 cm. Their coin- or lentil-shaped shells became fossils and formed rocks that, often, are constituted almost exclusively by the remains of these protozoans. A single nummulites species (Nummulites venosus) has survived until the present day in the tropical seas of the Indo-Pacific realm.
The lignite coal deposits of the central sector of Mallorca (Selva, Sineu, Alaró, Binissalem, Lloseta and Alcúdia) preserve an exceptional fossil assemblage that has made it possible to precisely reconstruct the palaeoenvironments of Mallorca during the Eocene-Oligocene transition. The fossils evidence the existence of a rich forest vegetation, which developed around the freshwater areas, formed by trees that nowadays live in much warmer latitudes, such as fig trees (Ficus), redwoods (Sequoia), camphor trees (Cinnamomum), Judas tree (Cercis), soapberries (Sapindus), magnolia trees (Magnolia), laurel trees (Laurus), and palm trees (Sabal and Phoenicites). There are also fossils of species that are nowadays typical of more temperate areas, such as maple trees (Acer). Nevertheless, most fossils indicate a similar environment to that of the subtropical forests of modern North and Central America. Those water environments were densely populated by reeds (Phragmites), and the bottom was roamed by an invertebrate fauna of which only snails remain preserved (Planorbis sp., among other freshwater species). Large freshwater turtles probably fed on those invertebrates. Coal deposits were mostly formed by the reeds, whereas the other plants and trees living outside the water also remained preserved as fossils in the lignites.
A rich and varied fauna populated those forest areas 40 million years ago on Mallorca. Coal deposits have preserved skeletal fragments and fossilised faeces. Noteworthy are the perissodactyl mammal fossils, similar to modern horses and tapirs, such as Lophiotherium (equid), Plagiolophus (palaeotheriid) and Diplobune and Anoplotherium (anoplotheriids). The extinct group of anthracotheriids (Anthracotherium), related to modern pigs and hippopotamuses, also inhabited those lands.
A rich and varied fauna populated those forest areas 40 million years ago on Mallorca. Coal deposits have preserved skeletal fragments and fossilised faeces. Noteworthy are the perissodactyl mammal fossils, similar to modern horses and tapirs, such as Lophiotherium (equid), Plagiolophus (palaeotheriid) and Diplobune and Anoplotherium (anoplotheriids). The extinct group of anthracotheriids (Anthracotherium), related to modern pigs and hippopotamuses, also inhabited those lands.
Halianassa cuvieri was a large sirenian that inhabited the Balearic Islands during the late Miocene (about 10.2 and 6.3 million years ago), when the Mediterranean was a tropical sea with coral reefs and an environment similar to the modern Caribbean Sea. Sirenians are mammals that are completely adapted to the aquatic life. Nowadays, some tropical species of this group remain, in the form of dugongs and manatees that live in the tropical Atlantic waters (manatees) and Indic and western Pacific waters (dugongs). Just like their modern counterparts, Halianassa exclusively fed on sea grasses. Their preferred habitat were shallow seagrass meadows in reef and lagoon environments.
In the early Miocene, about 23 million years ago, an important climate change led the world towards increasingly warmer and drier conditions. Although the Alpine Orogeny had already begun by the end-Cretaceous, it is during the Miocene when the last large mountain ranges of the Earth were formed. This had profound effects on the world climate, as it affected the atmosphere and hydrosphere global circulation. The closing of the Tethys sea would also mark the origin of the modern-day Mediterranean.
Regarding biodiversity, the Miocene was a key period in the assemblage of the modern biosphere, in which mammals already had a completely dominant role on land, added to the conquest of water and sky. This period also saw the onset of many groups, such as the well-known horses.
The Pliocene started about 5 million years ago, and ended about 1.7 million years ago with the beginning of the Quaternary period. The modern plant communities that nowadays exist all over the world started to configure during that time, under cyclical climates that exist today. However, because of the glaciations, this vegetation suffered important distribution changes during the Quaternary.
The Miocene in the Balearic Islands
From the early Miocene (about 23 million years ago) to the middle Miocene, the Balearic area underwent tectonic movements that affected an important part of the Mediterranean and fostered notable palaeogeographical changes, including the formation of the Balearic Islands themselves. About 13 million years ago, the palaeogeographical aspect of Mallorca was already similar to nowadays. This “proto-Mallorca” was formed by two parallel islands, corresponding to the modern Tramuntana and Llevant mountain ranges, with a seaway in between. By the end of the Miocene, the Balearic sea level started to drop spectacularly because of the general because of the general lowering of the sea level in the Mediterranean. The dinotheres (Deinotherium) were large, proboscidean mammals that lived in Eurasia during the early and middle Miocene. Dinotheres were relatives of mastodonts and elephants, and were characterised by tusks that were only well-developed in the lower jaw, curved downwards and backwards. Dinotheres became extinct in Europe during the late Miocene, but they survived in the African continent until the middle Pleistocene.
Regarding biodiversity, the Miocene was a key period in the assemblage of the modern biosphere, in which mammals already had a completely dominant role on land, added to the conquest of water and sky. This period also saw the onset of many groups, such as the well-known horses.
The Pliocene started about 5 million years ago, and ended about 1.7 million years ago with the beginning of the Quaternary period. The modern plant communities that nowadays exist all over the world started to configure during that time, under cyclical climates that exist today. However, because of the glaciations, this vegetation suffered important distribution changes during the Quaternary.
The Miocene in the Balearic Islands
From the early Miocene (about 23 million years ago) to the middle Miocene, the Balearic area underwent tectonic movements that affected an important part of the Mediterranean and fostered notable palaeogeographical changes, including the formation of the Balearic Islands themselves. About 13 million years ago, the palaeogeographical aspect of Mallorca was already similar to nowadays. This “proto-Mallorca” was formed by two parallel islands, corresponding to the modern Tramuntana and Llevant mountain ranges, with a seaway in between. By the end of the Miocene, the Balearic sea level started to drop spectacularly because of the general because of the general lowering of the sea level in the Mediterranean. The dinotheres (Deinotherium) were large, proboscidean mammals that lived in Eurasia during the early and middle Miocene. Dinotheres were relatives of mastodonts and elephants, and were characterised by tusks that were only well-developed in the lower jaw, curved downwards and backwards. Dinotheres became extinct in Europe during the late Miocene, but they survived in the African continent until the middle Pleistocene.
During the Burdigalian (early Miocene), marshes and coastal wetlands developed in the NW zone of Mallorca. They were originally brackish water marshes that, over time, became true freshwater lakes. The leaves of the trees inhabiting the nearby forests, fell into those lakes and remain preserved in an exceptional deposit in Collet de Bini (Fornalutx), nowadays 800 m above the modern-day sea level, as a consequence of the folding and elevation of the rocks during the formation of the Tramuntana mountain ranges.
The fossils from that deposit show that the dominant vegetation was composed by taxa typical of warm climates, similar to those found in the lakes of the late Eocene-early Oligocene, but some representatives of more temperate climates were also present. Together with palm trees (Sabal and Phoenicites), there are also reeds (Phragmites), willows (Salix), bayberries (Myrica), laurels (Laurus), avocados (Persea), breeches (Fagus), walnut trees (Juglans), oaks (Quercus), ash trees (Fraxinus), oleanders (Nerium) and mastics (Pistacia). The plant assemblage from Collet de Bini suggests a palaeoenvironment with remains of subtropical vegetation but with a trend towards an increasing temperate and Mediterranean climate.
The fossils from that deposit show that the dominant vegetation was composed by taxa typical of warm climates, similar to those found in the lakes of the late Eocene-early Oligocene, but some representatives of more temperate climates were also present. Together with palm trees (Sabal and Phoenicites), there are also reeds (Phragmites), willows (Salix), bayberries (Myrica), laurels (Laurus), avocados (Persea), breeches (Fagus), walnut trees (Juglans), oaks (Quercus), ash trees (Fraxinus), oleanders (Nerium) and mastics (Pistacia). The plant assemblage from Collet de Bini suggests a palaeoenvironment with remains of subtropical vegetation but with a trend towards an increasing temperate and Mediterranean climate.
The palaeoenvironments of the Balearic Islands were, during most of the middle Miocene, characterised by the existence of closed bays in which there was a high biological diversity. The faunal assemblage was probably similar to those in present-day warm coral seas of the Caribbean, with important coral reefs. An interior seaway stretched from the south of Menorca to Ibiza. During that time, “marès” (white calcarenites and limestones) deposits were formed, preserving a rich fauna of corals, molluscs, fishes and marine mammals.
During the Miocene, one of the largest marine predators of all time lived in the seas of Europe, Africa and America: the great shark Carcharodon megalodon. This shark, relative of the modern great white shark Carcharodon carcharias, reached lengths between 15 and 23 m, four times more than its modern-day counterpart. It is unclear whether Carcharodon megalodon is actually related to modern great whites; for this reason, some scientists classify those fossils into the genus Carcharocles. Just like Carcharodon carcharias, C. megalodon probably fed on large marine mammals, without disregarding fish schools. In the Balearic Islands, their large, triangular, serrated teeth, reaching heights of 20 cm, have been found in the white Tortonian limestones of the centre and east of the island. This large shark coexisted with the sirenian Halianassa cuvieri, of about three metres long, which could have been one of its preferred meals.
Fish fossil remains are frequent in the Tortonian deposits of Mallorca, which are usually made up of molasses, popularly known as “marès blanc”, and commonly used in construction works. The assemblage corresponds, especially in the centre of the island, to a neritic environment (close to the coast), with representation of genera of present-day groups such as wrasses (Labrodon and other related taxa), parrotfishes (Scarus), triggerfishes (Balistes), rays (Aetobates and Myliobatis), sparids (annular sea bream, common sea bream, gilthead bream and similar taxa such as Sparus and Diplodus) and sharks. This assemblage suggests a tropical climate, with forms typical of warm seas with coral reefs (such as parrotfishes, specialised in gnawing corals) with the presence of predators such as Carcharodon (white sharks), Odontaspis and Carcharias (bull sharks). Worth mentioning are the fossils of the genus Taurinichthys, which actually correspond to lower jaw teeth of the parrotfishes of the genus Scarus (such as Scarus miocenicus), nowadays present in most tropical seas.
During the Messinian (late Miocene), about 6 million years ago, the Mediterranean became disconnected from the Atlantic Ocean, causing a key event in the geological history of the Balearic Islands: a very important desiccation of the Mediterranean Sea. It is thought that this important event took place in a short period of time, probably no higher than 3,000 years, because temperatures were high during that time and the Mediterranean was, just like today, a sea with low continental water input. As a result of that desiccation, almost all the Mediterranean Tertiary marine fauna was wiped out, and most of the areas once occupied by the sea became a desert. In the deepest zones of the basin, there remained small saline seas such as the modern Dead Sea. However, the low sea level produced vast emerged areas between the Balearic Islands and the European continent, facilitating the conquest of the islands by species from the mainland. The terrestrial faunas that colonised the Balearic Islands during the Messinian probably were the ancestors of the faunas found by the first humans that arrived to the islands.
During the early Pliocene, about 5 million years ago, the Atlantic waters had already filled up the Mediterranean back again, isolating the Balearic Islands from the mainland. This isolation, which persists today, had an effect on the fauna and flora, evolving separately under island conditions. Over the Pliocene, an important climate change thawed most Antarctic ice and caused a sea level rise of more than 60 m above the present-day level. About 2 million years ago, the ice sheets started advancing again, and the Earth entered an increasingly colder phase with a glaciation affecting both hemispheres (called Donau-Günz glaciation). In the Balearic Islands, Mallorca was already populated by a very particular terrestrial vertebrate fauna, consisting of the artiodactyls Myotragus pepgonellae (middle Pliocene) and Myotragus antiquus (late Pliocene), ancestors of the famous Myotragus balearicus.
During the early Pliocene, about 5 million years ago, the Atlantic waters had already filled up the Mediterranean back again, isolating the Balearic Islands from the mainland. This isolation, which persists today, had an effect on the fauna and flora, evolving separately under island conditions. Over the Pliocene, an important climate change thawed most Antarctic ice and caused a sea level rise of more than 60 m above the present-day level. About 2 million years ago, the ice sheets started advancing again, and the Earth entered an increasingly colder phase with a glaciation affecting both hemispheres (called Donau-Günz glaciation). In the Balearic Islands, Mallorca was already populated by a very particular terrestrial vertebrate fauna, consisting of the artiodactyls Myotragus pepgonellae (middle Pliocene) and Myotragus antiquus (late Pliocene), ancestors of the famous Myotragus balearicus.
The Quaternary is the most recent of the geological periods, divided into the Pleistocene (from 1.8 million years ago to about 10,000 years ago) and the Holocene (reaching modern times). The Quaternary was an era characterised by the alternation of cold, glacial phases with temperate, warm phases. During the Pleistocene, there were important global events, such as the first appearance of our species. “Megafaunas”, formed by large mammals, nowadays extinct, dominated all the continents except for Australia, and culminated in key episodes such as the faunal exchange between South and North America, which had been isolated until then. It is thought that, at least four glaciations (named Günz, Mindel, Riss and Würm) have occurred during the Quaternary, with interglacial periods in between. A quarter of the Earth’s surface was covered by ice during the glacial periods.
The Quaternary in the Balearic Islands. By the end of the Miocene, the Gymnesic Islands (Mallorca and Menorca) became definitely separated from the Pithyusic Islands (Ibiza and Formentera). The surface of the islands underwent notable changes during the Pleistocene because of the great sea level changed caused by glaciations (with variations ranging from 130 m below present-day sea level during the coldest periods and 90 m above sea level in the warmer periods). During the maximum lowstand, there were two main islands: one formed by Ibiza and Formentera (occupying an area three times larger than the two islands today) and one formed by Mallorca and Menorca, extending south and also including the Cabrera sub-archipelago and a great part of the modern continental platforms. This island occupied an area two times larger than the present-day Mallorca and Menorca together.
The Quaternary in the Balearic Islands. By the end of the Miocene, the Gymnesic Islands (Mallorca and Menorca) became definitely separated from the Pithyusic Islands (Ibiza and Formentera). The surface of the islands underwent notable changes during the Pleistocene because of the great sea level changed caused by glaciations (with variations ranging from 130 m below present-day sea level during the coldest periods and 90 m above sea level in the warmer periods). During the maximum lowstand, there were two main islands: one formed by Ibiza and Formentera (occupying an area three times larger than the two islands today) and one formed by Mallorca and Menorca, extending south and also including the Cabrera sub-archipelago and a great part of the modern continental platforms. This island occupied an area two times larger than the present-day Mallorca and Menorca together.
The fossil beaches of the Balearic Islands (especially Mallorca) contain one of the most complete fossil records of the Mediterranean marine Pleistocene. This fauna, mostly composed of coastal and brackish molluscs, evidences the climate changes caused by the Quaternary glaciations, as well as the great sea level changes. These faunas are formed by more than 300 species, among which it is worth mentioning the taxa typical of warm periods. A large number of those species no longer live in the Mediterranean, but in the western coasts of Africa. Others have now found shelter in the warmer areas of the Mare Nostrum. During the last glaciation, some of those molluscs migrated to deeper waters, looking for more constant temperatures, and can still be found in the Balearic Islands.
During the Pliocene and Holocene, the vertebrate terrestrial fauna of the Balearic Islands was constituted by endemic species. Many of the animals that lived on the islands before the arrival of the first humans had evolved in isolation conditions, acquiring very particular anatomical traits related to height, vision, dentition and movement. It is thought that one of the factors that could influence these morphological particularities was the lack of predators. However, some raptor birds such as the giant barn owl (Tyto balearica) and the golden eagle (Aquila chrysaetos) probably preyed upon some of those animals, especially their new-borns.
Because of reasons still unknown, the particular mammal fauna from the Gymnesic islands never lived on the Pithyusic islands. On Ibiza and Formentera there was also an endemic fauna where mammals were completely missing (except for bats), consisting of an extraordinarily rich bird fauna with species that could have occupied the same ecological niches as mammals on Mallorca and Menorca, such as the Pithyusic goose (Anser sp.). On the Pithyusic Islands there was a giant tortoise as well.
Some of the endemic mammals from the Gymnesic Islands, such as Hypnomys morpheus and Nesiotites hidalgoi were gigantic compared to their closest mainland relatives. Meanwhile, the artiodactyl Myotragus balearicus was a dwarf among caprines, the smallest known both among extant and fossil species. From Menorca, a giant turtle and a hare have also been reported (Cheirogaster gymnesica and Nuralagus rex, respectively), which probably became extinct when the species from Mallorca entered the island during the latest Pliocene – early Pleistocene, about 2.3 million years ago. Almost all this particular fauna died out after the arrival of humans to the Balearic Islands. The lack of predators also facilitated that the vertebrate fauna, today surviving sheltered on the islets or in the karstic ravines of the Tramuntana ranges, such as the Balearic lizard (Podarcis lilfordi) of the “ferreret” (Alytes muletensis), lived without problems in many more places during the pre-human Pleistocene and Holocene.
During the Quaternary, the Balearic Islands probably constituted a refuge for the deciduous trees that disappeared from most areas of the continent during the glaciations. The last studies suggest that the beech (Fagus) was one of those refugeed species during the late Pleistocene and lower Holocene. During this last period, the vegetation was dominated by the box (Buxus). Moreover, deciduous tree communities such as hazelnut trees (Corylus), birch trees (Betula) and maple trees (Acer), were abundant in the Balearic Islands but are nowadays rare. During the late Holocene, already with human presence on the Islands, oleaster (Olea) was dominant.
The arrival of humans to the Balearic Islands had profound consequences on the endemic fauna that had remained isolated since the early Pliocene. The introduction of allochthonous species (domestic and wild), the changes on the natural vegetation and a possible hunting pressure (especially on Myotragus balearicus), have been suggested as the most probable causes of this extinction.
Among the present-day fauna and flora of the Balearic Islands, there remain some testimonies of the pre-human biota. The Balearic lizard (Podarcis lilfordi) and the “ferreret” (Alytes muletensis) are two of the survivors, although they suffer from habitat loss as time goes by. On the Pithyusic Islands, the endemic lizard Podarcis pityusensis did not suffer as much predator pressure, and today it can be found both on the islets and on the main islands. Other taxa are survivors of the Pleistocene or even previous times: among the flora, many endemic plants persist in the cliffs of the mountain ranges and, among the fauna, some endemic invertebrates live in the subterranean ecosystems of caves.
Among the present-day fauna and flora of the Balearic Islands, there remain some testimonies of the pre-human biota. The Balearic lizard (Podarcis lilfordi) and the “ferreret” (Alytes muletensis) are two of the survivors, although they suffer from habitat loss as time goes by. On the Pithyusic Islands, the endemic lizard Podarcis pityusensis did not suffer as much predator pressure, and today it can be found both on the islets and on the main islands. Other taxa are survivors of the Pleistocene or even previous times: among the flora, many endemic plants persist in the cliffs of the mountain ranges and, among the fauna, some endemic invertebrates live in the subterranean ecosystems of caves.
EXCEPTIONAL SITES. Of all fossiliferous deposits found on Earth, there is a special group (less than 100) that, because of the uniqueness and importance of their fossils, deserve a special status and protection, becoming paradigmatic examples in palaeontology. This places are known by the German name “fossil Konservat-lagerstätten”, applied to sites where the quality of its fossils is much more important than their abundance (“fossil Konzentrat-lagerstätten”). One of the main values of the “Konservat-lagerstätten” is that they usually preserve the remains of soft-body organisms that usually do not fossilise, or skeletons in anatomical connection or with remains of skin, fur, internal organs, etc. The good preservation of these fossils means that these deposits usually have more biotic diversity than what is usually preserved in the fossil record. On the other hand, in the “Konzentrat-lagerstätten” there are usually a lot of disarticulated skeletal remains with no fossilised soft body parts.
The main fossil deposits of the Balearic Islands
Geologists and palaeontologists have identified several zones and sites of palaeontological interest in the Balearic Islands. Some of these deposits no longer exist, either because they were ransacked or destroyed, or simply because they have disappeared due to natural causes (erosion, landslides, etc.) or artificial ones (residential areas, roads). They may also have been depleted because of uncontrolled and exaggerated collection by non-scientific collectors or traders. In any case, the fossils extracted preserved in scientific collections are testimonies to conserve. The heritage elements formed by the fossil sites and the fossils is irreplaceable and deserves the maximum protection.
The main fossil deposits of the Balearic Islands
Geologists and palaeontologists have identified several zones and sites of palaeontological interest in the Balearic Islands. Some of these deposits no longer exist, either because they were ransacked or destroyed, or simply because they have disappeared due to natural causes (erosion, landslides, etc.) or artificial ones (residential areas, roads). They may also have been depleted because of uncontrolled and exaggerated collection by non-scientific collectors or traders. In any case, the fossils extracted preserved in scientific collections are testimonies to conserve. The heritage elements formed by the fossil sites and the fossils is irreplaceable and deserves the maximum protection.