Fossils: A look back to the past. Life in the Balearic Islands throughout all ages of the earth.
Nº 1. THE ENLIGHTENMENT
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.
Nº 2. EVIDENCE OF LIFE AND EVOLUTION
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).
Nº 3. THE PALAEOZOIC WORLD
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.
Nº 4. FERNS, THE DOMINANT VEGETATION
Nº 5. THE TRIASSIC, A CHANGING WORLD
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.
Nº 6. THE JURASSIC AND THE CRETACEOUS, THE EMPIRE OF THE REPTILES
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.
Nº 7. DOMINANCE OF THE SEA
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.
Nº 8. THE TERTIARY REVOLUTION
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.
Nº 9. THE FOSSILS OF THE COAL
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.
Nº 10. HALIANASSA CUVIERI
Nº 11. TOWARDS A MODERN WORLD
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.
Nº 12. RIVERBANKS AND FORESTS OF COLL DE BINI
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.
Nº 13. THE FISHES OF THE TORTONIAN
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.
Nº 14. FROM DESERT TO GLACIERS
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.
Nº 15. THE FINISHING TOUCHES
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.
Nº 16. THE COASTS AND MARSHES OF THE PLEISTOCENE
Nº 17. TERRESTRIAL FAUNA AND FLORA OF THE BALEARIC ISLANDS DURING THE QUATERNARY
Nº 18. CHANGES IN THE PARADISE
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.
Nº 19. FOSSILS, A NATURAL AND CULTURAL HERITAGE
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.