Lunedì Nov 20

Fossils, a world to discover

The room “Fossils, a world to be discovered” provides an overview of the evolution of our planet and of the fossils which have enabled a reconstruction of the Earth’s history. The exhibition is divided into four sections, each dedicated to the key themes of paleontology and the study of fossils, evolution and the systematics of invertebrates, vertebrates and plants. At the tactile exhibition areas, visitors can touch specimens that have turned to stone over time. The section also includes braille comments for the blind.

The main task of paleontologists is collecting, describing, classifying and deciphering fossils. Fossils are the remains and traces of ancient animal and plant organisms which have been preserved in rock strata. The section providing an introduction to paleontology, indicated by a purple colour, looks into the processes of fossilization, as well as rock dating, the study of fossils, and evolution of life forms. Cabinet 1 displays a number of findings from the world’s most important fossil deposits. With a tactile installation visitors can touch a rock with accumulated fossilized seashells. This original specimen, which is about 225 million years old, was discovered in the province of Bergamo. These genus Myophoria bivalve shellfish were deposited on an ancient seabed by currents. A tactile installation with drawers provides an account of the process of fossilization in a marine environment. In the first drawer we have conditions today, with some fish and molluscs lying on the sandy seabed. The second drawer illustrates conditions some years later. The shells have lost their original colour; the currents have broken the shells and have accumulated the more resistant elements. The fish tissues have decomposed, and the various parts of the skeleton have been scattered. In the third drawer, we find what has happened some after millions of years. The sand on the seabed has turned to stone. On the surface layer the shells have dissolved, leaving only their impression or ‘footprint’. Ina cabinet is contained two extremely valuable fossils, with some of the original material constituting the shell, i.e. mother-of-pearl for Acanthohoplites and aragonite for Asteroceras. Many visitors wonder about the processes of collecting and preparing fossils. Answers are given in cabinet 8. An example is provided of the work carried out by the museum’s own research staff on bear remains found in a cave in the province of Bergamo. When collecting fossils, information is also obtained on the precise location of the findings. All details are recorded in a working log. The material is cleaned very carefully at the museum. The fossils are restored and repaired, entered into a catalogue, studied, and either stored or exhibited.

Three tactile installations with casts and original fossils have been placed under the windows to the rear of the room dedicated to systematic paleontology. At the first installation, visitors will have a chance to touch a cast of the left mandible of a young cave bear and the large triangular tooth of a shark dating back some four million years. Sharks leave behind them only their teeth. The shark’s skeleton is made up of cartilage, so fossils are very rare. Visitors will also have a chance to touch a claw of the lethal Allosaurus, one of the Earth’s largest carnivorous dinosaurs, as well as the trilobite, an animal which became extinct during Paleozoic era. It is known as the trilobite because its body is divided into three lobes. Mankind’s belief that fossils are endowed with medicinal and supernatural properties dates back more than 10,000 years. The second installation features fossil casts and original fossils which, over the centuries, have given rise to many legends. The exhibit includes a section with the original shell of a Conchodon. Due to its odd shape, according to a longstanding folk tradition, it was believed to be a footprint of the devil. The last of the three tactile exhibition installations hosts the cast of a Lariosaurus fossil. The Lariosaurus is a Middle Triassic reptile, notable for its long neck and skull, particularly suited to its aquatic habitat.

Invertebrates represent the first life forms appearing in primordial seas and dominating from the Precambrian era until the Paleozoic era, and most of the Earth’s animals still belong to this category. Remarkable for their size are the two rudistid fossils exhibited. These rudistids, of the genus Hippurites, were bivalve mollusc reef-builders, now extinct, characterised by a markedly asymmetric shell. The same cabinet also features an Inoceramus specimen from the hills around Bergamo. It was discovered at a stone quarry for wall building material on Monte Bastia. A cabinet hosts gastropod fossils of the genus Gigantonia, originating in the province of Bergamo. Because some of the original colour has been preserved, the specimen on the wall is of enormous scientific interest. Please note the remarkable size of this group of shells. Cabinet 15 hosts a rock sample with many Promicroceras specimens in which the original material of the shell has been preserved (in this case, aragonite). The rock sample comes from the English deposit of Lyme Regis, a famous geological park on the English Channel. The Leptotheuthis specimen in the same cabinet shows that these animals could reach considerable sizes. Many ammonite specimens are featured . Ammonites are extinct molluscs belonging to the cephalopod group. Today’s octopus, the cuttlefish and the squid belong to this group. Only the Nautilus remains to bear witness to this extinct life form. The Nautilus – a truly splendid marine organism – is, in effect, a living fossil. It can still be found in the deep waters of the western Pacific Ocean. The ammonite’s shell was divided into various chambers. The animal itself inhabited only the outer chamber. When it needed to sink to a lower level , the ammonite would let water enter the shell to weigh it down. To rise to the surface again, the shell was emptied by emission of a gas so that it could then float upward along the water column. The most striking finding on display here, given its size, contains specimens of the genus Dactylioceras. After millions of years of evolution, ammonites also developed uncoiled forms, as can be seen in the Agoniatites specimen. The cabinet also contains a number of Belemnoidea specimens, which also belong to the cephalopod molluscs class, such as ammonites, but they are characterised by an inner shell.

A section deals with the evolutionary history of the vertebrate classes. The first vertebrates were fish. Differentiation dates back as far as the Paleozoic era. Later colonization of the dry land by amphibians was made possible by substantial modifications of the limbs, spinal column and respiratory apparatus. Amphibians gave rise to Reptiles, such as dinosaurs, which ruled over practically the entire Mesozoic era. The major new evolutionary characteristic presented by reptiles was their amniotic egg. This is an egg with a shell to protect the young from the stresses of collision, while also providing a shield against dehydration. Eggs could, for the first time, be laid away from the water. Another new development of the Mesozoic era was the bird – the world’s first warm-blooded animals. The next era, the Cenozoic era, witnessed the extinction of the dinosaur and spread of mammals. A cabinet features many fish fossils, including a perfectly preserved specimen from the Tertiary deposit at Bolca, in the province of Verona. The location is one of the most important and rich deposits in the world for fossils from the Middle Eocene epoch, dating back some 50 million years. At the dawn of the Tertiary era, the area now known as Bolca was a large costal lagoon with a series of shallow basins filled with calm, very salty water, closed off by coral atolls. The climate, vegetation and fauna were typical of a tropical marine environment. Certain natural phenomena, still not fully understood, such as volcanic eruptions or the development of exceptionally large quantities of plankton, caused fish to die in the open sea. The fish were transported to the basins, where they settled on the floor, then to be covered by a very fine sand in which they were fossilized together with the remains of plants, flowers, fruits and other animals such as the turtles and crocodiles which lived on the surrounding small islands. Cabinet 21 contains rock samples preserving the footprints of amphibians dating back to the Permian period. On its surface, the sample on the wall features relief footprints of the Amphisauropus. A cabinet  features the cast of a full skeleton of Eryops megacephalus – a large Paleozoic amphibian. Here, visitors will learn about the complex process of modification undergone by the limbs of vertebrates during the transition from life under the water to life on dry land. The fins of the fish - delicate structures suitable for swimming evolved into the sturdy limbs of tetrapods, strengthened by the presence of bones and linked to the spinal column to form legs capable of supporting weights during locomotion.

Amother section of the room is dedicated to fossilized plants. Here we have a record of the evolution of vegetation from one geological era to the next. Plants were the first life forms to emerge from the water and to colonise dry land. Thanks to the presence of plants, other life forms were then also able to colonise the land. The exhibits in this part of the room have been ordered on the basis of the manner in which the fossils have been preserved. For plants, the most likely component to be found in fossil form is the trunk, and cabinet 29 presents many samples from various species, all dating back to the Carboniferous period, more than 300 million years ago. Cabinet 30 features, instead, branches and fruits. Compared to trunks these elements are less likely to be preserved as fossils. The Proaraucaria specimen is of particular interest. This very ancient plant belongs to a family which has survived to this day in the southern hemisphere. A cabinet features the fossilized flora of Monte Pora. The Museum’s research work on this deposit of the Bergamo district focused on Triassic findings dating back to the Carnian period, some 230 million years ago. Researchers have identified 23 species, some of which belong to groups still with us today. Others belong to extinct groups. The Porastrobus specimen on display is a holotype. Holotypes are specimens that enable the defining of a new species. .

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