Lunedì Nov 20

Dinosaurs

Dominating the dinosaurs room is the skeleton of an Allosaurus fragilis, a large carnivorous dinosaur – a scary predator of a length of even more than ten metres. Its habitat was the Jurassic North America of approximately 150 million years ago. The panels provide a full account of the anatomic and behavioural characteristics of dinosaurs and their peculiarities, plus information on the latest discoveries and the most widely received theories concerning their extinction, about 65 million years ago.

Dinosaurs were the most successful of all reptiles during the Mesozoic era, lasting from approximately 250 to 65 million years ago. As opposed to most of today’s reptiles, such as crocodiles and lizards with their lateral limb arrangement, the legs of the dinosaur were straight, and were positioned below the body. The dinosaur’s greater agility and its success as an evolutionary development are due to this arrangement, made possible by a modification of the pelvis. Two panels describe the characteristics of these large reptiles.  Dinosaurs may be separated into two groups on the basis of the forms of the pelvis.

Saurischians have a reptilian pelvis, and Ornithiscians have a bird’s pelvis. Saurischians include Theropods, carnivores, and Sauropodomorphs, herbivores, which were enormous.

All Ornithiscians were herbivores, and they were endowed with spurs, armour and thorns as defence against predators. A panel describes the special characteristics of a group of fierce, and particularly efficient predators. This is the Dromaeosaurus, a fairly small dinosaur, capable of hunting in coordinated packs to kill even much larger victims. This hunting-pack theory was confirmed by the discovery of a group of 5 Dromaeosaurus fossils next to a fossil of a large herbivore. The most notable feature of these dinosaurs is the very large scythe like claw on the first digit of the foot, which sprang outward to lethally wound their prey.

Panels outline discoveries which, it is believed, definitively confirm the validity of certain recent theories, according to which some dinosaurs were probably warm-blooded animals. Birds may have evolved from small carnivorous dinosaurs. Many dinosaurs have been discovered in China with structures which are very similar to the plumage of birds. Dinosaurs capable of folding their forelimb toward the body, just as birds fold their wings, have been discovered in the Cretaceous sediments of Mongolia’s Gobi Desert.

The most important, and rare, discoveries made in Italy are illustrated in a panel. In the Veneto region and in southern Italy, many dinosaur footprints have been discovered on muddy land which then hardened and conserved the forms. DInosaur skeletons have also been extracted recently. The most famous is the small Scipionyx, nicknamed Ciro. Ciro was a Cretaceous carnivore. Its remains, discovered in the province of Benevento, include a full skeleton and some of the internal organs. A panel is dedicated to the many hypotheses that have been made in regard to the causes of extinction of these animals. According to one of the more widely credited hypotheses, the impact of an enormous meteorite striking the Earth some 65 million years ago brought about a series of catastrophes which wiped out many animal species, including dinosaurs.

One of the most well-known carnivorous dinosaurs is the Allosaurus. Most findings come from Jurassic deposits in the United States. The large Allosaurus fragilis skeleton in this room, too, is from the United States. It is about 150 million years old. The characteristically black bones are the result of the process of fossilization. The bones are also near-perfectly three-dimensional. Findings of this kind, in deposits containing vertebrates, are rare in our territory. As to its size, the Allosaurus may even reach a length of more than 10 metres. Furthermore, certain remains of the Allosaurus may indicate the presence of much larger animals resembling the Tyrannosaurus. In spite of appearances, the Allosaurus is not closely related to the well-known Tyrannosaurus rex, which belongs to the Cretaceous period, between 145 and 65 million years ago. The skull of T-rex was heavier. Generally larger and more bulky, one notable feature of T-rex was its tiny forelimbs with just two digits. The Allosaurus had better-proportioned forelimbs, with three digits. Skeletons tell us a lot about the life-styles of species. Given its sharp teeth and strong claws, the Allosaurus was clearly a fierce predator. Its skeletal structure is fairly light, hence the species’ name, fragilis. This suggests, despite its considerable size, that the species was fairly agile. The spine of this large carnivore biped remained parallel to the ground and its long tail provided an efficient counterweight, ensuring a balanced gait. The large skeleton exhibited here is a cast made from a specimen discovered in the United States. It was acquired in 1995, and was assembled by the museum’s staff over a period of about three months. The selected position is that of such a specimen as it walks slowly and cautiously - about 8 km per hour - on the lookout for prey.

Alloasurus Fragilis Alloasurus Fragilis Alloasurus Fragilis Alloasurus Fragilis Alloasurus Fragilis

A reconstructed Eryops occupies the niche above the entrance to the paleontology room. The Eryops was a North American amphibian of the Lower Permian era, dating back to about 280 million years ago. Its large, broad, flat head features the teeth of a predator. It fed on fish, small reptiles, amphibians and invertebrates. In all likelihood, its hunting technique is similar to that of today’s crocodile. Crocodiles lie in the water and await the next victim, with only their eyes and nostrils above the surface. While it frequented lakes and marshlands, it spent most of its time on solid ground. The robust body, of a length of up to two meters, was supported by short, sturdy legs. Thought not to have been particularly rapid in the water, it was one of the largest terrestrial animals of its period. The cast of a full Eryops skeleton can be found in the next room, dedicated to fossils.

A nest oviraptoridae
20 years after the Allosaurus exhibition, a new dinosaur will become the star for all the fans of the "terrible lizards."
After months of work "behind the scenes" the precious gift of the Museum of New York is displayed in the room dedicated to dinosaurs. This is the nest with a specimen of Citipati osmolskae, an oviraptoride lived in the Late Cretaceous.
The original fossil remains discovered in Mongolia return, as in a kind of freeze frame of about 70 million years ago, a particular moment of the life of this Citipati in a tipical position of hatching. The circular arrangement of the eggs and the upper limbs made protection of the nest, show the watchful care of this dinosaur so much so that the American researchers give to this exceptional finding the "Big Mama" nickname.