Anonim

Until a few decades ago, the discovery of a dinosaur in Italy was considered an impossible event. Our country, in the Mesozoic, was almost all under the waters of the ocean, and for this reason it was thought that the fossils were non-existent. Then came the discovery of Cyrus (Scipionyx samniticus), one of the best preserved fossils of all paleontology, and many others followed. The last one, announced on December 19, is a fossil of great importance: a dinosaur that has been called Saltriovenator zanellai (from the place of the discovery, a quarry near Saltrio, in the province of Varese, and from the name of who discovered it, Angelo Zanella). The article, written by three Italian palentologists, Cristiano Dal Sasso, Simone Maganuco and Andrea Cau, was published in the journal Peer j (here the original text, in English).

By the way: how did the velociraptors get so fast?

A little-known period. The discovery is exceptional for many reasons. First of all, for the period: Saltriovenator in fact lived about 198 million years ago, in the first Jurassic, a period immediately following the mass extinction that took place 201 million years ago, after the Triassic.

Image Reconstruction of the skeleton of the new dinosaur. The items found are highlighted in orange. The person used as a ladder is Angelo Zanella (1.67 tall), the one who found the skeleton. | Marco Auditore

In that era some dinosaurs, the so-called theropods, were - as they say technically - diversifying a lot. New species were born and evolved and populated new environments. The theropods were a group of predators of various sizes, with a bipedal gait and equipped with forelimbs with claws; to the group belonged famous species, like the Tyrannosaurus rex or Velociraptor, lived much later than the … newcomer.

Large carnivore. Some of the paw bones, hand and ribs were found of the new dinosaur, enough to reconstruct the fossil. Saltriovenator is also important for other reasons. The dimensions are quite large: it had not yet fully grown, but it was a heavy predator about a ton, when most of the other species were smaller. This means, as one of the authors of the text says, that "the evolutionary" arms race "between predators and herbivorous dinosaurs, which involves progressively larger species, had already begun 200 million years ago".

Image Simplified evolutionary tree of predatory dinosaurs (Theropods). The Saltriovenator precedes the massive carnivorous dinosaurs for over 25 million years: it is the largest predatory dinosaur of the lower Jurassic. |

Many dinosaur bones have signs caused by marine invertebrates; they are the first ever found on the remains of dinosaurs and tell the fate of the animal: the carcass floated in a sea basin and then, sunk, remained on the seabed for quite a long time.

The hands of birds. Another important detail for paleontology and above all for the history of birds is the structure of the hand, a highly debated detail concerning the descent of birds from dinosaurs (according to some hypotheses this descent is not true). The hand of Saltriovenator instead, as Andrea Cau states: "fills a void in the evolutionary tree of theropods [demonstrating that] the predatory dinosaurs have progressively lost the little finger and the ring finger, and have thus acquired the hand with three fingers, precursor of the 'wing of the birds'.