Oldest giant predator dinosaur discovered

Fossil discovered in northern Italy proves to be an important link in dinosaur evolution

Almost eight meters long and well over a ton: The predator dinosaur Saltriovenator zanellai was a real giant in his lifetime. © Davide Bonadonna, Gabriele Bindellini
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Sensational find: Paleontologists have discovered in northern Italy the oldest predator of the great predator dinosaurs - the largest carnivore of the early Jurassic. The fossil of the Saltriovenator zanellai baptized species is almost eight meters long, during his lifetime this giant probably weighed a ton. The fossil sheds new light on the size development of the predatory dinosaurs, but is also an important link to bird evolution.

Whether Tyrannosaurus rex, Allosaurus or Megalosaurus: These two-legged predator dinosaurs are among the largest representatives of the carnivorous prehistoric lizards. They were up to 15 feet long and weighed more than a ton. Even gigantic herbivores such as Brachiosaurus or Brontosaurus were therefore not safe from these predators. So far, however, it was unclear when the gigantic growth of carnivorous theropods began.

Forget about it in the museum cellar

Now a fossil from Lombardy in Northern Italy sheds new light on the evolution of the great predatory dinosaurs. The approximately 200 million year old relic was discovered as early as 1996 in a quarry north of Milan. However, because the fossil was deeply embedded in the rock, it remained initially for years undisturbed in the basement of the Milan Museum of Natural History.

Cristiano Dal Sasso with the bones of the Saltriovenator. Gabriele Bindellini

It was only in 1999 that the fossil was rediscovered, and researchers began releasing the dinosaur bones out of the rock with chemicals. However, because the fossil was highly fragmented, it took another eight years to assemble the skeleton. Only now it becomes clear what unusual find the Saltriovenator zanellai baptized dinosaur represents.

The biggest carnivore of his time

"Saltriovenator is the largest and heaviest thermopode of the early Jurassic, " according to Cristiano Dal Sasso of the Museum of Natural History in Milan and his colleagues. Because the fossil of this carnivorous dinosaur is 7.50 meters long and the animal was not even fully grown. "The analysis of the bones shows that Saltriovenator was a still growing cub, " says Sasso's colleague Simone Maganuco. "So his enormous size is all the more remarkable." Display

The paleontologists estimate that this predatory dinosaur must have weighed between 1.2 and 1.6 tonnes during his lifetime. "It shifts the emergence of theropods of this weight class by about 25 million years forward, " the researchers said. Because fossils of predatory dinosaurs from the early Jurassic are not only very rare, most of them are also much smaller than the Saltriovenator.

Size comparison Saltriovenator - Human. Marco Auditore

Ansto gigantism?

The early development of such large carnivores allows exciting conclusions about the ecology and prey-prey relationships in early Jurassic. Thus, even then a kind of "competition" between the robotic theropods and the herbivorous sauropods might have begun. In order to be prepared for the big carnivores, larger and larger forms of these dinosaurs developed in the course of this development.

"The proliferation of larger and relatively massive theropods at such an early stage was probably one of the factors that triggered the trend towards gigantism in sauropods, " say Dal Sasso and his colleagues.

Four fingers became three

Exciting, too: while the later predator dinosaurs carried only three fingers on their clawed front legs, the Saltriovenator still had four fingers. Only three of them, however, are strong and carry long claws. The fourth, outer finger is shortened. Thus, the fossil from the Italian Alps proves to be an important link in the theropod evolution letztlich and ultimately also for the development of the birds, as the researchers report.

"Saltriovenator sheds a new light on the evolution of the three-fingered hand of the birds, " explains Dal Sasso. For so far, it was disputed which finger bones correspond to their wing bones. While some paleontologists were more likely to suspect that the first finger - the "thumb" - disappeared among the ancestors of the birds, Saltriovenator now provides evidence for another scenario. Thus, the fourth finger of the theropods was first smaller and then completely reduced.

"The gripping hand of Saltriovenator fills a crucial gap in the family tree of theropods, " says co-author Andrea Cau from the Geology Museum on Bologna. "According to them, the predator dinosaurs gradually lost their little finger and then their ring finger. Out of the rest came the three-fingered hand, from which later the bird's wing emerged. "(PeerJ, 2018; doi: 10.7717 / peerj.5976)

Source: PeerJ

- Nadja Podbregar