Saltriovenator
Apparently the oldest discovered dinosaur in the world is from the Po Valley, in Italy.
Saltriovenator (whose name means "hunter of Saltrio") is an extinct genus of theropod dinosaur ceratosaurus that lived in the lower Jurassic about 198 million years ago, in Saltrio (Italy), a small town in the Varese region, in the early Jurassic (Sinemurian), a period immediately following the mass extinction that occurred 201 million years ago, after the Triassic.
The genus contains a single species, namely Saltriovenator zanellai, for a long time known "Saltriosaurus", a temporary name, proposed by Cristiano Dal Sasso, in the year 2000, following the discovery, in 1996, by Angelo Zanella in a fossil deposit near Saltrio (VA), from which it takes its name.
Although we do not have yet a complete skeleton, it is believed that Saltriovenator was a large bipedal carnivore similar to Ceratosaurus. The dimensions in fact are quite large: it was not yet fully grown, it was eight meters long with a skull of about 80 cm, but it was a predator weighing about a ton, when most of the other species were smaller.
The Saltriovenator predates the massive carnivorous dinosaurs from over 25 million years: it is the largest predatory dinosaur of the Lower Jurassic.
In the summer of 1996, an amateur fossil hunter and collaborator of the Natural History Museum of Milan, Antonio Zanella, noticed traces of fossil bones in some rock blocks in the Salnova quarry on the outskirts of Saltrio, in the province of Varese, towards the Swiss border. The quarry was known for providing the stones with which the La Scala theater in Milan, part of the Mole Antonelliana in Turin and the Colleoni chapel in Bergamo were made. Zanella reported the discovery to the Milan Museum, which organized a prospecting in the quarry and collected as many rock samples as possible. The blocks containing the bones were transported to Milan, where they were subjected to 1800 hours of bath in weak acid, which dissolving the carbonate matrix brought to light 132 more or less complete bone elements. The animal probably died on the shores of an ancient sea before its remains were swallowed by the waters.
The holotype represents 10% of the skeleton and includes: a tooth, some fragments of the dorsal ribs and shoulder blades, a well preserved but incomplete forcula, both partial humeri, metacarpus II, phalanges II-1, III-1, III -2, the ungual of the hand III, a proximal fibula, a distal tarsal III and distal tarsal IV. Saltriovenator's hand, endowed with four fingers and extreme mobility, as Andrea Cau states, "fills a void in the theropod evolutionary tree [demonstrating that] predatory dinosaurs have progressively lost their little and ring fingers, and have thus acquired the three-fingered hand, precursor of the bird wing".
In the following 20 years, part of is this fossil was mentioned in some popular texts, cited in some technical articles and exhibited at the Milan Museum, but it has never been the subject of an official study. Although the name "Saltriosaurus" online circles, the taxon name was never strictly or formally established.
However, in December 2018, Cristiano Dal Sasso, Simone Maganuco and Andrea Cau described the specimen published in the prestigious American magazine PeerJ, a point of reference for all paleontologyst, a new genus and species: Saltriovenator zanellai. The name of the genus, Saltrivenator comes from the Latin with venator which means "hunter", joined to the place where the fossil was found, ie Saltrio. The specific name, zanellai, is in honor of Angelo Zanella.
After the death of the animal, its skeletal remains were broken down by natural causes several times during fossilization, and in this juncture many bones were lost. Although the Saltriovenator was not an aquatic dinosaur, the environment in which its carcass settled was likely pelagic, judging by the associated ammonite fossils. The location where the fossil was found is also rich in crinoids, gastropods, bivalves, brachiopods and bryozoans (Lualdi, 1999).
The deposition of the fossils occurred on a slope between a shallow carbonate shelf and a deeper basin. Several scratches, grooves and streaks indicate that the carcass has also been subjected to necrophagia by marine invertebrates. Many dinosaur bones in fact have signs caused by different animals and are the first ever found on dinosaur remains.
The taxonomic classification of Saltriovenator is somewhat uncertain, and the only sure point is the fact that it is a Theropoda. Originally, Dal Sasso classified "Saltriosaurus" as a generic tetanide. He later considered its classification as an allosauroid more likely, although in both cases it would precede the other members of the clades by about 20-30 million years.
Benson also considered it a member of the Coelophysoidea, in his description of Magnosaurus. The presence of a forcula may suggest that Saltriovenator is a member of the Tetanurae, although forculae are also known in coelophysoids.
The official description document of the animal, in 2018, conducted a large phylogenetic analysis and pointed to Saltriovenator as a basal ceratosaurus, closely related to Berberosaurus.
The ammonites of the Saltrio Formation, in which Saltriovenator was found, allow us to date the formation to about half of the Sinemurian. The dinosaur probably lived in the emerged part of the carbonate shelf or in an area to the north-west, whose presence had never been established. The latter possibility was suggested by Lualdi (1999), who analyzed the local geology based on the presence of terrestrial plants and the contents of terrígeno (sands from igneous or metamorphic rocks exposed to sub-aerial erosion) in limestones. The known sedimentary flora is essentially represented by leaves and small branches of araucariacee and bennettitales, the typical flora of the early Mesozoic. However, the plants and sand (which is referred to are not very abundant) may have been transported by sea currents, according to the most current paleogeographic maps, the truly continental soils, during the Jurassic, closer were today's mountains of Sardinia and the Corsica.
The presence of large dinosaurs, carnivores and herbivores in various icnofacies of the Lower Jurassic (Hettangiano-Sinemuriano) in the province of Trento, about 160 km east of Saltrio, would allow to change the traditional vision of the paleoenvironments and paleogeography of the region, considered a tropical sea with small islands of the atoll type. The footprints and the tracks are preserved in tidal carbonates deposited in a relatively narrow carbonate platform flanked to the east and west by relatively deep sea basins. Large theropods such as the Saltriovenator could not live in a confined place like an atoll, but they needed large areas of land to provide food and fresh water. And their herbivorous prey needed a land with the necessary vegetation for their sustenance. The presence of volcanodontids, cetiosaurs, primitive sauropods, heterodontosaurids and Scelidosaurs has already been reported by the Noriglio Gray Limestone Formation.
It is more likely that the peri-Adriatic platforms functioned as temporary continental bridges connected with the Laurasia e il Gondwana in the center from Tethis, allowing migration between the two hemispheres and the colonization of local coastal habitats.
During marine tides, some of these lands have remained isolated, implying genetic mutations for the terrestrial faunas of the place, with typical biological consequences and insular dwarfism.
An obsolete reconstruction of Saltriovenator, portrayed as an allosauroid, is present at the Prehistory Park of Rivolta d'Adda (VA):
The Saltriovenator fossils are exhibited in the Civic Fossil Museum of Besano (VA), Italy.
Domain: Eukaryota
Kingdom: Animals
Phylum: Chordata
Class: Sauropsida
Superordine: Dinosauria
Suborder: Theropoda
Clade: Ceratosauria
Genus: Saltriovenator
