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The Oldest Ceratosaurianfrom the Lower Jurassic of Italy, Sheds Light on the Evolutio
Carnivora Profile: Saltriovenator zanellai

'Miracle' Dinosaur Whose Bones Survived Being Blown Up Discovered in Italian Alps

By Laura Geggel, Senior Writer | December 19, 2018 07:12am ET

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The newly identified dinosaur Saltriovenator zanellai was found in the Italian Alps.
Credit: Davide Bonadonna

Paleontologists have excavated a mighty meat-eating, four-fingered dinosaur from an unexpected spot: the Italian Alps.
The newly identified beast — dubbed Saltriovenator zanellai — lived about 200 million years ago, and it's the first-known Jurassic dinosaur discovered in Italy, the researchers said. It's also the oldest-known ceratosaurian, as well as the largest (it weighed 1 ton), predatory dinosaur known from the earliest part of the Jurassic.
S. zanellai's journey to fossilization and discovery thrilled scientists, who deduced that the dinosaur's body ended up in the sea, where marine critters nibbled on its bones before it was buried. Then, it was lifted up toward the heavens as the Alps began forming about 30 million years ago. 
"It is a miracle that it survived such a long chain of events: drifting away to the sea, then floating, sinking, being scavenged by marine animals, reworked by sea bottom currents, buried, uplifted within a mountain chain, and eventually blown up by human explosives," study lead researcher Cristiano Dal Sasso, a curator of vertebrate paleontology at the Milan Natural History Museum, told Live Science.
(The excavation was difficult because, previously, industrial workers had used dynamite to blow up the quarry, which broke the fossils into hundreds of pieces, the researchers said.)
Angelo Zanella, an amateur fossil hunter, discovered the bones in 1996 in a marble quarry near Saltrio, less than 50 miles (80 kilometers) northeast of Milan. Dal Sasso and his colleagues then scouted out the site, digging up more bones, many of which had feeding marks from ancient marine invertebrates (sea animals without a backbone).
These chew marks make S. zanellai one of the few dinosaur specimens showing signs of marine invertebrate scavenging. Another was the armored ankylosaur Aletopelta, whose remains were likely nibbled on by scavenging marine invertebrates that lived off the coast of what is now Southern California, according to a 1996 study in the Journal of Paleontology.

Four-finger salute

Many of the 132 S. zanellai bones were fragmented, but there was enough evidence to indicate that the dinosaur had four fingers. The oldest dinosaurs, such as Herrerasaurus, had five fingers. But all known ceratosaurs, including the newfound Saltriovenator, Limusaurus, Ceratosaurus and Eoabelisaurus, had four fingers.
"Somewhere on the evolutionary line to ceratosaurs, the fifth (outermost) digit (the "pinky") was lost, resulting in the four-fingered hand of ceratosaurs," Matthew Lamanna, an assistant curator of vertebrate paleontology at Carnegie Museum of Natural History in Pittsburgh, who wasn't involved with the study, told Live Science in an email.
Later, theropods (mostly carnivorous, bipedal dinosaurs, such as Tyrannosaurus rex) took this trend a step further by losing their fourth (or "ring") finger, leading to the three-fingered hands seen in theropods such as Allosaurus, Oviraptor and Velociraptor. Later, these three fingers gave rise to the bird wing, Lamanna said.
There was some debate over which finger these three-fingered theropods "lost," but "Saltriovenator helps to show that the three-fingered hand of these theropods was produced through loss of the fourth finger rather than the first (thumb)," Lamanna noted.

Huge carnivore

S. zanellai was large — about 26 feet (8 meters) long — but the subadult wasn't done growing yet, study co-researcher Simone Maganuco, a vertebrate paleontologist at the Milan Natural History Museum, said in a statement. 
"The evolutionary 'arms race' between stockier predatory and giant herbivorous dinosaurs, involving progressively larger species, had already begun 200 million of years ago," Maganuco said.
Three of S. zanellai's four fingers had powerful claws, which likely served as a terrible "weapon of war" during the dinosaur age, Dal Sasso added.
The dinosaur's scientific name (Saltriovenator zanellai) means "Zanella's Saltrio hunter." (In Latin, "venator" means hunter.)
The study was published online today (Dec. 19) in the journal PeerJ.

Journal Reference:
Cristiano Dal Sasso, Simone Maganuco and Andrea Cau. 2018. The Oldest Ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, Sheds Light on the Evolution of the Three-fingered Hand of Birds.   PeerJ. 6:e5976.  DOI: 10.7717/peerj.5976

The homology of the tridactyl hand of birds is a still debated subject, with both paleontological and developmental evidence used in support of alternative identity patterns in the avian fingers. With its simplified phalangeal morphology, the Late Jurassic ceratosaurian Limusaurus has been argued to support a II–III–IV digital identity in birds and a complex pattern of homeotic transformations in three-fingered (tetanuran) theropods. We report a new large-bodied theropod, Saltriovenator zanellai gen. et sp. nov., based on a partial skeleton from the marine Saltrio Formation (Sinemurian, lowermost Jurassic) of Lombardy (Northern Italy). Taphonomical analyses show bone bioerosion by marine invertebrates (first record for dinosaurian remains) and suggest a complex history for the carcass before being deposited on a well-oxygenated and well-illuminated sea bottom. Saltriovenator shows a mosaic of features seen in four-fingered theropods and in basal tetanurans. Phylogenetic analysis supports sister taxon relationships between the new Italian theropod and the younger Early Jurassic Berberosaurus from Morocco, in a lineage which is the basalmost of Ceratosauria. Compared to the atrophied hand of later members of Ceratosauria, Saltriovenator demonstrates that a fully functional hand, well-adapted for struggling and grasping, was primitively present in ceratosaurians. Ancestral state reconstruction along the avian stem supports 2-3-4-1-X and 2-3-4-0-X as the manual phalangeal formulae at the roots of Ceratosauria and Tetanurae, confirming the I–II–III pattern in the homology of the avian fingers. Accordingly, the peculiar hand of Limusaurus represents a derived condition restricted to late-diverging ceratosaurians and cannot help in elucidating the origin of the three-fingered condition of tetanurans. The evolution of the tridactyl hand of birds is explained by step-wise lateral simplification among non-tetanuran theropod dinosaurs, followed by a single primary axis shift from digit position 4 to 3 at the root of Tetanurae once the fourth finger was completely lost, which allowed independent losses of the vestigial fourth metacarpal among allosaurians, tyrannosauroids, and maniraptoromorphs. With an estimated body length of 7.5 m, Saltriovenator is the largest and most robust theropod from the Early Jurassic, pre-dating the occurrence in theropods of a body mass approaching 1,000 Kg by over 25 My. The radiation of larger and relatively stockier averostran theropods earlier than previously known may represent one of the factors that ignited the trend toward gigantism in Early Jurassic sauropods.
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