During their grand Mesozoic heyday, dinosaurs didn’t live in the ocean. Every young aficionado on the terrible lizards knows this, quick to correct their parents or teachers should an adult mistakenly call a plesiosaur or mosasaur a dinosaur. And yet, sometimes non-avian dinosaurs are found buried in marine sediments, and the latest example of a dinosaur found sleeping with the fishes, as it were, is Saltriovenator zanellai.
Paleontologists Cristiano Dal Sasso, Simone Maganuco, and Andrea Cau named the Jurassic carnivore earlier this month. A total of 132 skeletal pieces, found close together, formed the basis of the description, representing a theropod dinosaur never before seen. But that's hardly all.
At over 24 feet long and about 198 million years old, Saltriovenator is now the largest known carnivorous dinosaur from the Early Jurassic. Dal Sasso and colleagues propose the evolution of predators as large as their new theropod may have fueled any evolutionary arms race that nudged herbivores - such as the long-necked sauropodomorphs - to get larger in short order as a form of defense. Not to mention that the hand anatomy of Saltriovenator helps establish the anatomical foundation of theropod hands that would eventually become the basis for what’s seen in the wings of modern birds. But there’s something else about this theropod that has never been seen before.
Dinosaurs that were inadvertently washed out to sea and buried have been found here and there. The sauropod Austrosaurus, for example, ended up in such a setting, just as the spectacularly-preserved ankylosaur Borealopelta. Another armored dinosaur, Aletopelta, was preserved on the sea bottom long enough to briefly be home to a small-scale reef after death. But the remains of Saltriovenator, Dal Sasso and coauthors write, is the first known instance of marine invertebrates eating away at a dinosaur.
At a glance, Saltriovenator might look like a bit of a mess. The dinosaur’s bones were disarticulated, jumbled, and even broken into fragments. Yet most of the anatomical pieces were not deformed postmortem, and maintained their shape. These clues, and others, come together to outline what happened to this carnivore just as dinosaurs were gaining global dominance.
The likely sequence of events, the paleontologists write, is that the dinosaur’s carcass floated to sea, sunk, decayed, became disarticulated, and then the bones were exposed for a long time before their final burial. At least 30 pockmarks in the bones seem to back up the scenario. The holes vary in size and shape, the researchers note, but they are consistent with what’s been seen on other seabottom skeletons. These holes were made by marine invertebrates that lived in the shallows and bored into the bones, making this the first time such damage has been seen on a dinosaur. It’s likely that more than one species damaged the bones, and, even though the exact species that consumed the bones aren’t known, it still tells part of this dinosaur’s story. Saltriovenator didn’t just have a life. It had a particularly interesting afterlife.