Spinosaurus was one of the largest carnivorous dinosaurs ever discovered. They look like T. rex, but with a long, narrow snout and short legs. Originally discovered in 1915, it includes species like Spinosaurus from North Africa and Baryonyx from England. They weigh around 7 tons, with a large crest-shaped sail on their backs.
A recent study by a multi-agency team, including the Field Museum of Natural History in Chicago, the University of Oxford and the University of Cambridge, suggests that some dinosaurs of the spinosaurid family swam underwater at the search for prey.
Using an X-ray imaging technique on fossilized bones, scientists analyzed their bone density. They then compared the bone structure of living animals and birds that hunt in water. They demonstrated strong evidence that dinosaurs of the spinosaurid family swam underwater to search for prey.
Based on fossilized gut contents, spinosaurids were thought to be amphibious hunters, eating surf and turf. However, the subject of debate was whether they caught fish in the water like a crocodile or hunted in the shallows like a heron.
Given their long snouts and tail fins, some paleontologists believed spinosaurids to be specialized aquatic predators. But fossil footprints show that most dinosaurs walked on land, and evidence of swimming is sparse.
To solve this puzzle, the scientists in this study used data on skeletal bone density. Scientists have used CT scans to collect cross-sections of femurs and ribs from more than 200 living animals, including those that hunt in water like otters and those that feed on land like badgers. The data was then compared to many dinosaurs, including three spinosaurids: Spinosaurus, Baryonyx and Suchomimus.
The results showed that animals that submerge underwater to hunt for food have completely solid bones, while cross-sections of land dwellers’ bones look like donuts with hollow centers.
Co-author Professor Roger Benson, from the Department of Earth Sciences, University of Oxford, said: “Animals that forage for food underwater have high bone density to help them stay submerged without expending too much energy, including hippos, sea lions, cormorants and crocodiles.”
Lead author Dr. Matteo Fabbri, Field Museum of Natural History, Chicago, said: “We found a very strong correlation between bone density and underwater foraging. This means that all animals that have the behavior where they are completely submerged have these dense bones, and that was the good news because it allows us to test which dinosaurs swam underwater.
Spinosaurus and Baryonyx had dense bones associated with complete submergence, while their close relative Suchomimus had more hollow bones. It always lived near water and ate fish, as evidenced by its crocodile-like snout and conical teeth, but it did not swim to hunt due to its bone density.
Dr Fabbri noted, “One of the big surprises of this study was the rarity of underwater foraging for dinosaurs. We only found evidence of this in spinosaurids, and their behavior was much more diverse than we would expect. pensions.
“Dinosaurs are mysterious and inspiring animals, but we only have their bones, and most skeletons are incomplete. Our study shows how much more we could learn about dinosaurs using analysis of living animals. In the future, we expect this approach to continue to yield new insights into dinosaurs and their world.
- Fabbri, M., Navalon, G., Benson, RBJ et al. Underwater feeding in carnivorous dinosaurs. Nature (2022). DO I: 10.1038/s41586-022-04528-0