Spinosaurids have always been a hot topic of debate. For a long time, paleontologists doubted its aquatic life. Now that the fact is proven, the question turns to the hunting method of these giant theropods: did they swim chasing their prey or watch them from the surface, ready to spur them on with their long toothed crocodile snout? conical? An international team of paleontologists led by Matteo Fabri, of Natural History Museum Field of Chicago, therefore, went in search of general laws independent of any anatomical morphology, a common source of error. Your goal? Determine the distribution of aquatic adaptations in dinosaurs. To do this, the researchers relied on a possible relationship between bone density and aquatic ecology …
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Dinosaurs with dense bones for better diving
In 2014, a new skeleton of Spinosaurus is discovered on the rocky plateau of Kem Kem in Morocco. It has many characteristics of aquatic life, such as a spatula-shaped tail, which definitely confirms the ecology of spinosaurids. But then a new question arose among the scientific community: How did these giant theropods hunt in this environment? To make a decision, Matteo Fabri and his colleagues have an idea that came to them by looking at the skeletal morphology of existing species, such as hippos and tapirs. In fact, the latter do not look like animals that spend most of their time in the water … and yet they do! Could it be that extinct species have been unfairly placed in a terrestrial habitat?
The aquatic preference of hippos and tapirs is betrayed by the density of their bones. More precisely, this feature seems to be strictly related to underwater swimming in shallow water. Thus, solid bones would facilitate diving, unlike hollow bones in the center – such as donuts – specific to terrestrial animals. Matteo Fabri’s team is beginning to collect as much bone data from current and extinct species as possible, in order to better clarify the relationship that may exist between the bone density and the aquatic environment of a species, and why not just a dinosaur …
Disparity in spinosaurids
Researchers are trying to include all the species for which data are available, with sometimes extreme ecologies. The base thus built includes sections of ribs and femurs of about 25,000 species! From a few grams to several tons on the scale, the diversity of terrestrial and aquatic animals is abundant: whales, mice, dinosaurs, penguins, mosasaurs, alligators … The relationship finally obtained by scientists is used in the case of spinosaurid fossils. Result: a significant bone density strongly inclined towards aquatic habits, which would later lead to other more advanced anatomical changes. At least in the case of Spinosaurus aegypticusin North Africa, i Baryonyx walkeriin Europe … Indeed, his cousin from Niger Suchomimus tenerensis shows more hollow bones, signs of a hunting method closer to that of our modern herons.
However, having full bones does not always attest to aquatic ecology. As proof, the elephants and rhinos of today – or the sauropods of the past – that rely on strong bones to support their imposing mass. But in the case of spinosaurids, the anatomical structures of aquatic life abound. Maybe they weren’t the only dinosaurs that favored water above the ground … Unfortunately, Matteo Fabri’s team didn’t have the samples needed for further study, but it wouldn’t take long. Case to follow.
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