Spinosaurus bone density indicated life and hunting in water

(ORDO NEWS) — The controversy continues about the lifestyle of Spinosaurus: new data on their bone density confirmed that these giant predators were excellent swimmers.

Spinosaurus were large bipedal predators of the Cretaceous period that lived 100-150 million years ago. Perhaps even the largest in history: according to some reconstructions, they could weigh under 20 tons and gain a couple of meters more than the famous tyrannosaurs.

However, paleontologists are still trying to understand what kind of lifestyle Spinosaurus led and how they hunted.

Indeed, many features of Spinosaurus indicate adaptations for swimming, including short, muscular, densely boned legs for better buoyancy; narrow conical teeth, convenient for capturing fish, and even a sail on the back, which could well serve as a keel, stabilizing the position of the body in the water.

On the other hand, the notion that dinosaurs were exclusively land based is still strong, while other groups of reptiles such as mosasaurs and plesiosaurs dominated the seas of that time.

Nizar Ibrahim and his colleagues at the University of Portsmouth believe that Spinosaurus lived and hunted in the water. To further demonstrate this, scientists turned to computed tomography, collecting a vast array of data on the density of the ribs and femurs in almost 300 modern and extinct species of animals – aquatic and terrestrial.

This included Spinosaurus and their close relatives, representatives of other groups of dinosaurs, as well as pterosaurs, birds, crocodiles and marine mammals. The bone density for each species was compared with data on how much time it spends in the water.

Such work has shown that density can serve as a reliable indicator of the transition from walking to swimming and from terrestrial to aquatic lifestyles. In the absence of full fins and a suitable tail, movement in the water can be stabilized by additional mass in the lower body, which is what the denser bones are for.

They give enough control over swimming, even allowing you to hunt in the water. Therefore, land animals are characterized by less dense bones with large cavities, while those that spend time in water are compact, like those of Spinosaurus.

However, the discussion about their lifestyle is still far from being resolved. Many experts, agreeing with the ability of dinosaurs to swim quite dexterously, refuse to believe that reservoirs were their main habitat and hunting ground.

Hippopotamuses can be taken as an example of such an animal: they spend a considerable part of their time in water, and even the density of their femur bones is comparable to the “transition to swimming”, which Ibrahim et al. write about. However, they cannot be called aquatic predators. Perhaps this also applies to the long-extinct Spinosaurus.

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