Spinosaurus

Spinosaurus ("spine lizard") is a genus of large, carnivorous theropod dinosaurs known from mid-Cretaceous Africa, with most material referred to the creature having come from Egypt and Morocco. They were among the largest theropod dinosaurs to have ever lived.

Description
The most notable feature of Spinosaurus was a row of tall spines that adorned its back, which are believed to have supported a sail in life, not unlike Ouranosaurus and the non-dinosaur Dimetrodon. It has been theorized that this "sail" would have been used for display purposes, to attract mates and intimidate rival spinosaurs.

Spinosaurus, like its relatives Baryonyx and Suchomimus, had sleek jaws like those of species of long snouted crocodilians (such as American crocodiles, orinoco crocodiles, African slender Snouted crocodiles, Australian freshwater crocodiles & False Gharials) and gharials, along with a long neck, both adaptions suited for seizing aquatic prey, which comprised a part of their diets (evidence exists that suggests spinosaurids also ate other animals, including pterosaurs and other dinosaurs). Also like Baryonyx and Suchomimus, it bore massive, hook-like claws on its hands.

Size
Spinosaurus is estimated to have been able to reach lengths of up to 15 - 16 meters (50 - 52 feet) from large specimens, making it the longest carnivorous dinosaur known, even longer than Tyrannosaurus and Giganotosaurus - some extreme estimates from prior to 2014 suggested that it could reach lengths of nearly 18 meters (60 feet). However, it was likely not as tall as the two creatures if its legs were as short as what was proposed by Ibrahim et al.. Modern estimates for the weight of larger Spinosaurus place them around 6.5 - 7.5 tons, lighter than some species other theropods of similar length. Earlier weight estimates range between 6 (lighter than most Tyrannosaurus estimates) and 23 short tons (exceedingly unlikely given how light the dinosaur's build was, and much heavier than all known predatory dinosaur estimates and some species of sauropods).

Legs
In 2014, material was described revealing that its legs were much shorter than those of its relatives, to such a degree that some have proposed that it was restricted to a quadrupedal gait when on land; others have suggested that it assumed a stance not unlike that of a pangolin. The find and the Spinosaurus specimen in question (named FSAC-KK 11888) have been questioned - some have proposed that the legs belong to a younger Spinosaurus than the rest of the specimen in the Ibrahim study (which would mean that it is chimeric, a mix of separate spinosaurs). Regardless of whether or not FSAC-KK 11888 is a chimera, Spinosaurus still would have had significantly proportionately shorter legs than its relatives in life.

Though many have suggested that this, combined with its webbed feet, were adaptations for swimming in deep water, a 2018 study on the buoyancy and aquatic capabilities of certain theropods, including Spinosaurus, suggests that, if its feet were not touching the floor of whatever body of water it was submersed in, it would have rolled over onto its side. This suggests that, instead of having a lifestyle revolving around swimming & diving in deep water, it would have spent most of its time in shallow water and/or on land, behaving more like a grizzly bear, a pelican or a heron; than a crocodile.