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.
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 a long snouted crocodylians (such as orinoco crocodiles and Australian freshwater crocodiles), and a long neck, both adaptions suited for seizing fish, which comprised a part of their diets (though evidence exists that suggests spinosaurids ate other animals, like pterosaurs and other dinosaurs).
Spinosaurus, as it was commonly depicted prior to 2014
Though no claws referred to the genus Spinosaurus are yet known, it can be inferred from its relatives that it also bore massive, hook-like claws on its hands.
Size
Spinosaurus is estimated to have been nearly 15 - 15.6 meters (50 feet) long 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 shorter than the two creatures if its legs were as short as what was proposed by Ibrahim et al. (2014); and whether or not it was heavier is disputed, with weight estimates ranging between 7 (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 adaptions 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 in deep water, it would have spent most of its time in shallow water or on land, behaving far more like a grizzly bear or pelican than a crocodile.
In The Land Before Time
A Spinosaurus, or "sharptooth", appears in The Land Before Time XII: The Great Day of the Flyers, when Guido wakes up after sleepwalking and sleep-flying all night. It is portrayed as a terrestrial animal, and is referred to as a Sharptooth by the Land Before Time dinosaurs.
Two Spinosaurus briefly appear in "The Hermit of Black Rock". Both of them resemble the dinosaur that appeared in XII, albeit in a different color possibly due to brighter lighting conditions.
Trivia
The Spinosaurus featured in XII looks similar to the one seen in Jurassic Park III.
The Spinosaurus depicted in XII is very inaccurate, for multiple reasons:
It is depicted as a fast, agile runner. Though it is unclear whether or not the recent neotype described by Ibrahim et al. 2014 is valid, some paleontologists believe that, with the newly discovered short legs of the creature, it would likely have been rather slow on land.
Its skull is reminiscent of Suchomimus, lacking the real animal's nasal crest and the kink in its premaxilla (upper jaw).
Its nostrils are located on the tip of its snout, when they should be placed near its eyes.
It is, akin to the series' Allosaurus, depicted with only two fingers. Real life Spinosaurus had three fingers, likely with a large thumb.
Its sail is similar to that of a Dimetrodon, and lacks the recently discovered kink.
Finally, it is temporally misplaced. Spinosaurus lived from 112 to 97 million years ago, during the Albian and Cenomanian stages of the middle Cretaceous.
Spinosaurus, as it is depicted in The Land Before Time Animated Moviebook
Outside of The Great Day of the Flyers, Spinosaurus also makes a small appearance in The Land Before Time Animated Moviebook during a minigame, wherein it is depicted similarly to how it was often depicted in the late 1980's and early 1990's.
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