Gallery 002 · Hall of Spinosauridae
aegyptiacus, the sail-backed river giant
The largest predatory dinosaur ever found, and the strangest: a fish-eater the length of a bus that may have hunted in the water. This is its record, read straight from the bones.
Longest predatory dinosaur known
Sereno et al., 2022
Estimated body mass
≈7.4 t, Sereno et al., 2022
Tallest sail spines
Ibrahim et al., 2014
First bones found, Egypt
Named by Stromer, 1915
No other giant meat-eater was built like this. Uncover each feature to see why so many researchers read this skeleton as a river animal, and why the argument still runs.
Amber tick = a 1.8 m person, for scale
Uncover the anatomy
0 / 5 found
Since 2014, Spinosaurus has split the field. Everyone agrees it ate fish and lived at the water’s edge. The fight is over how deep it went.
Case for the swimmer
The deep, fin-shaped tail (Ibrahim et al., 2020), retracted nostrils and unusually dense bones (Fabbri et al., 2022) describe an animal shaped for active, tail-driven pursuit beneath the surface.
Case for the wader
Buoyancy and stability models (Henderson, 2018) and later studies (Hone & Holtz, 2021; Sereno et al., 2022) argue it would have bobbed and rolled in deep water, and likely hunted the shallows like a giant heron.
The settled part: conical teeth, a long snout and fish scales found with spinosaurid remains leave little doubt that fish were the main course. Only the diving is in dispute.
A 2022 study led by palaeontologist Paul Sereno put Spinosaurus aegyptiacus at about 14 metres long and 7.4 tonnes, still the longest predatory dinosaur ever found, ahead of both T. rex and Giganotosaurus.
In length, yes. Spinosaurus stretched to about 15 metres against roughly 12 metres for T. rex, though T. rex was heavier, more powerfully built and bit far harder.
Probably, at least in part. A deep, fin-like tail (described in 2020), unusually dense bones and a fish-catching snout all point to a life in and around water. Whether it actively swam after prey or waded and fished from the shoreline is still fiercely debated.
Mostly fish. Long jaws, straight conical teeth and pressure-sensing pits at the snout let it grip slippery prey in murky water, much like a crocodile, plus smaller prey and carrion.
No settled answer. Neural spines over 1.6 m tall, bound in skin, formed the sail. Display and species recognition lead the theories, with heat regulation and fat storage also proposed.
In North Africa, chiefly the Kem Kem beds of Morocco and the Bahariya Formation of Egypt, where Ernst Stromer unearthed the first bones in 1912 and named the animal in 1915.
Not a sprinter. Its short hind limbs suited wading and swimming rather than chasing prey across land, so it likely relied on ambush and quick bursts near the water.
During the Cenomanian age of the Cretaceous, roughly 99 to 93 million years ago, tens of millions of years before Tyrannosaurus rex ever appeared.
Specimen record
Spinosaurus aegyptiacus
“Spine lizard” · the sail-backed river giant
References
Peer-reviewed sources
