Spinosaurus aegyptiacus

Locomotion

• Spinosaurus was a semiaquatic animal that swam with its tail and hunted underwater.

  Evidence level: DisputedSources · 5

  One team argues its fin-like tail and dense bones made it an underwater pursuit predator. Other researchers modelled its body and found it would float and tip over, and argue it waded in shallow water like a heron. The question is open.

  Evidence for / against · 3

  Evidence for

  • Specimen · Spinosaurus paddle-like tail (FSAC-KK 11888)

    Tall, flexible tail with long neural spines and chevrons, interpreted as a fin for swimming.

    Specimen: FSAC-KK 11888

  • Histology · Dense limb bones in spinosaurids

    Bone cross-sections show very dense, compact limb bones in Spinosaurus and Baryonyx, like those of animals that dive.

    Specimen: FSAC-KK 11888

  Evidence against

  • Biomechanical model · Spinosaurus buoyancy and body models

    Digital body models finding Spinosaurus unstable and too buoyant to dive or pursue prey underwater; the tail too weak for fast swimming.

Posture

• Spinosaurus had short hind legs and may have walked on all fours on land.

  Evidence level: DisputedSources · 3

  The 2014 neotype reconstruction had very short legs, which suggested a four-legged gait on land. Critics say the skeleton may mix individuals of different sizes; later work by Sereno et al. (2022) reconstructs it as a biped.

  Evidence for / against · 2

  Evidence for

  • Specimen · Spinosaurus paddle-like tail (FSAC-KK 11888)

    Tall, flexible tail with long neural spines and chevrons, interpreted as a fin for swimming.

    Specimen: FSAC-KK 11888

  Evidence against

  • Biomechanical model · Spinosaurus buoyancy and body models

    Digital body models finding Spinosaurus unstable and too buoyant to dive or pursue prey underwater; the tail too weak for fast swimming.

Feeding

• Spinosaurus ate a lot of fish.

  Evidence level: Strong evidenceSources · 3

  Its long, narrow jaws and cone-shaped teeth resemble those of fish-eating crocodiles, and the chemistry of spinosaurid teeth suggests they spent time in water. Fish was very likely a large part of the diet, though it probably ate other prey too.

  Evidence for / against · 2

  Evidence for

  • Comparative anatomy · Spinosaurus conical teeth and long snout

    Straight conical teeth, interlocking rosette at the jaw tip and a long narrow snout, similar to fish-eating crocodilians.

    Specimen: MSNM V4047, BSPG 1912 VIII 19

  • Other · Spinosaurid tooth oxygen isotopes

    Oxygen isotope ratios of spinosaurid teeth closer to those of turtles and crocodiles than of other theropods.

Other

• The sail on the back of Spinosaurus was mainly for display.

  Evidence level: HypothesisSources · 2

  The sail, made of neural spines up to about 1.6 m tall, is well documented; its purpose is not. Display is the most common interpretation, but temperature control and other uses have been proposed, and there is no direct test.

Lived in: Kem Kem and Bahariya

100.5–93.9 million years ago · river system, delta, coastal plain, swamp / wetland

Cenomanian river systems and deltas along the northern edge of Africa, rich in large fish and crocodyliforms and remarkable for having several giant predatory theropods at once, with comparatively few herbivores preserved.