Spinosaurus

Spinosaurus was a very large predatory theropod from North Africa during the Cenomanian stage of the Late Cretaceous, about 100–95 million years ago. Secure fossils come from Egypt, Morocco and Niger. Long fish-catching jaws, tall vertebral spines, shortened hind limbs in S. aegyptiacus and a deep tail created a body unlike that of any completely known large theropod.

There is no complete skeleton. The original Egyptian specimen was destroyed, Moroccan material joins bones from an incomplete individual, and many additional fossils are isolated. Every full-body reconstruction fills gaps with related spinosaurids and assumptions. That is why the outline has changed repeatedly and why confident claims about swimming require care.

Quick facts

The Egyptian discovery and a lost holotype

Fossil collector Richard Markgraf found a partial large theropod skeleton in Egypt’s Bahariya Oasis in 1912. Ernst Stromer named Spinosaurus aegyptiacus in 1915. The holotype included parts of the lower jaw, teeth, neck and back vertebrae, ribs and gastralia. One neural spine stood about 1.65 metres high.

The specimen was stored in Munich and destroyed during an air raid in April 1944. Stromer’s descriptions, drawings and photographs remain, but the original bones cannot be scanned or compared using modern techniques. Later fossils must therefore be related to an incomplete historical record.

FSAC-KK 11888 from Morocco, published in 2014 and expanded with tail material in 2020, preserves portions of the skull, spine, pelvis, limbs and much of the tail. It was proposed as a neotype, though both that designation and the association of all material have been debated. A type specimen anchors a scientific name, and replacing a lost one requires unusually strong justification.

Species and contested names

The recently verified Russian source recognises S. aegyptiacus and S. mirabilis. The latter was described in 2026 from the Farak Formation of Niger and is represented by immature individuals. Its low snout, more widely spaced rear teeth and very tall fused nasal crest distinguish the known material. The adult body size and final crest outline remain unknown.

S. maroccanus, named largely from neck-vertebra proportions, is commonly treated as doubtful or as a possible synonym of S. aegyptiacus. Some analyses retain Sigilmassasaurus from Morocco as a separate spinosaurine; others combine relevant material with Spinosaurus. The historical label “Spinosaurus B” is not a valid species name.

These disputes reflect isolated bones, mixed localities and animals of different sizes. They should not be hidden by treating every North African spinosaurid tooth as one species. The hierarchy of specimen, species, genus and family is explained in dinosaur groups.

A body assembled from incomplete individuals

The original Egyptian skeleton was partial. A large Moroccan snout, MSNM V4047, adds jaw anatomy. FSAC-KK 11888 provides fragments of the head and several body regions. Other teeth, vertebrae and crests come from separate individuals and are not always identifiable to species.

The S. mirabilis holotype MNBH JEN1 contains much of the front of the upper jaws, part of the crest, a jaw margin and five teeth. Additional Niger material includes skull pieces, vertebrae and limb elements from several individuals. Museum and digital reconstructions are scientifically useful composites, not discoveries of one intact animal.

Size without false precision

Old estimates of 17–18 metres scaled isolated bones too directly. Large S. aegyptiacus is more cautiously reconstructed at about 12–14 metres and broadly 5–8 tonnes. Torso length, muscle volume, respiratory spaces and the choice of specimen all affect the result.

The immature S. mirabilis holotype has been reconstructed at about 8 metres. It may have grown larger, but no adult skeleton provides a final number. Spinosaurus may have exceeded most Tyrannosaurus specimens in length while remaining lighter than the largest adults. The size comparison therefore avoids a single “largest predator” ranking.

Skull, teeth and diet

The skull was long and low. The snout widened at the tip and narrowed behind it, forming a rosette that helped retain prey. Small nostrils sat well back from the tip. Conical teeth lacked the broad slicing form of allosaur or tyrannosaur teeth. Upper and lower tooth rows interlocked, creating an effective trap for slippery prey.

This anatomy strongly supports fish capture. Aquatic deposits and chemical signals in teeth reinforce the connection. No accepted stomach contents from the genus reveal its last meal, so an exclusively fish diet is not established. Opportunistic feeding on terrestrial prey or carrion remains possible.

Form, wear, isotopes and direct digestive remains provide different strengths of evidence. Their proper combination is described in reconstructing extinct diets and tooth-wear evidence.

The sail and the deep tail

Extremely tall neural spines supported a dorsal sail or ridge whose exact soft-tissue contour is not preserved. It may have acted in display, recognition or heat exchange, and it affected movement through water. None of these possibilities is proved as the sole function.

The deep tail described in 2020 could generate more thrust than the narrow tails of conventional terrestrial theropod models. That supports useful propulsion in water. It does not by itself show how long the animal swam, how deeply it submerged or whether the entire body remained stable during pursuit.

The crest of S. mirabilis strengthens the possibility that conspicuous structures carried visual signals. Colour and pattern still remain artistic because bone cannot preserve them. The boundary between fossil and reconstruction follows the same rules discussed for skin and colour.

Could Spinosaurus dive after fish?

Evidence for strong aquatic specialisation includes tooth isotopes, dense bones, reduced hind limbs and the deep tail. Tail models show potential thrust, while bone compactness has been interpreted as ballast for underwater feeding.

Other studies find a highly buoyant and unstable body, drag from the sail and no flippers or compact limbs comparable to fully aquatic vertebrates. The statistical link between bone density and diving has also been challenged. S. mirabilis retained a hollow shin and relatively longer lower leg, and its inland river setting shows that the genus was not restricted to marine coasts.

The secure minimum is clear: Spinosaurus was strongly associated with water, caught aquatic prey and could swim. Regular deep diving and prolonged underwater pursuit remain hypotheses. A large biped wading and striking in rivers and shallows fits all direct evidence without claiming more than the fossils show.

Movement on land

The small pelvis and shortened hind limbs of S. aegyptiacus produced unusual proportions. They do not demonstrate habitual quadrupedal walking. The hands lack the weight-bearing specialisations of a dedicated quadruped, and later centre-of-mass models permit bipedal support.

It was probably less efficient at sustained terrestrial pursuit than similarly sized land predators. Exact walking speed, resting posture and transitions between water and land depend on missing joints and muscles.

North African habitats

Egyptian and Moroccan fossils occur in deposits of rivers, deltas, lagoons and coastal plains that supported large bony fish, sawfish relatives, sharks, crocodile relatives, turtles, pterosaurs and other dinosaurs. Niger material comes from an inland river basin hundreds of kilometres from the contemporary sea.

These environments explain the repeated association with aquatic prey without turning the animal into a marine reptile. Living near water, swimming and pursuing prey underwater are three different claims requiring different evidence.

Evidence, inference and reconstruction