Spinosaurus aegyptiacus Had Aquatic Lifestyle, Fossil Discovery Confirms

Spinosaurus aegyptiacus Had Aquatic Lifestyle, Fossil Discovery Confirms
The remarkably high abundance of the teeth of the giant dinosaur Spinosaurus aegyptiacus, compared to the dental remains of terrestrial dinosaurs and some aquatic animals, in the Cretaceous-period Kem Kem river system in Morocco strongly supports this 15-m-long predator being a largely aquatic animal spending much of its life in water where its teeth were shed and preserved.

The only known dinosaur adapted to life in water, Spinosaurus aegyptiacus swam the rivers of North Africa about 95 million years ago. Image credit: © Davide Bonadonna / National Geographic magazine.

The only known dinosaur adapted to life in water, Spinosaurus aegyptiacus swam the rivers of North Africa about 95 million years ago. Image credit: © Davide Bonadonna / National Geographic magazine.

Spinosaurus aegyptiacus is a giant theropod dinosaur that lived about 95 million years ago (Cretaceous period) in what is now North Africa.

This spectacular dinosaur has been interpreted as a fish-eating and semi-aquatic animal, and more recently shown to have possessed a highly modified tail suited for propelling the animal through water.

However, the hypothesis that this dinosaur was semi-aquatic — or even perhaps fully aquatic — has met with some opposition, not least because it challenges decade-old ideas on dinosaur ecology and evolution.

The discovery of hundreds of Spinosaurus aegyptiacus teeth at a new locality near Tarda on the northern margin of the Tafilalt in south-eastern Morocco further supports this hypothesis.

“The huge number of teeth we collected in the prehistoric river bed reveals that Spinosaurus aegyptiacus was there in huge numbers, accounting for 45% of the total dental remains,” said University of Portsmouth’s Professor David Martill, corresponding author of the study.

“We know of no other location where such a mass of dinosaur teeth have been found in bone-bearing rock.”

“The enhanced abundance of Spinosaurus aegyptiacus teeth, relative to other dinosaurs, is a reflection of their aquatic lifestyle.”

“An animal living much of its life in water is much more likely to contribute teeth to the river deposit than those dinosaurs that perhaps only visited the river for drinking and feeding along its banks.”

“From this research, we are able to confirm this location as the place where this gigantic dinosaur not only lived but also died. The results are fully consistent with the idea of a truly water-dwelling, ‘river monster’.”

Isolated vertebrate remains from two localities at Tarda, Morocco: (A) rostral denticle of Onchoprisits cf. numidus; (B) lamnid shark; (C) fragment of vomerine dentition from pycnodont; (D) unidentified large fish tooth; (E) lungfish dental plate; (F) tooth of abelisaurid; (G) tooth of indeterminate theropod; (H) tooth of Spinosaurus sp.; (I) tooth of Carcharodotosaurus sp.; (J) tooth of titanosauroid sauropod; (K) tooth of indeterminate ornithocheirid pterosaur; (L) tooth of pholidosaurid crocodile; (M) tooth of Elosuchus sp.; (N) fragment of dorsal fin spine of hybodont shark; (O) vertebra likely attributable to Onchopristis numidus; (P) fragment of indeterminate turtle carapace; (Q) teleost vertebra; (R) holostean scale; (S) indeterminate bone fragment. Scale bars - 10 mm. Image credit: Beevor et al, doi: 10.1016/j.cretres.2020.104627.

Isolated vertebrate remains from two localities at Tarda, Morocco: (A) rostral denticle of Onchoprisits cf. numidus; (B) lamnid shark; (C) fragment of vomerine dentition from pycnodont; (D) unidentified large fish tooth; (E) lungfish dental plate; (F) tooth of abelisaurid; (G) tooth of indeterminate theropod; (H) tooth of Spinosaurus sp.; (I) tooth of Carcharodotosaurus sp.; (J) tooth of titanosauroid sauropod; (K) tooth of indeterminate ornithocheirid pterosaur; (L) tooth of pholidosaurid crocodile; (M) tooth of Elosuchus sp.; (N) fragment of dorsal fin spine of hybodont shark; (O) vertebra likely attributable to Onchopristis numidus; (P) fragment of indeterminate turtle carapace; (Q) teleost vertebra; (R) holostean scale; (S) indeterminate bone fragment. Scale bars – 10 mm. Image credit: Beevor et al, doi: 10.1016/j.cretres.2020.104627.

“After preparing all the fossils, we then assessed each one in turn,” added study co-author Aaron Quigley, a Masters student at the University of Portsmouth.

“The teeth of Spinosaurus aegyptiacus have a distinct surface. They have a smooth round cross section which glints when held up to the light.”

“We sorted all 1,200 teeth into species and then literally counted them all up. 45% of our total find were Spinosaurus aegyptiacus teeth.”

“The Kem Kem river beds are an amazing source of Spinosaurus aegyptiacus remains,” added study first author Thomas Beevor, a Masters student at the University of Portsmouth.

“They also preserve the remains of many other Cretaceous creatures including sawfish, coelacanths, crocodiles, flying reptiles and other land-living dinosaurs.”

“With such an abundance of Spinosaurus aegyptiacus teeth, it is highly likely that this animal was living mostly within the river rather than along its banks.”

The study was published in the journal Cretaceous Research.

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Thomas Beevor et al. 2021. Taphonomic evidence supports an aquatic lifestyle for Spinosaurus. Cretaceous Research 117: 104627; doi: 10.1016/j.cretres.2020.104627

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