Ouranosaurus nigeriensis

Ouranosaurus nigeriensis was a distinctive iguanodontian herbivore from the Elrhaz Formation of Niger. Two unusually complete skeletons reveal a deep torso, powerful forelimbs, a broad duck-like beak and tall neural spines over the back and front of the tail. Those spines certainly supported expanded soft tissue, but fossils do not show whether the living outline was a thin display sail, a thick muscular and fatty ridge, or something between them. Ouranosaurus sits close to the evolutionary grade that produced duck-billed dinosaurs without itself being a true hadrosaurid.

Its fossils occur between approximately 125 and 112 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was low and broad at the muzzle, with a keratin-covered beak at the front and dense batteries of leaf-shaped cheek teeth farther back. Each hand had a conical thumb spike, three central weight-bearing digits and a mobile outer finger. Robust arms show that it could stand and walk on all fours, while the hind limbs and balancing tail also permitted bipedal movement. Neural spines over the trunk reached many times the height of their centra and continued onto the tail. Their thickened bases and ligament scars confirm substantial soft-tissue support but do not preserve its external shape.

• Tall neural spines along the back and front of the tail
• Broad keratin-covered beak and batteries of cheek teeth
• Conical thumb spikes on robust hands
• Three central weight-bearing fingers with hoof-like tips
• Powerful forelimbs supporting both quadrupedal and bipedal movement
• Deep ribcage with an unusually elongated torso profile

Philippe Taquet's French expedition found the first major skeleton, GDF 300, at Gadoufaoua in 1965. Taquet introduced the name informally before publishing the formal monographic description in 1976. A later French-Italian expedition recovered another nearly complete skeleton that became the celebrated Venice mount, now catalogued MSNVE 3714. Detailed re-examination in 2017 showed that this mount incorporates the original paratype GDF 381 and clarified which bones are genuine, reconstructed or from more than one individual. The species name refers to Niger, while Ourane is a Tuareg-derived word translated as brave or courageous.

Discovery credit: Philippe Taquet, French Gadoufaoua expedition.

Naming authors: Philippe Taquet.

Gadoufaoua lay on a low-relief Early Cretaceous floodplain crossed by rivers and dotted with lakes and wetlands. The Elrhaz Formation preserves abundant fish, turtles, crocodile-line reptiles and dinosaurs, including the predator Suchomimus and the giant crocodyliform Sarcosuchus. Vegetation and water were likely concentrated around channels during dry intervals. Fossils accumulated across time and space, so the formation's famous animals should not all be imagined in one permanent gathering.

Ouranosaurus could crop vegetation on four limbs and rear or move bipedally when useful. Its cheek teeth processed tough plant matter, while the deep trunk accommodated a large digestive system. The tall-spined back has inspired hypotheses involving display, temperature control, fat storage and support of a thick ridge. Bone alone cannot yet distinguish these soft-tissue models, and there is no preserved colour pattern, mating display or thermoregulatory measurement. Thumb spikes were potential defensive or foraging tools, but their exact use is not directly recorded.

• Its hand combined a thumb spike, hoof-like central fingers and a mobile fifth digit.
• The Venice skeleton helped scientists untangle which bones belonged to the original paratype.
• Its back spines extend farther along the body than the familiar shoulder sail of a bison.
• Ouranosaurus lived in the same formation as Suchomimus and Sarcosuchus.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Géologie et paléontologie du gisement de Gadoufaoua (Aptien du Niger)

   Philippe Taquet · Cahiers de Paléontologie · 1976

   Open source
2. 02
   The Venice specimen of Ouranosaurus nigeriensis (Dinosauria, Ornithopoda)

   Filippo Bertozzo, Fabio Marco Dalla Vecchia, Matteo Fabbri · PeerJ 5, e3403 · 2017

   Open source
3. 03
   Searching for dinosaurs — Ouranosaurus nigeriensis

   Natural History Museum of Venice Giancarlo Ligabue

   Open source