Open Paleo

Spinosaurus

Stromer, 1915 SPIEN-o-SAWR-us /ˌspaɪnəˈsɔːrəs/

From Latin spina (spine, thorn) and Greek sauros (lizard); meaning "spine lizard", named for the conspicuously tall neural spines of the trunk vertebrae that supported a dorsal sail.

100.5–93.9 million years ago Cenomanian, Late Cretaceous
Late Cretaceous stages

Spinosaurus is the type genus of Spinosauridae and one of the most distinctive Cretaceous theropods, recognized for the enormously tall neural spines of its dorsal vertebrae that supported a dorsal sail or hump. The genus was erected by Ernst Stromer in 1915 on a partial skeleton recovered in 1912 by Stromer's collector Richard Markgraf from the Bahariya beds of the Western Desert of Egypt (specimen BSP 1912 VIII 19 in the Bayerische Staatssammlung in Munich). The original type material — including the iconic mandibles and elongate-spined dorsals — was destroyed in the British bombing of Munich in April 1944, leaving only Stromer's plates and descriptions. Stromer (1934) added more material, including a smaller specimen treated informally as "Spinosaurus B" (later partly the basis of Russell's 1996 S. maroccanus). Ibrahim and colleagues (2014) designated FSAC-KK 11888, a partial skeleton from the Kem Kem beds of southeastern Morocco, as the neotype of S. aegyptiacus, and proposed on the basis of pachyostotic limb bones, retracted nostrils, and reduced hindlimbs that Spinosaurus was a semi-aquatic predator capable of obligate quadrupedal locomotion on land. Subsequent work (notably Ibrahim and colleagues 2020 on the paddle-tail and Sereno and colleagues 2022 in response) has continued to debate the degree of aquatic adaptation, but the broad picture of a piscivorous, river-dwelling spinosaurid with reduced hindlimbs and dense limb bones is now widely accepted.

Diagnosis

  1. Dentary rami long and low-set in the middle, bearing about 15 awl-shaped teeth per ramus, with strongly heterodont positions (large 2nd-4th, small 5th-10th, larger 11th-14th).
  2. Teeth straight to gently curved, sub-circular in cross-section, with smooth (non-serrated) anterior and posterior keels.
  3. Fleshy nostril retracted to a posteriorly placed narial fossa on the skull, far from the snout tip.
  4. Free dorsal vertebral centra elongate, hourglass-shaped in dorsal view, and strongly opisthocoelous, lacking a ventral keel.
  5. Neural spines of dorsal vertebrae extraordinarily tall (up to ~8x centrum height), laterally compressed, broadened ventrally and dorsally, supporting a dorsal sail.
  6. Anterior dorsal centra exceptionally broad and concavoconvex, creating a horizontal cervicodorsal hinge.
  7. Long bones (femur, tibia, manual phalanges) with solid shafts lacking an open medullary cavity; bone density 30-40% greater than in other large theropods (pachyostosis).
  8. Femur substantially shorter than tibia and hindlimb length only ~19% of body length; iliac blade reduced to roughly half the surface area of other comparably sized theropods.

Species (2)

Spinosaurus aegyptiacus Stromer, 1915

Type species

From Latin aegyptiacus, "of Egypt", after the country where Stromer's original type material was found at Bahariya.

Neotype
FSAC-KK 11888 , Département of Géologie (Paléontologie), Faculté des Sciences Aïn Chock, Université Hassan II
Material
Partial skeleton including portions of the skull, cervical, dorsal, sacral and caudal vertebrae, ilium, manual phalanges, femur, tibia and pedal elements; subadult.
Notes
Designated as neotype by Ibrahim and colleagues (2014) after the destruction of Stromer's original holotype (BSP 1912 VIII 19, Munich) in 1944. The designation is contested; Evers and colleagues (2015) argued it does not meet ICZN Article 75 requirements (unverified commercial provenance, a Kem Kem locality far from Stromer's Bahariya type locality, and possible multiple Kem Kem spinosaurid taxa). The ICZN has not ruled, and FSAC-KK 11888 remains in widespread use as the de facto neotype.
Horizon
lower Douira Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Zrigat, Errachidia, Morocco Ibrahim and colleagues (2014), designating the neotype, place it "at the base of the upper unit of the Kem Kem beds", 18 km northeast of Erfoud, and Ibrahim and colleagues (2020) confirm "its origin in the Douira Formation" at Zrigat, with the section measured at the nearby Al Gualb Mesa. Smyth and colleagues (2020), citing the 2014 paper, give "Towards top of Ifezouane Formation", the lower unit. The coordinate is theirs; neither Ibrahim paper prints one.

Synonyms

  • Spinosaurus maroccanus possible subjective

    Erected by Russell (1996) on CMN 50791, an isolated mid-cervical vertebra from the Kem Kem Group diagnosed on centrum proportions alone. Ibrahim and colleagues (2014) synonymized it with Spinosaurus aegyptiacus; Ibrahim and colleagues (2020) reaffirmed that reading on the mid-cervical of the FSAC-KK 11888 neotype, which matches CMN 50791 in proportions and carries the same rugose ventral platform, and Smyth and colleagues (2020) concurred. Evers and colleagues (2015) instead refer CMN 50791 to Sigilmassasaurus brevicollis, so the destination of the name is contested.

Spinosaurus mirabilis Sereno et al., 2026

From Latin 'mirabilis' meaning 'astonishing', in reference to the hypertrophied scimitar-shaped nasal-prefrontal crest of the holotype.

Holotype
MNBH JEN1 , Musée National Boubou Hama
Material
Associated right premaxilla, both maxillae, base and bottom half of the fused nasal crest with portions of both prefrontals, alveolar edge of the right dentary, and five maxillary teeth.
Horizon
Farak Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Sirig Taghat, Jenguebi area, Agadez, Niger
Diagnosis
  1. Low snout with parallel dorsal and ventral margins in lateral profile.
  2. Greater spacing of posterior maxillary and opposing dentary teeth.
  3. Scimitar-shaped nasal-prefrontal crest arching upward and backward with a lateral eminence offset toward the anterior margin; the crest is proportionally taller, exceeding cranium height at the orbits (lower and more fluted in S. aegyptiacus).
  4. Postaxial cervical pleurocoels with greater anteroposterior diameter than adjacent parapophyseal articular facets.
  5. Tibial articular depression for the ascending process of the astragalus reduced in area, with the medial malleolus edge exposed in anterior view.

References

  1. Stromer, E. (1915). Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec. [Results of Prof. E. Stromer's research expeditions in the deserts of Egypt. II. Vertebrate remains of the Baharije Stage (lowermost Cenomanian). 3. The original of the theropod Spinosaurus aegyptiacus nov. gen., nov. spec.]. Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse 28(3): 1-32.

    Erects the genus and family Spinosauridae on a partial skeleton recovered in 1912 by Markgraf from Bahariya, Egypt. Holotype later destroyed in the 1944 Munich bombing.

    stromer1915a
  2. Stromer, E. (1934). Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 13. Dinosauria [Results of the expeditions of Professor E. Stromer in the Egyptian deserts. II. Vertebrate animal remains from the Baharîje bed (lowest Cenomanian). 13. Dinosauria]. Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge 22: 1-79.

    Follow-up monograph adding specimen 1922 X 45 and corrections to the 1915 description; informally separates a smaller "Spinosaurus B" without erecting a binomial.

    stromer1934a
  3. Ibrahim, N.; Sereno, P. C.; Dal Sasso, C.; Maganuco, S.; Fabbri, M.; Martill, D. M.; Zouhri, S.; Myhrvold, N.; Iurino, D. A. (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science 345(6204): 1613-1616. doi:10.1126/science.1258750

    Designates FSAC-KK 11888 (Kem Kem beds, Morocco) as the neotype of Spinosaurus aegyptiacus and argues for semi-aquatic, facultatively quadrupedal habits and pachyostotic limb bones.

    ibrahim2014a
  4. Evers, S. W.; Rauhut, O. W. M.; Milner, A. C.; McFeeters, B.; Allain, R. (2015). A reappraisal of the morphology and systematic position of the theropod dinosaur Sigilmassasaurus from the "middle" Cretaceous of Morocco. PeerJ 3: e1323. PeerJ. doi:10.7717/peerj.1323

    Challenges the FSAC-KK 11888 neotype designation as not meeting ICZN Article 75 (uncertain provenance, Kem Kem vs Bahariya locality mismatch, possible multiple Kem Kem spinosaurids).

    evers2015a
  5. Sereno, P. C.; Vidal, D.; Myhrvold, N. P.; Johnson-Ransom, E.; Ciudad Real, M.; Baumgart, S. L.; Sánchez Fontela, N.; Green, T. L.; Saitta, E. T.; Adamou, B.; Bop, L. L.; Keillor, T. M.; Fitzgerald, E. C.; Dutheil, D. B.; Laroche, R. A. S.; Demers-Potvin, A. V.; Simarro, Á.; Gascó-Lluna, F.; Lázaro, A.; Gamonal, A.; Beightol, C. V.; Reneleau, V.; Vautrin, R.; Bertozzo, F.; Granados, A.; Kinney-Broderick, G.; Mallon, J. C.; Lindoso, R. M.; Ramezani, J. (2026). Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation. Science 391: eadx5486. doi:10.1126/science.adx5486

    Erects Spinosaurus mirabilis from the Cenomanian Farak Formation of Niger on the basis of MNBH JEN1, a subadult cranium with a hypertrophied scimitar-shaped nasal-prefrontal crest.

    sereno2026a
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  7. Ibrahim, N.; Sereno, P. C.; Varricchio, D. J.; Martill, D. M.; Dutheil, D. B.; Unwin, D. M.; Baidder, L.; Larsson, H. C. E.; Zouhri, S.; Kaoukaya, A. (2020). Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco. ZooKeys 928: 1-216. doi:10.3897/zookeys.928.47517

    Describes Spinosaurus tail material bearing on its aquatic locomotion, and rejects the referral of the Spinosaurus maroccanus holotype to Sigilmassasaurus brevicollis.

    ibrahim2020a
  8. Smyth, R. S. H.; Ibrahim, N.; Martill, D. M. (2020). Sigilmassasaurus is Spinosaurus: a reappraisal of African spinosaurines. Cretaceous Research 114: 104520. Elsevier BV. doi:10.1016/j.cretres.2020.104520

    Treats Spinosaurus maroccanus and Sigilmassasaurus brevicollis as junior synonyms of Spinosaurus aegyptiacus, attributing their proposed autapomorphies to axial position and intraspecific variation.

    smyth2020a
  9. Russell, D. A. (1996). Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco. Bulletin du Muséum national d'Histoire naturelle, série 4, section C 18(2-3): 349-402. Muséum national d'Histoire naturelle. russell1996b