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Sigilmassasaurus

Russell, 1996 /siːdʒɪlˌmɑːsəˈsɔːrəs/ Disputed

From 'Sigilmassa', the ancient city and former capital of the Tafilalt that was a center of Saharan commerce, and Greek 'sauros' ('lizard'); meaning 'Sigilmassa lizard'.

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

Sigilmassasaurus is a controversial genus of spinosaurid dinosaur that lived approximately 100 to 94 million years ago during the Late Cretaceous Period in what is now northern Africa. Named in 1996 by Canadian paleontologist Dale Russell, it contains a single species, Sigilmassasaurus brevicollis. The identity of the genus has been debated by scientists, with some considering its fossils to represent material from the closely related species Spinosaurus aegyptiacus, while others have classified it as a separate taxon, forming the clade Spinosaurini with Spinosaurus as its sister taxon.

Under dispute

The validity of Sigilmassasaurus is actively contested, and the genus is known only from isolated vertebrae that were never found in association. Russell (1996) erected it on a single vertebra identified as a mid-cervical. Evers and colleagues (2015) reappraised the material, reinterpreted the holotype as a first dorsal, gave the genus an emended diagnosis, and rejected its referral to Spinosaurus aegyptiacus; Chiarenza and Cau (2016) concurred, and Arden and colleagues (2019) recovered it as the sister taxon of Spinosaurus in a clade Spinosaurini. Against this, Ibrahim and colleagues (2020) rebutted the emended diagnosis, reporting the ventral platform character in Spinosaurus aegyptiacus as well, and Smyth and colleagues (2020) rejected every proposed autapomorphy in turn, attributing the variation to axial position and ontogeny within a single taxon and treating the genus as a junior synonym of Spinosaurus aegyptiacus. Rauhut and colleagues (2025) tested that single-taxon hypothesis in a sensitivity analysis. No consensus has emerged, so the species is marked disputed and the genus retained at Spinosaurinae. Which taxon the vertebrae of Spinosaurus maroccanus belong to is contested on the same evidence: Evers and colleagues (2015) refer them to Sigilmassasaurus brevicollis as a different axial position of one animal, whereas Ibrahim and colleagues (2020) reject that referral and keep the name with Spinosaurus aegyptiacus. The name is therefore carried as a possible synonym of both species, asserting neither destination.

Diagnosis

  1. Neural spines of cervical vertebrae short, wider transversely than anteroposteriorly long
  2. Intercentral articulations of cervical vertebrae wider than high, exceeding centrum length in width
  3. Cervical series strongly arched into a U-shaped curve in lateral aspect
  4. Parapophyses project ventrolaterally beyond the rim of the intercentral articulations
  5. Hypapophyses most powerfully developed at the mid-cervical region, diminishing toward the cervico-dorsal transition
  6. Posterior cervical centrum broad, with posterior width to length ratio of about 1.46, a small pleurocoel, and a greatly enlarged hypapophyseal peduncle
  7. Mid-cervical vertebrae with an offset, transversely convex, strongly rugose triangular platform at the posterior end of the ventral side, confluent with a ventral keel anteriorly
  8. Anteriorly broad centroprezygapophyseal lamina with no or strongly reduced centroprezygapophyseal fossa already present in anterior mid-cervical vertebrae
  9. Reduced neural arch lamination with no or incomplete distinction between anterior and posterior centrodiapophyseal laminae in posterior cervical and first dorsal vertebrae
  10. Small elongate fossa on either side of the base of the neural spine in the last cervical and first dorsal vertebrae

Species

Sigilmassasaurus brevicollis Russell, 1996 Disputed

Type species

From Latin 'brevis' ('short') and 'collum' ('neck'), alluding to the shortness of the cervical centra.

Holotype
CMN 41857 , Canadian Museum of Nature
Material
Single isolated vertebra with a fairly complete neural arch, lacking part of the right transverse process and the tip of the neural spine.
Horizon
Kem Kem Group, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Taouz, Draa-Tafilalet, Morocco

Synonyms

  • Spinosaurus maroccanus possible subjective

    Erected by Russell (1996) in the same paper as Sigilmassasaurus brevicollis, on CMN 50791, an isolated mid-cervical vertebra. Evers and colleagues (2015) found a morphological continuum between the two holotypes, listed CMN 50791 among the referred material of Sigilmassasaurus as a mid-cervical of the same animal, and kept brevicollis as the species epithet because neither name has page priority. Ibrahim and colleagues (2020) reject that referral and retain the name under Spinosaurus aegyptiacus, so the destination of the name is contested.

References

  1. 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.

    Erects the genus and species on an isolated vertebra from the Tafilalt, identified as a posterior cervical.

    russell1996b
  2. 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

    Reappraises the material, reinterprets the holotype as a first dorsal, emends the diagnosis, rejects referral to Spinosaurus aegyptiacus, and gives the type horizon as Ifezouane or Aoufous.

    evers2015a
  3. 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

    Rejects every proposed autapomorphy and treats the genus as a junior synonym of Spinosaurus aegyptiacus.

    smyth2020a
  4. 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

    Rebuts the emended diagnosis, reporting the ventral platform character in Spinosaurus aegyptiacus, and rejects the referral of Spinosaurus maroccanus.

    ibrahim2020a
  5. Arden, T. M. S.; Klein, C. G.; Zouhri, S.; Longrich, N. R. (2019). Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in spinosaurids. Cretaceous Research 93: 275-284. Elsevier. doi:10.1016/j.cretres.2018.06.013

    Recovers the genus as the sister taxon of Spinosaurus in a clade Spinosaurini.

    arden2019a
  6. Chiarenza, A. A.; Cau, A. (2016). A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa. PeerJ 4: e1754. PeerJ. doi:10.7717/peerj.1754

    Concurs that the genus is a distinct spinosaurid rather than referable to Spinosaurus aegyptiacus.

    chiarenza2016a
  7. Rauhut, O. W. M.; Canudo, J. I.; Castanera, D. (2025). Revision of the theropod dinosaur Camarillasaurus cirugedae from the Early Cretaceous (Barremian) of Teruel province, Spain. Palaeontologia Electronica 28(3): 1-67. doi:10.26879/1543

    Tests the single-taxon hypothesis for the Kem Kem spinosaurid material in a sensitivity analysis.

    rauhut2025a
  8. Kellermann, M.; Cuesta, E.; Rauhut, O. W. M. (2025). Re-evaluation of the Bahariya Formation carcharodontosaurid (Dinosauria: Theropoda) and its implications for allosauroid phylogeny. PLOS ONE 20(1): e0311096. Public Library of Science (PLoS). doi:10.1371/journal.pone.0311096

    Notes the claimed shared occurrence of the genus in the Bahariya Formation and the Kem Kem Group as warranting reexamination.

    kellermann2025a