Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 6, e4785

The Smallest Biggest Theropod Dinosaur: A Tiny Pedal Ungual of a Juvenile Spinosaurus From the Cretaceous of Morocco


The Smallest Biggest Theropod Dinosaur: A Tiny Pedal Ungual of a Juvenile Spinosaurus From the Cretaceous of Morocco

Simone Maganuco et al. PeerJ.


We describe a nearly complete pedal ungual phalanx, discovered in the Kem Kem Beds (Cenomanian) of Tafilalt region, south-eastern Morocco. The bone is symmetric, pointed, low, elongate, and almost flat ventrally in lateral aspect. This peculiar morphology allows to refer the specimen to the smallest known individual of the genus Spinosaurus. The bone belongs to an early juvenile individual and it is proportionally identical to the ungual of the third digit of a large partial skeleton recently found, suggesting an isometric growth for this part of the pes and the retention of peculiar locomotor adaptations-such as traversing soft substrates or paddling-during the entire lifespan.

Keywords: Cenomanian; Morocco; Pedal ungual; Spinosaurus; Theropoda.

Conflict of interest statement

The authors declare that they have no competing interests.


Figure 1
Figure 1. Geographic map of the fossil location, Morocco.
Geographic map of the fossil location South of Erfoud, between the villages of Taouz and Begaa, Errachidia Province, Morocco; the main localities and landscape elements cited in the text are shown in the map. The asterisk marks the site from where the specimen MSNM V6894 was collected (modified from Ibrahim et al., 2016).
Figure 2
Figure 2. Pedal ungual phalanx of Spinosaurus.
Specimen MSNM V6894 in right lateral (A), left lateral (B), dorsal (C), plantar (D), proximal (E), and distal (F) views. Abbreviations: as, articular surface; co, cortex; et, extensor tubercle; sb, spongy bone; vf, vascular furrow. Scale bar equals 5 mm. Photos by M. Zilioli, used with his permission.
Figure 3
Figure 3. Anatomical and size comparisons.
Specimen MSNM V6894 in dorsal view, compared to a cast of the right ungual III-4 of specimen FSAC-KK18888 (A). Size-comparison of selected Spinosaurus individuals from the Kem Kem Beds: MSNM V6894 (B, this paper), the neotype FSAC-KK18888 (C) and the largest known individual MSNM V4047 (D), compared with Homo (1.75 m tall). Drawing by Marco Auditore and Prehistoric Minds, used with their permission. Scale bar equals 20 mm in A. Photos by M. Zilioli and C. Dal Sasso, used with their permission.

Similar articles

See all similar articles

Cited by 1 article


    1. Alessandrello A, Bracchi G. Eldonia berbera n. sp., a new species of the enigmatic genus Eldonia Walcott, 1911 from the Rawtheyan (Upper Ordovician) of Anti-Atlas (Erfoud, Tafilalt, Morocco) Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano. 2003;144(II):337–358.
    1. Brusatte SL, Sereno PC. A new species of Carcharodontosaurus (Dinosauria: Theropoda) from the Cenomanian of Niger and a revision of the genus. Journal of Vertebrate Paleontology. 2007;27(4):902–916. doi: 10.1671/0272-4634(2007)27[902:ANSOCD]2.0.CO;2. - DOI
    1. Chiarenza AA, Cau C. A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa. PeerJ. 2016;4:e1754 doi: 10.7717/peerj.1754. - DOI - PMC - PubMed
    1. Christiansen P. Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential. Gaia. 1998;15:241–255.
    1. Currie PJ. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) form the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences. 2003;40:651–665.

Grant support

The authors received no funding for this work.

LinkOut - more resources