Spinosaurus News ~

[Ngala]

Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa Hendrickx, Mateus & Buffetaut, 2016

*This image is copyright of its original author

Fig 11. Comparison of the snout of two specimens of Spinosaurus from the ‘Continental intercalaire’ of Northwestern Africa.
A–H, Fused maxillae and premaxillae of A–B, E, G, MSNM V4047 referred to Spinosaurus aegyptiacus by Dal Sasso et al. [21] (courtesy of Simone Maganuco); and C–D, F, H, MNHM SAM 124 referred to Spinosaurus maroccanus (nomen dubium) by Taquet and Russell [93] in A, C, lateral; B, D, anterior; E, F, ventral; and G, H, dorsal views. Abbreviation: mx9, ninth maxillary alveolus; pmx6, sixth premaxillary alveolus, pmx7, seventh premaxillary alveolus. Scale = 20 cm (A, E, G), 10 cm (C, F, H), 5 cm (B), 2 cm (D).

*This image is copyright of its original author

Fig 15. Jaw mechanics in the spinosaurid Spinosaurus.
A–D, Mandibular articulation; and F, G, skull in A, C, F–G, lateral; and B, D, anterior views; when A–B, F, the mouth is closed; and C–D, G, fully open, illustrating the lateral movement (in red) of the mandibular ramus for a 45° rotation of the lower jaw (courtesy of Jaime A. Headden); E, skeletal reconstruction of Spinosaurus aegyptiacus by Ibrahim et al. [22]) in swimming position in lateral view with a human (1.8 m) as a scale (modified from Ibrahim et al. [22]). This model is based on spinosaurid cranial and postcranial remains (colored in red) from the Albian-Cenomanian of Northern Africa which possibly belong to two spinosaurine taxa (see also Evers et al. [27]); H, reconstruction of a semi-aquatic Spinosaurus in fishing position (i.e., jaws wide open) in anterolateral view (courtesy of Jason Poole). Abbreviations: an, angular; ar, articular; d, dentary; ecc, ectocondyle; enc, entocondyle; j, jugal; m, maxilla; n, nasal; p, parietal; pm, premaxilla; po, postorbital; pt, pterygoid; ptf, pterygoid flange; q, quadrate; qf, quadrate foramen; qj, quadratojugal; retp, retroarticular process of the articular; sa, surangular; sq, squamosal.

Abstract:
"Six quadrate bones, of which two almost certainly come from the Kem Kem beds (Cenomanian, Upper Cretaceous) of south-eastern Morocco, are determined to be from juvenile and adult individuals of Spinosaurinae based on phylogenetic, geometric morphometric, and phylogenetic morphometric analyses. Their morphology indicates two morphotypes evidencing the presence of two spinosaurine taxa ascribed to Spinosaurus aegyptiacus and? Sigilmassasaurus brevicollis in the Cenomanian of North Africa, casting doubt on the accuracy of some recent skeletal reconstructions which may be based on elements from several distinct species. Morphofunctional analysis of the mandibular articulation of the quadrate has shown that the jaw mechanics was peculiar in Spinosauridae. In mature spinosaurids, the posterior parts of the two mandibular rami displaced laterally when the jaw was depressed due to a lateromedially oriented intercondylar sulcus of the quadrate. Such lateral movement of the mandibular ramus was possible due to a movable mandibular symphysis in spinosaurids, allowing the pharynx to be widened. Similar jaw mechanics also occur in some pterosaurs and living pelecanids which are both adapted to capture and swallow large prey items. Spinosauridae, which were engaged, at least partially, in a piscivorous lifestyle, were able to consume large fish and may have occasionally fed on other prey such as pterosaurs and juvenile dinosaurs." Reply