in modern birds and crocodilians. This has also been proposed for the related genus Irritator, on account of the prominent sagittal crest running towards the back of its head. However, Evers and colleagues noted that a more thorough biomechanical analysis is required for confirmation of this condition in Sigilmassasaurus. Several large theropods (more than one tonne) are known from the Cenomanian of northern Africa, raising questions about how such animals would have coexisted. Species of Spinosaurus, the longest known theropod, have been found in both Morocco and Egypt, as has the huge Carcharodontosaurus. Two smaller theropods, Deltadromeus and Bahariasaurus, have also been found in Morocco and Egypt, respectively, and may be closely related or possibly the same genus. Sigilmassasaurus, from Morocco, and "Spinosaurus B", from Egypt, represent a fourth type of large predator. This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over one tonne in weight, as well as several smaller genera. Differences in head shape and body size among the large North African theropods may have been enough to allow niche partitioning as seen among the many different predator species found today in the African savanna. See also Spinosauridae References Spinosaurids Late Cretaceous dinosaurs of Africa Cenomanian life Cretaceous Morocco Fossils of Morocco Fossil taxa described in 1996 Taxa named by Dale Russell