Abstract
We describe the partially preserved femur of a large-bodied theropod dinosaur from the Cenomanian “Kem Kem Compound Assemblage” (KKCA) of Morocco. The fossil is housed in the Museo Geologico e Paleontologico “Gaetano Giorgio Gemmellaro” in Palermo (Italy). The specimen is compared with the theropod fossil record from the KKCA and coeval assemblages from North Africa. The combination of a distally reclined head, a not prominent trochanteric shelf, distally placed lesser trochanter of stout, alariform shape, a stocky shaft with the fourth trochanter placed proximally, and rugose muscular insertion areas in the specimen distinguishes it from Carcharodontosaurus, Deltadromeus and Spinosaurus and supports referral to an abelisaurid. The estimated body size for the individual from which this femur was derived is comparable to Carnotaurus and Ekrixinatosaurus (up to 9 meters in length and 2 tons in body mass). This find confirms that abelisaurids had reached their largest body size in the “middle Cretaceous,” and that large abelisaurids coexisted with other giant theropods in Africa. We review the taxonomic status of the theropods from the Cenomanian of North Africa, and provisionally restrict the Linnean binomina Carcharodontosaurus iguidensis and Spinosaurus aegyptiacus to the type specimens. Based on comparisons among the theropod records from the Aptian-Cenomanian of South America and Africa, a partial explanation for the so-called “Stromer’s riddle” (namely, the coexistence of many large predatory dinosaurs in the “middle Cretaceous” record from North Africa) is offered in term of taphonomic artifacts among lineage records that were ecologically and environmentally non-overlapping. Although morphofunctional and stratigraphic evidence supports an ecological segregation between spinosaurids and the other lineages, the co-occurrence of abelisaurids and carcharodontosaurids, two groups showing several craniodental convergences that suggest direct resource competition, remains to be explained.
Highlights
The dinosaurs from the Aptian-Cenomanian of North Africa are mainly known from a few articulated skeletons and several isolated bones, the majority of which areHow to cite this article Chiarenza and Cau (2016), A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa
The fossil comes from the region of Taouz (Errachidia Province, Morocco, near the Moroccan-Algerian border) and was donated in 2005 to the Museo Geologico e Paleontologico “Gaetano Giorgio Gemmellaro” in Palermo (Italy) by a donor who had purchased it from a Moroccan fossil dealer
Since referral of isolated and non-overlapping specimens to the same taxon is a hypothesis itself, we briefly review here the taxonomic status of the known theropod taxa from the Kem Kem Compound Assemblage (KKCA) and–where relevant to the discussion–from penecontemporaneous assemblages from North Africa (Fig. 2)
Summary
The dinosaurs from the Aptian-Cenomanian of North Africa are mainly known from a few articulated skeletons and several isolated bones, the majority of which areHow to cite this article Chiarenza and Cau (2016), A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa. The specimen differs from all other known theropod frontals from the “mid-Cretaceous” of North Africa, in particular Carcharodontosaurus saharicus and the braincase referred to C. iguidensis (Sereno et al, 1996; Brusatte & Sereno, 2007; Sereno & Brusatte, 2008), and shares a set of unique features with the frontals from the Aptian of Niger referred to the basal carcharodontosaurid Eocarcharia dinops (Brusatte & Sereno, 2008).
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