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.