[N] 2006 Basal Abelisaurid and Carcharodontosaurid theropods from the Elrhaz formation
Brusatte, S. & Sereno, P. (2006) Basal Abelisaurid and Carcharodontosaurid theropods from the Elrhaz formation (Aptian-Albian) of Niger. JVP 26(3) Abstracts pp.46
Carcharodontosaurids, abelisaurids, and spinosaurids constitute nearly all large-bodied theropods from Cretaceous horizons on Gondwana. The Elrhaz Formation of Niger (Aptian-Albian, ca. 112 Ma) has yielded the earliest Gondwanan spinosaurid Suchomimus tenerensis and also preserves the remains of a basal abelisaurid and carcharodontosaurid.
The abelisaurid is known from a single individual preserving the maxilla, pelvic girdle and sacrum, vertebrae, and ribs. The maxilla is textured externally, has subquadrate alveoli, and otherwise is quite similar to that of Rugops primus from Cenomanian-age horizons. The ilium, in contrast, is noticeably more primitive than that of Majungatholus atopus and closest of kin; it has a deeper preacetabular process, a shorter postacetabular process, and a more robust pubic peduncle.
The basal carcharodontosaurid is known from isolated teeth and cranial bones, including the maxilla, frontal, and postorbital. The blade-shaped teeth are smooth and do not have the marginal enamel wrinkles that characterize Carcharodontosaurus and Giganotosaurus. Compared to these genera, the maxilla is not as deep, is not textured externally by vertical grooves, and has both promaxillary and maxillary fenestrae. Compared to Acrocanthosaurus, the new taxon has a broader antorbital fossa bordering the ventral margin of the antorbital fenestra.
The prominent postorbital brow extends anteriorly to contact the lacrimal and exclude the frontal from the orbital margin, but the postorbital-lacrimal contact is not nearly as well-developed as in known carcharodontosaurids. Phylogenetic analysis places these taxa near the base of their respective clades and suggests that large-body size and many of the cranial features that characterize abelisaurids and carcharodontosaurids were already in place by the mid-Cretaceous.