Although purported fossils of abelisaurid ceratosaurs have
been previously reported from the Upper Cretaceous
(lower Cenomanian) Bahariya Formation of the Bahariya
Oasis, Western Desert of Egypt, unambiguous material of
the clade has yet to be documented from this unit. Here
we report Mansoura University Vertebrate Paleontology
Center (MUVP) specimen 477, an isolated, wellpreserved tenth cervical vertebra of a medium-sized
abelisaurid from the Bahariya Formation of the Gebel El
Dist region of the northern Bahariya Oasis. The new
vertebra shows affinities with derived Upper Cretaceous
abelisaurids from Madagascar and South America, such
as Majungasaurus crenatissimus, Carnotaurus sastrei,
Viavenator exxoni, and the generically indeterminate
Patagonian form Museo Padre Molina (MPM) specimen
99. Widely recognized cervical vertebral synapomorphies
of Abelisauridae present in the specimen include: (1) long
axis of diapophysis forms angle of 65° to midsagittal
plane; (2) dorsal surface of neural arch clearly delimited
from lateral surface of diapophysis; (3) deep
spinoprezygapophyseal and spinopostzygapophyseal
fossae; and (4) well-developed epipophyses, comparable
to those observed in the tenth cervicals of Majungasaurus
and MPM 99 (but smaller than those of Carnotaurus and
Ekrixinatosaurus novasi). Phylogenetic analysis
following the addition of MUVP 477 to a recently
published dataset recovers the Bahariya form within
Abelisauridae, either in a polytomy of all included
abelisaurids (strict consensus tree) or, interestingly, as an
early branching member of the otherwise South American
clade Brachyrostra (50% majority rule consensus tree).
MUVP 477 therefore represents the first confirmed
abelisaurid fossil from the Bahariya Formation, rendering
it the oldest definitive record of the clade from Egypt and
northeastern Africa more generally. The new vertebra
demonstrates the wide geographic distribution of
Abelisauridae across North Africa during the middle
Cretaceous and augments the already extraordinarily
diverse large-bodied theropod record of the Bahariya
Formation, a record that also includes representatives of
Spinosauridae, Carcharodontosauridae, and
Bahariasauridae. |
