The Upper Cretaceous (Cenomanian) Bahariya
Formation of the Bahariya Oasis in the Egyptian
Western Desert has yielded a diverse assemblage of
non-avian dinosaurs. Crocodyliforms, however, are
less diverse, being represented to date by only three
valid taxa: the notosuchian Libycosuchus
brevirostris, the stomatosuchid neosuchian
Stomatosuchus inermis, and the aegyptosuchid
eusuchian Aegyptosuchus peyeri. Here we report
Mansoura University Vertebrate Paleontology Center
(MUVP) specimen 523, an isolated, partial right
dentary of a medium- to large-sized peirosaurid
crocodyliform from the Bahariya Formation. MUVP
523 exhibits several synapomorphies of Peirosauridae, a Gondwanan Cretaceous
mesoeucrocodylian clade that has not previously
been reported from northeastern Africa. These
synapomorphies include the wide divergence angle
(48°) of the mandibular rami, the sinusoidal dorsal
margin of the dentary comprising two distinct waves,
and the mediolaterally compressed, vertical
ventrolateral surface anterior to the mandibular
fenestra. Additionally, the anteriormost alveoli are
strongly procumbent and the dentary is concave
lateral to the 6th/7th and 8th/9th alveoli for the reception
of two enlarged maxillary teeth. The 1st, 4th, and 11th
dentary teeth are enlarged, and the dentary crowns
are conical and triangular in labial view with a gently
curved apex. Phylogenetic analysis recovers the
Bahariya form within Peirosauridae, in a clade that
also includes Miadanasuchus oblita from the
Maastrichtian of Madagascar and Barrosasuchus
neuquenianus from the Santonian of Argentina. This
clade is supported by unambiguous synapomorphies
including a dentary symphysis that is U-shaped in
ventral view and smoothly curving anteriorly, with an
elongate, anteroposteriorly shallow concavity lateral
to 5th–10th teeth on the lateral surface of dentary to
receive an enlarged premaxillary tooth. Moreover,
the three taxa lack a ‘peg’ at the posterior edge of the
mandibular symphysis. MUVP 523 therefore
represents the first unquestionable peirosaurid from
Egypt and northeastern Africa more generally. The
new specimen augments the crocodyliform
assemblage of the Bahariya Formation and, when
considered in tandem with taxa from northwestern
Africa, demonstrates the wide geographic distribution
of Peirosauridae across northern Africa during the
middle Cretaceous. |
