Recent discoveries have begun to elucidate the affinities of
the Upper Cretaceous nonmarine vertebrate faunas of
continental Africa, reinvigorating exploration into this
critical gap in understanding of Mesozoic
paleobiogeography and evolutionary history. For example,
titanosaurian sauropod dinosaurs from Egypt
(Mansourasaurus from the Campanian Quseir Formation)
and Tanzania (Rukwatitan and Shingopana from the
Namba Member of the Galula Formation) offer nascent
support for the hypothesis that Late Cretaceous faunas
from northern Africa had closer relationships to those from
Eurasia than to those from southern Africa or other
Gondwanan regions. Here we present an associated postcranial skeleton of a
medium-sized titanosaur from the Quseir Formation of the
Kharga Oasis, Egyptian Western Desert (MB.R.Vb-621–
640). Discovered in 1977, the specimen has been
repeatedly mentioned in the literature but has never been
the subject of a formally published description. The
skeleton consists of five somphospondylous dorsal
vertebrae and 12 girdle and limb elements; unfortunately,
however, it has undergone considerable taphonomic
distortion, rendering many bones incomplete and/or
compressed and leaving many anatomical interpretations
wanting. Furthermore, the comparatively well-preserved
left tibia mentioned in previous reports is currently
missing.
Preliminary phylogenetic analysis of MB.R.Vb-621–640
using tip-dating Bayesian methods suggests close affinities
with Mansourasaurus and Late Cretaceous Eurasian
titanosaurians. Support for this placement includes the
absence of a postzygodiapophyseal lamina in middle and
posterior dorsal vertebrae. Although MB.R.Vb-621–640
has only limited skeletal overlap with other Quseir
Formation titanosaur specimens, it differs from
Mansourasaurus in having a fully enclosed coracoid
foramen, proportionally more gracile limbs, and a
mediodistal groove on metatarsal I, the latter of which may
be autapomorphic. MB.R.Vb-621–640 also differs from
another, more recently collected titanosaur skeleton from
the Kharga Oasis in having a proportionally slenderer tibia,
but resembles this specimen in that the posterior dorsals of
the latter also lack a postzygodiapophyseal lamina,
suggesting that it too may have affinity with European and
Asian taxa. As such, the growing collection of
titanosaurian fossils from the Campanian of Egypt supports
hypotheses of connectivity between northern African and
Eurasian dinosaur faunas during the Late Cretaceous. |
