Upper Cretaceous deposits exposed in southern Egypt, near
the Dakhla Oasis in the Western Desert, preserve abundant
vertebrate fossils from nearshore marine paleoenvironments.
Fieldwork carried out by researchers from the Mansoura
University Vertebrate Paleontology Center in this area during
2008, 2010, 2011, and 2013 resulted in the discovery of
numerous new vertebrate fossil localities within the upper
Campanian part of the Duwi Formation. Fossils recovered
from this unit include those of sharks, sawfishs,
actinopterygians, and marine reptiles (mosasaurs and
plesiosaurs).
Here we report on elasmosaurid (Sauropterygia: Plesiosauria:
Elasmosauridae) and mosasaurid (Squamata: Mosasauridae)
fossils from the Duwi Formation. Elasmosaurids are
represented by numerous large posterior cervical and dorsal
vertebrae that are referable to this plesiosaur clade based on
their possession of centra with lateral ridges and dumbbellshaped articular facets. Mosasaurids are the most abundant
and diverse marine reptiles recovered from the Duwi
Formation, with many craniodental (e.g., dentaries and teeth
with differing morphologies) remains and dozens of vertebrae
having been identified as those of Mosasaurinae or
Halisaurinae. Within Mosasaurinae, an isolated, robust, and
globular tooth crown of Globidens and a complete tooth of
Carinodens (identified on the basis of its lateral flattening and
two relatively pronounced sulci) indicate the presence of
Globidensini. Many fragmentary dentaries pertain to an
indeterminate mosasaurine, with two of these preserving teeth
in situ and another showing a replacement tooth developed
within a resorption pit. One small, fragmentary dentary with
two preserved teeth is referred to Halisaurinae based on the
presence of small, striated, hooked, snake-like teeth. This
fossil represents the first record of Halisaurinae from Egypt
and the oldest occurrence of this group from northern Africa.
Egyptian mosasaurids ranged in size from small-bodied (~3 to
4 m) Halisaurinae to medium-sized (~6 to 8 m) Mosasaurinae,
and were similarly diverse in morphology. Tooth crowns
range in shape from cones adapted to pierce and hold, to
bulbous teeth adapted to crush, to cutting blades; jaw
morphology is also diverse. The new elasmosaurid and
mosasaurid remains from the Duwi Formation therefore reveal
high taxonomic and functional diversity and elevated
endemism in the uppermost Cretaceous marine reptile faunas
of northeastern Africa. |
