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Spinosaurus redescribed as giant semiaquatic theropod

Ben Creisler

It's out...

Nizar Ibrahim, Paul C. Sereno, Cristiano Dal Sasso, Simone Maganuco,
Matteo Fabbri, David M. Martill, Samir Zouhri, Nathan Myhrvold, and
Dawid A. Iurino (2014)
Semiaquatic adaptations in a giant predatory dinosaur.
Science (advance online publication)
DOI: 10.1126/science.1258750

NOTE: Supplementary material is free.

We describe adaptations for a semiaquatic lifestyle in the dinosaur
Spinosaurus aegyptiacus. These adaptations include retraction of the
fleshy nostrils to a position near the mid-region of the skull and an
elongate neck and trunk that shift the center of body mass anterior to
the knee joint. Unlike terrestrial theropods, the pelvic girdle is
downsized, the hind limbs are short, and all of the limb bones are
solid without an open medullary cavity, for buoyancy control in water.
The short, robust femur with hypertrophied flexor attachment and the
low, flat-bottomed pedal claws are consistent with aquatic
foot-propelled locomotion. Surface striations and bone microstructure
suggest that the dorsal “sail” may have been enveloped in skin that
functioned primarily for display on land and in water.


Michael Balter (2014)
Giant dinosaur was a terror of Cretaceous waterways.
Science  345(6202): 1232
DOI: 10.1126/science.345.6202.1232

Researchers have long debated whether dinosaurs could swim, but there
has been little direct evidence for aquadinos. Some tantalizing hints
have appeared, however, in claimed "swim tracks" made by the bellies
of dinos in Utah and oxygen isotopes indicating possible aquatic
habitats in a group of dinosaurs called spinosaurs. Now, a research
team working in Morocco has found the most complete skeleton yet of a
giant carnivore called Spinosaurus, very fragmentary remains of which
were first discovered in 1912 in Egypt. The new fossils not only
confirm that Spinosaurus was bigger than Tyrannosaurus rex, but also
show that it had evolutionary adaptations—ranging from pedal-like feet
to a nostril far back on the head to high bone density like that of
hippos—clearly suited for swimming in lakes and rivers.