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 These creatures stood out from the others in this Cretaceous
Period landscape by virtue of the unusual sail-like structure on
their backs, and experts today can only hypothesize about its
function.
Scientists announced on Wednesday the discovery near the town of
Morella in Spain's Castellón Province of the fossil remains of a
medium-sized dinosaur they named Morelladon, a four-legged herbivore
that measured 6 meters (20 feet) long.
Protruding from its back was a series of bony spines that formed the
sail-like structure that stood about 2 feet (60 cm) tall.
"The sail could help in heat exchange - thermoregulation - focused
on releasing excess body heat into the environment, like the ears of
the modern-day elephants, or as a storage place for fat to be used
during periods of low food supply," said paleontologist Fernando
Escaso of the National University of Distance Education's
Evolutionary Biology Group in Spain.
 The structure also could have served a display role in attracting
mates, Escaso added.
Escaso noted that sail-like structures appeared periodically in the
evolutionary history of vertebrates, often in animal groups not
closely related to one another.
Another plant-eating dinosaur called Ouranosaurus with similarities
to Morelladon lived about the same time in Africa. The biggest
sail-backed creature was Spinosaurus, which lived a semi-aquatic
lifestyle 95 million years ago in Africa. At 50 feet long (15
metres) and 7 tons, it was the biggest dinosaur predator on record,
larger even than Tyrannosaurus rex.
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Millions of years before the rise of the dinosaurs, there were other
sail-backed creatures including the carnivorous reptile
Arizonasaurus, the amphibian Platyhystrix and the distant mammal
relatives Dimetrodon and Edaphosaurus.
Morelladon is known from a partial skeleton including the spines,
other vertebrae, pelvic bones, a thigh bone and teeth.
Northeastern Spain during Morelladon's time alternated between wet
and dry periods, with strong temperature variations ranging from 40
degrees Fahrenheit (4 Celsius) to about 104 F (40 C).
Escaso said the main predator in the area was Baryonyx, a relative
of Spinosaurus, and there were other plant-eating dinosaurs around
as well as crocodilians and the flying reptiles called pterosaurs.
The research was published in the journal PLOS ONE.
(Reporting by Will Dunham; Editing by Peter Cooney)
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