A new species of “sail-backed” dinosaur has been unearthed near Castellón, Spain. This lumbering, herbivorous beast, named Morelladon beltrani, dates back 125 million years to the beginning of the Cretaceous period, meaning that it shared its environment with several kinds of Iguanodon. The new fossilized creature has been described in the journal PLOS ONE.
Although far from complete, there were plenty of remains for the paleontologists at the Autonomous University of Madrid to analyze, which included its dorsal (back) and sacral (base of spine) vertebrae, and some of its pelvic bones. M. beltrani – 6 meters (20 feet) long and 2.5 meters (8.2 feet) tall – was eventually identified by the team as an entirely new species; even the genus Morelladon is new.
This ornithischian (bird-hipped) dinosaur had to be identified by determining which of its physical features were not shared by any other species. There were eight of these unique features, known as “autapomorphies;” most distinctively, it had very elongated and vertically-facing neural spines along the dorsal vertebrae, which the authors think represents the skeletal structures that would, in their entirety, form a large sail.
Other dinosaurs have been known to have sail-like features before, including Spinosaurus, one of the largest of all known carnivorous dinosaurs, and one that also lived during the Cretaceous period. As the biological tissue of its sail has never been preserved and fossilized, paleontologists cannot definitively say what the purpose of the sail could have been.
Image credit: The fossilized remains of the neural spines, which would have formed part of a sail. Gasulla et al./PLOS ONE
In both the case of the Spinosaurus and the new M. beltrani, the prevailing theory is that their sails were used for thermoregulation, the maintenance of body temperature. These sails could have been used in one of two ways: to take in heat by basking in sunlight, or to lose heat by using it as a radiator, leaking thermal energy away from the body while standing in the shade.
There is an ongoing debate as to whether or not dinosaurs were hot or cold-blooded animals, with some scientists arguing that they were actually “gigantotherms,” meaning that their bulkiness allowed them to maintain a relatively high internal body temperature. It isn’t clear whether the presence of a sail on M. beltrani suggests it fits into any particular category.
In addition to thermoregulation, the sails would have also looked somewhat intimidating, meaning that M. beltrani may have been able to scare off predators. The authors of the study also suggest that extra fat could have been stored in the sail, which could then be used up during periods of low food supply.
As well as being a remarkable new species of dinosaur, this find has helped the team of researchers fill in several evolutionary “gaps” within the ancient ecosystem of the Iberian Peninsula (Spain and Portugal). By comparing its features that are shared with other dinosaurs (synapomorphies), the team determined that it is most closely related to Mantellisaurus atherfieldensis, a type of iguanodon.
This find adds to the mounting evidence that the Iberian Peninsula during the Cretaceous was filled with an incredibly diverse range of dinosaurs, particularly iguanodons and their close relatives.
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