Description and Classification

Morelladon was a medium-sized herbivorous dinosaur, estimated to be about 6 meters (20 feet) long and weighing around 2 tonnes (2.2 short tons). Like other iguanodontians, it could walk on all fours (quadrupedal) but was likely also capable of moving on its two hind legs (bipedal) when needed, perhaps to reach higher vegetation or to run from predators. The most striking feature of Morelladon was the set of very tall spines growing on its back vertebrae, particularly over its hips. These spines would have supported a sail-like structure or a fleshy hump along its back.

Morelladon belongs to the group Ornithopoda, which means “bird-foot,” referring to their three-toed feet. More specifically, it is classified as an iguanodontian, part of the clade Styracosterna. This group includes other well-known plant-eating dinosaurs such as Iguanodon and Mantellisaurus. Styracosternans are considered more advanced iguanodontians, closely related to the duck-billed dinosaurs (hadrosaurids) but are generally viewed as being more primitive than them.

Distinguishing Features

The key feature that sets Morelladon apart from many other iguanodontians is its prominent dorsal sail or hump. This structure was:

• Formed by very tall neural spines extending upwards from its backbones (vertebrae).
• Most pronounced over the sacral region (the vertebrae connected to the pelvis). Some of these spines could reach over 40 centimeters (16 inches) in height.
• Potentially used for display to attract mates or intimidate rivals. It might also have helped regulate body temperature, similar to structures seen in other dinosaurs like Spinosaurus or the closely related iguanodontian Ouranosaurus. Another possibility is that it was used for fat storage, like a camel’s hump.

Compared to some other iguanodontians, Morelladon appears to have had a relatively lighter build for its size.

Paleoenvironment and Diet

Morelladon lived in what is now eastern Spain during the Early Cretaceous period. The environment of the Arcillas de Morella Formation at that time was likely a coastal wetland or floodplain, with rivers, lakes, and possibly estuaries near the ancient Tethys Sea. The climate was warm and humid, supporting a rich diversity of plant life. This area was home to other dinosaurs as well, including different types of sauropods (long-necked dinosaurs), theropods (meat-eating dinosaurs), and other ornithopods.

As an herbivore, Morelladon would have fed on the plants available in its habitat. Its diet likely consisted of ferns, cycads, horsetails, and early conifers. Like other iguanodontians, it would have possessed strong jaws and teeth well-suited for chewing tough plant material, although specific details of its own teeth are not fully preserved. Its ability to switch between quadrupedal and bipedal stances would have allowed it to browse on vegetation at different heights from the ground.

Significance and Ongoing Research

The discovery of Morelladon is significant because it adds to our understanding of the diversity of iguanodontian dinosaurs in Europe during the Early Cretaceous. It highlights that dinosaurs with prominent back sails or humps were not limited to one specific group or geographic region, as similar structures evolved independently in other dinosaurs like Spinosaurus (a theropod from Africa) and Ouranosaurus (another iguanodontian from Africa). The presence of this feature in Morelladon provides another interesting example of this adaptation in the dinosaur world.

Ongoing research on Morelladon aims to better understand the exact function of its unique back structure. Paleontologists are keen to find more complete fossil remains, which would provide more information about its anatomy, growth, and behavior. Further studies will also help clarify its evolutionary relationships with other iguanodontians, such as Iguanodon and Mantellisaurus, and shed more light on the dinosaur ecosystems of ancient Iberia during this period.