Description and Classification

Barilium was a large plant-eating dinosaur, reaching estimated lengths of around 8 meters (26 feet) and weighing possibly 2 to 3 metric tons. Like other iguanodontians, it had a bulky body and could walk on all four legs (quadrupedal) for grazing or slow movement, but it might have been able to run on its two hind legs (bipedal) to escape danger. Its skull featured a toothless beak at the front for snipping off plants, and rows of chewing teeth further back in the jaws to grind tough vegetation.

Barilium belongs to the group Ornithopoda, which means “bird-foot,” referring to their three-toed feet. More specifically, it is classified as an iguanodontian, a diverse group of ornithopods that thrived during the Cretaceous period. It is part of a subgroup called Styracosterna, which includes other well-known dinosaurs like Iguanodon and Mantellisaurus. The only known species is Barilium dawsoni. Understanding Barilium helps scientists learn more about the variety of dinosaurs closely related to Iguanodon that lived in ancient Europe.

Distinguishing Features

Barilium had several features that help paleontologists tell it apart from other dinosaurs, especially other iguanodontians:

• It possessed a very large and heavily built ilium (the main hip bone), which is the feature its name is based on. This suggests strong leg muscles.
• The vertebrae (backbones) in its back had moderately tall neural spines, which are bony projections extending upwards. These were taller than those of the more slender Mantellisaurus but not as extremely tall as those of Hypselospinus.
• Its forelimbs were quite stout and strong, indicating that it likely spent a good amount of time supporting its weight on all four limbs.
• Like many iguanodontians, Barilium would have had a conical thumb spike on each hand, likely used for defense or possibly for gathering food.

Paleoenvironment and Diet

Barilium lived in what is now southern England during the Valanginian age of the Early Cretaceous period. At that time, this area was part of the Wealden Group, a geological formation known for its rich dinosaur fossils. The environment was a large floodplain with winding rivers, lakes, and marshy areas. The climate was likely warm and humid, with distinct wet and dry seasons.

The landscape was covered with plants like ferns, cycads, and conifers, which would have formed the main diet of Barilium. It used its horny beak to crop these plants and its specialized teeth to chew them. Barilium shared its habitat with a variety of other dinosaurs. These included other plant-eaters like the ornithopod Hypselospinus, the small Valdosaurus, and large sauropods. Meat-eating dinosaurs, such as the fish-eating Baryonyx and the large predator Neovenator, also roamed this ancient ecosystem, along with armored dinosaurs like Polacanthus.

Significance and Ongoing Research

The study of Barilium is important for understanding the diversity of ornithopod dinosaurs in Early Cretaceous Europe. For many years, numerous iguanodontian fossils from England were simply grouped under the name Iguanodon. The re-examination of these historic collections, leading to the identification of distinct genera like Barilium and Hypselospinus, shows that the dinosaur fauna of this time and place was more varied than previously thought.

Barilium helps scientists build a more detailed picture of the Wealden ecosystem and how different herbivorous dinosaurs shared resources. Ongoing research continues to refine the relationships between Barilium and other iguanodontians. Paleontologists are always hopeful for new fossil discoveries that could provide more complete skeletons, offering further insights into its appearance, posture, and behavior. The story of Barilium also highlights how science progresses, with old discoveries being revisited and reinterpreted with new knowledge and techniques.