Description and Classification

Hypselospinus was a medium to large-sized herbivorous dinosaur. Scientists estimate it grew to be about 6 to 9 meters (20 to 30 feet) long and may have weighed around 1 to 2 metric tons (about 1.1 to 2.2 short tons). It likely moved around on its strong hind legs for faster travel, meaning it was bipedal, but it could also walk on all four limbs (quadrupedally), perhaps when feeding on low-lying vegetation. Like other iguanodontians, its hands featured a thumb spike, although it may not have been as large or prominent as the one seen in the more famous Iguanodon.

Hypselospinus belongs to the group Ornithopoda, and more specifically to Iguanodontia. Iguanodontians were a very successful and widespread group of plant-eating dinosaurs during the Jurassic and Cretaceous periods. Within Iguanodontia, Hypselospinus is classified as a styracosternan. This means it is considered more closely related to dinosaurs like Iguanodon and the later hadrosaurids (also known as duck-billed dinosaurs) than to more primitive ornithopods such as Camptosaurus. For many years, fossils now assigned to Hypselospinus were thought to belong to Iguanodon fittoni. However, detailed studies of these fossil bones revealed enough unique differences to give it a new genus name. This helped distinguish it from other iguanodontians like Barilium and Mantellisaurus that lived in the same region around the same time.

Distinguishing Features

Hypselospinus had several features that help paleontologists tell it apart from its relatives:

• It possessed very tall neural spines on the vertebrae (backbones) of its back and hip region. These spines were notably taller than those of the related dinosaur Mantellisaurus and had a different shape and proportion compared to those of Iguanodon bernissartensis.
• Compared to the heavily built Iguanodon bernissartensis, Hypselospinus had a relatively more slender and graceful body structure.
• There are specific differences in the shape and structure of its hip bones, particularly the ilium and ischium, as well as in its limb bones, when compared to other iguanodontian dinosaurs from the Wealden Group of England.

Paleoenvironment and Diet

Hypselospinus lived in what is known as the Wealden Group environment of Early Cretaceous England. This area was a vast floodplain with a complex network of rivers, freshwater lakes, and swampy regions, bordered by forests. The climate at that time was generally warm and seasonal, similar to a modern Mediterranean or subtropical climate, with distinct wet and dry seasons. This environment supported a rich variety of plant life, including abundant ferns, conifers (ancestors of modern pine trees), ginkgoes, and cycads.

As an iguanodontian, Hypselospinus was an herbivore, meaning it ate plants. Its teeth were adapted for processing tough vegetation. They were packed closely together to form a broad chewing surface, efficient for grinding down plant material. Hypselospinus likely fed on the common plants available in its habitat, such as ferns, horsetails, cycads, and the young shoots and leaves of conifers. Its ability to switch between walking on two legs and four legs would have allowed it to browse for food at different heights, reaching both low-growing plants and foliage higher up in shrubs and small trees.

Significance and Ongoing Research

The identification of Hypselospinus as a separate genus has been important for understanding the true diversity of iguanodontian dinosaurs in Early Cretaceous Europe. It shows that what was once broadly categorized under the single name Iguanodon actually included several different, though related, types of dinosaurs. Studying Hypselospinus alongside its contemporaries like Barilium and Mantellisaurus helps scientists create a more detailed and accurate picture of dinosaur evolution and the ecosystems they inhabited during this part of Earth’s history.

Current research continues to explore and refine our understanding of the evolutionary relationships between different iguanodontian dinosaurs. Paleontologists carefully study the subtle anatomical differences in their fossilized bones to construct more precise family trees. Future fossil discoveries in the Wealden Group formations and other similar-aged deposits could provide more information about the specific adaptations, behavior, and lifestyle of Hypselospinus, and how it shared its environment with other dinosaurs. The exact purpose of its tall neural spines is also an area of ongoing interest, with possibilities including display to attract mates or intimidate rivals, or to help individuals recognize members of their own species.