Description and Classification

Fendusaurus was a herbivorous dinosaur that primarily walked on two legs (bipedal). Scientists estimate it reached lengths of around 3 to 4 meters (10 to 13 feet) and weighed between 200 and 300 kilograms (440 to 660 pounds). This made it a relatively small dinosaur compared to some of its giant contemporaries.

It belongs to the Ornithopoda group, which includes other plant-eating dinosaurs like Iguanodon and Hypsilophodon. Fendusaurus is considered an early member of the Iguanodontia, a subgroup within Ornithopoda. This means it shares some characteristics with agile, smaller ornithopods but also shows some early traits seen in later, larger iguanodontians. Its skeletal structure indicates it was a fairly agile runner, likely using its speed to evade predators. It possessed a long tail for balance and powerful hind limbs. Its forelimbs were shorter but could have been used to support its body when feeding on low-growing plants.

The skull of Fendusaurus was relatively narrow and featured a horny beak at the front, ideal for snipping off vegetation. Further back in its jaws, it had rows of cheek teeth designed for grinding tough plant material, a common adaptation for herbivorous dinosaurs.

Distinguishing Features

Fendusaurus can be identified by several key features that set it apart from other dinosaurs:

• A prominent and deep groove that ran along the midline of its snout, from just behind its nostrils to the area between its eyes. The exact purpose of this “split” is unknown, but it might have been used for display to attract mates or recognize members of its own species.
• Its hands had relatively long and somewhat flexible fingers compared to the stockier hands of later iguanodontians, suggesting it might have had some ability to grasp or manipulate food.
• A specific arrangement of teeth: the teeth at the front of its cheek rows were more leaf-shaped, while those further back were more diamond-shaped and robust for efficient grinding.
• Like many other ornithopods, Fendusaurus had ossified (bony) tendons along its spine and tail. These rod-like structures helped to stiffen the back and tail, providing support and improving balance while running.

Paleoenvironment and Diet

During the Early Cretaceous, the region of modern-day Spain where Fendusaurus lived was a warm, subtropical environment. The landscape likely included open woodlands, vast fern prairies, and river systems with lush floodplains. This provided ample food and habitat for a variety of dinosaurs.

Fendusaurus shared its world with other dinosaurs. These included giant long-necked sauropods like Turiasaurus, other ornithopods of different sizes, and meat-eating theropods such as the fish-eating Baryonyx or smaller, agile predators. Overhead, pterosaurs would have soared, and the ecosystem also included early types of crocodiles, turtles, and small mammals.

As an herbivore, Fendusaurus fed on plants. Its beak was suited for cropping low-growing vegetation such as ferns, cycads, and young conifers. Its cheek teeth then ground down these tough plants. The unique groove on its snout might have supported a colorful soft-tissue structure for display, or perhaps housed a gland, though more fossil evidence is needed to confirm its function.

Significance and Ongoing Research

The discovery of Fendusaurus is important because it adds to our understanding of the diversity and evolution of ornithopod dinosaurs in Europe during the Early Cretaceous. It helps paleontologists understand the relationships between earlier, more primitive ornithopods and the later, larger, and more specialized iguanodontians, such as the famous Iguanodon.

Current research on Fendusaurus is focused on several key questions. Scientists are eager to find more complete skeletons, especially skulls, which could provide more clues about the function of the distinctive snout groove. There is speculation that this groove might have been brightly colored for display or even supported a small crest.

Detailed studies of its limb bones and the places where muscles attached are helping to reconstruct how Fendusaurus moved and how agile it was compared to other ornithopods like Hypsilophodon. Chemical analysis of its teeth and bones (isotopic analysis) might also reveal more specific details about its diet and whether it migrated seasonally. Furthermore, ongoing phylogenetic studies aim to pinpoint its exact place in the ornithopod family tree and its evolutionary links to other plant-eating dinosaurs found in Europe and other parts of the world.