Description and Classification

Portellsaurus was a medium-sized herbivorous dinosaur. Scientists estimate it likely reached lengths of around 6 to 8 meters (about 20 to 26 feet) and weighed several tons. Like other related ornithopods, it probably walked on its two hind legs most of the time. However, it could also move on all fours, especially when feeding on low-lying plants. As an ornithopod, it belonged to a large group of plant-eating dinosaurs that included well-known genera like Iguanodon and the later “duck-billed” hadrosaurs.

Portellsaurus is classified within the Styracosterna, a group of advanced iguanodontian ornithopods. It is considered to be more closely related to hadrosauroids (the group that includes true hadrosaurs, or “duck-billed dinosaurs”) than to dinosaurs like Iguanodon. However, Portellsaurus is not a hadrosaurid itself. This places it in an interesting position in the evolutionary tree of these dinosaurs. It shows some features that were leading towards the later, more specialized duck-billed dinosaurs that became very common in the Late Cretaceous period.

Distinguishing Features

Since Portellsaurus is currently known only from a partial lower jaw bone (the right dentary), its unique features are identified from this specific fossil. These features help paleontologists tell it apart from other similar dinosaurs:

• It has a distinctive deep, oval-shaped pit or cavity on the outer side of the jawbone. This pit is located just below where a large bony projection called the coronoid process begins. This unique cavity is a key identifying feature of Portellsaurus.
• The jawbone lacks a noticeable outward curve or inset (called a buccal emargination) along the tooth row near the front of the jaw, where there is a toothless gap (diastema). The specific shape of this area is different from that of many other related ornithopod dinosaurs.

These features, especially the unique cavity on the jawbone, are important for confirming that Portellsaurus is a distinct genus of dinosaur.

Paleoenvironment and Diet

Portellsaurus lived in what is now eastern Spain. During the Early Cretaceous, this region was a coastal environment with river systems and deltas. The fossils of Portellsaurus were found in the Margas de Mirambell Formation, which preserves rocks and fossils from this ancient landscape, indicating it was rich in vegetation. This area would have supported a diverse community of dinosaurs. Other dinosaurs found in the same general region and from a similar time period include sauropods (large, long-necked plant-eaters), other ornithopods like Morelladon and relatives of Iguanodon, and various theropod (meat-eating) dinosaurs.

As an ornithopod dinosaur, Portellsaurus was an herbivore, meaning it ate plants. Its teeth, though not fully known beyond what the jawbone suggests, would have been adapted for grinding tough plant material. It likely fed on plants common during the Early Cretaceous, such as ferns, cycads, and conifers. Early types of flowering plants were also beginning to appear during this time and might have been part of its diet. The structure of its jaw suggests it could efficiently process vegetation to get the nutrients it needed to survive.

Significance and Ongoing Research

The discovery of Portellsaurus is significant because it adds to our understanding of the diversity and evolution of iguanodontian dinosaurs in Europe during the Early Cretaceous period. The Iberian Peninsula (modern-day Spain and Portugal) has become an important area for finding fossils from this period, and Portellsaurus helps fill in gaps in the fossil record. It provides more clues about the evolutionary steps that led from earlier iguanodontians to the very successful hadrosauroid dinosaurs.

Ongoing research related to Portellsaurus primarily involves hoping for the discovery of more fossil material. Finding additional bones, such as parts of the skull, limbs, or vertebrae, would allow scientists to learn much more about its overall anatomy, its exact size, and how it lived. Further analysis of its known jawbone continues to help scientists refine its exact place in the ornithopod family tree and understand the relationships between different European iguanodontians like Mantellisaurus or Proa, and other styracosternan dinosaurs found around the world.