New Species Of Duck-Billed Dinosaur Has Odd Lower Jaw

Paleontologists have discovered a new duck-billed dinosaur in Texas. Remains of the prehistoric creature named Aquilarhinus palimentus hasms been discovered in Big Bend National Park, Texas in the 1980s, but research on the specimen hit a snag because some of its badly-weathered bones were stuck together making them difficult to study.

In the 1990s, researchers found an arched nasal crest previously associated with another dinosaur, the hadrosaurid Gryposaurusand. It was also around this time a peculiar lower jaw "shaped like two trowels laid side by side” was recognized.

New analysis revealed that the specimen belonged to a creature more primitive than the Gryposaurus.

Duck-billed dinosaurs, also called hadrosaurids, were the most common herbivorous dinosaurs at the end of the Mesozoic Era. They also had similar-looking snouts. Their front jaws meet in a U-shape to support a cupped beak they used to crop plants.

Some species have broader beaks, but until the Aquilarhinus was found, there was no evidence that showef hadrosaurids had beaks that varied in shape.

The Aquilarhinus, which was described in the Journal of Systematic Palaeontology on July 12, turned out differently. Unlike previously recognized duck-billed dinosaurs, its lower jaws meet in an odd W-shape that creates a wide, flattened scoop.

"This species is characterized by several autapomorphies of the facial skeleton and mandible, including a crest composed of broadly arched nasals. Notably, the symphyseal processes of the dentary are elongated and reflected dorsally, causing the dentaries to meet with a ‘W’-shaped anterior profile," researchers described the Aquilarhinus.

The main group of hadrosaurids called Saurolophidae commonly sported a bony cranial crests of varying shapes and sizes, but the Aquilarhinus, which is more primitive than the Saurolophidae, had a simpler a bony crest shaped like a humped nose.

Study researcher Albert Prieto-Márquez from the Institut Català de Paleontologia Miquel Crusafont, said the existence of the Aquilarhinus provided evidence that backs up the idea that the group had their origins in the southeastern area of the United States.

"This new animal is one of the more primitive hadrosaurids known and can therefore help us to understand how and why the ornamentation on their heads evolved, as well as where the group initially evolved and migrated from," Prieto-Márquez said.

The discovery of the new dinosaur and its crest also supports the idea that all crests were derived from a common ancestor that had a simple humped nose.