July 17, 2019 1130 PM
BIG BEND NATIONAL PARK – Fossils unearthed 35 years ago in Big Bend National Park were recently identified as a new dinosaur species, Aquilarhinus palimentus. This duck-billed dinosaur is known for its aquiline nose and wide lower jaw, shaped like two trowels laid side by side.
The fossil was originally discovered in the 1980s by Texas Tech University Professor Tom Lehman. The bones were badly weathered and stuck together, making them impossible to study. Research in the 1990s revealed two arched nasal crests thought to be distinctive of the Gryposaurus genus. At that time the peculiar lower jaw was recognized, but it wasn’t until recent analysis that researchers came to realize that the specimen was more primitive than Gryposaurus and all other saurolophid duck-billed dinosaurs.
“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,” says lead author Dr. Albert Prieto-Márquez from the Institut Català de Paleontologia Miquel Crusafont, near Barcelona. “Its existence adds another piece of evidence to the growing hypothesis, still up in the air, that the group began in the southwestern area of the U.S.”
(Illustrations by ICRA Art)
Duck-billed dinosaurs, also known as hadrosaurids, were the most common herbivorous dinosaur at the end of the Mesozoic Era, and all had a similar looking snout. The front of the jaws meet in a U-shape to support a cupped beak used for cropping plants. The beak of some species is broader than others, but there was no evidence of a significantly different shape (and therefore likely a different feeding style) until Aquilarhinus was discovered. The lower jaws of Aquilarinus meet in a peculiar W-shape, creating a wide, flattened scoop. Around 80 million years ago, this particular dinosaur would have been shoveling through loose, wet sediment to scoop loosely-rooted aquatic plants from the tidal marshes of an ancient delta, where today lies the Chihuahuan desert.
The significance of this discovery includes that the jaw and other characteristics of the specimen show that it doesn’t fit with the group of duck-billed dinosaurs known as Saurolophidae. It’s more primitive than this group, suggesting there might have been a greater number of primitive species than previously recognized. Saurophids had a cranial crest and the current specimen also had a bony crest, shaped like a humped nose. The discovery of a solid crest outside the group supports the hypothesis that both types of crest evolved from a common ancestor.
These findings were recently published in the Journal of Systematic Paleontology, and is available at http://www.tandfonline.com/10.1080/14772019.2019.1625078. The study was funded by the Ramon y Cajal Program; the Ministry of Economy, Industry and Competitivity of Spain; the CERCA Program of the Generalitat de Catalunya; Texas Tech University; and the Sigma Xi National Scientific Honor Society.
The work was conducted under permit from Big Bend National Park, as well as the Texas Vertebrate Paleontology Collections at The University of Texas at Austin, where the specimen is housed.
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