Roughly 75 million years ago during the Late Cretaceous, Rhinorex condrupus lived out its days eating plants in what is now Utah. This species was a hadrosaur, a family commonly regarded as duck-billed dinosaurs that generally had ornamental crests on top of their heads. While Rhinorex didn’t have the decorative crest, it did have a defining facial feature: an extremely large, hook-shaped nose. The research was led by Terry Gates of North Carolina State University, and the results were published in the Journal of Systematic Palaeontology.
From head to tail, Rhinorex was about 9.1 meters (30 feet) long, weighing in around 3,855 kilograms (8,500 pounds); nearly as much as a southern elephant seal. It has not been made abundantly clear why this species had such a large nasal arch, though it could have been used for social reasons.
"The purpose of such a big nose is still a mystery,” Gates said in a press release. “If this dinosaur is anything like its relatives then it likely did not have a super sense of smell; but maybe the nose was used as a means of attracting mates, recognizing members of its species, or even as a large attachment for a plant-smashing beak. We are already sniffing out answers to these questions."
Hadrosaurs have yielded some of the most abundant fossilized skin impressions of any dinosaur group, particularly near the Nelsen formation where this specimen was initially discovered in the 1990s. While Rhinorex’s bones had also been retrieved at that time, study of the skin took precedence and the bones were then tucked away into storage. Gates and co-author Rodney Sheetz of the Brigham Young Museum of Paleontology discovered the fossils and set to work describing them.
“We had almost the entire skull, which was wonderful,” Gates continued, “but the preparation was very difficult. It took two years to dig the fossil out of the sandstone it was embedded in – it was like digging a dinosaur skull out of a concrete driveway.”
This species was discovered relatively near two species of Gryposaurus, another hadrosaur with a large nose and a similarly-sized body. Because of the uncertainty value in dating Rhinorex, it isn’t entirely clear if they lived at the same time. Gryposaurus lived in an area that was much swampier than the one inhabited by Rhinorex, and it could have been variations in plant availabilities that caused these species to split from one another earlier in their evolutionary history. Rhinorex is the first hadrosaur skeleton to have been discovered in the Nelsen formation, which helps paleontologists understand the range.
“We’ve found other hadrosaurs from the same time period but located about 200 miles farther south that are adapted to a different environment,” Gates explained. “This discovery gives us a geographic snapshot of the Cretaceous, and helps us place contemporary species in their correct time and place. Rhinorex also helps us further fill in the hadrosaur family tree.”