Sydney: Scientists have discovered that an ancient hoofed mammal had very unusual features similar only to the nasal crests of lambeosaurine hadrosaur dinosaurs, showing a convergent evolution across millions of years between two very distantly related species.
Tyler Faith of University of Queensland, one of the study’s corresponding authors, and his colleagues started collecting fossils of ancient wildebeest-like animals in 2009 from a site called Bovid Hill in Australia’s New South Wales state.
“After several years of collecting fossils from Bovid Hill, it became very clear that most of the fossils belonged to the poorly known species Rusingoryx atopocranion, described from the same site in 1983, and that we may be dealing with an entire herd that was somehow wiped out and buried at the site,” Faith said.
In 2011, study co-author Kirsten Jenkins of the University of Minnesota found several intact skulls of the ancient animal during excavations at the site to establish why so many skeletons had ended up in that spot.
“I was astonished to see that (the skulls) looked unlike any antelope that I had ever seen – the only thing more surprising would have been fossil zebras with horns growing from their heads!” Faith said.
The similarity to hadrosaurs was immediately clear to the researchers when they opened CT scan files revealing the inner structures of those bones.
“We were expecting the inside of the dome to have something closer to normal mammalian anatomy, but once we took a look at the CT scans, we were pretty shocked,” said Haley O’Brien of Ohio University in Athens city in Ohio.
Based on their anatomical investigations together with acoustical modelling, researchers think the trumpet-like nasal tube may have allowed Rusingoryx to deepen its normal vocal calls.
In fact, their calculations suggest that the animals might have been able to call at levels very close to infrasound, such that other animals may not have been able to hear individuals in the herd calling back and forth to each other across fairly large distances.
The study findings were published on February 4 in the Cell Press journal Current Biology.