A recent study conducted at the University of Utah has discovered that the elapsed time between the existence of early dinosaur relatives and the emergence of the first dinosaurs is much shorter than originally believed. The team of researchers utilized radioactive isotope measurements in order to date the zircon crystals found in Chañares Formation sediments, which are renowned for containing many fossils of early dinosaur relatives.
The fossils discovered in the formation were determined to be 234 to 236 million years old from the Late Triassic epoch, which is approximately 5 to 10 million years younger than our previous estimate of the age of the Middle Triassic epoch.
"To discover that these early dinosaur relatives were geologically much younger than previously thought was totally unexpected," Randall Irmis, who participated in the research, said in a press release.
Known for harboring the fossils of early dinosaur relatives, the Chañares Formation is approximately 75 meters thick and is made up of sediments from rivers, lakes and streams that existed during the Triassic period.
"Among Triassic geologic formations containing fossils, the Chañares Formation is a classic. It contains a variety of complete fossil specimens of early dinosauromorphs, which are essentially dinosaur aunts, uncles and cousins," said Irmis.
The results call into question various other timelines for other fossil-bearing formations around the world that were believed to stem from the Middle Triassic epoch, which will likely result in the dating of their radioisotopes in order to reevaluate their ages.
"We always thought these 'Middle Triassic' fossils showed the ecological recovery from the worst mass extinction of all time, the end-Permian extinction, but if these fossils are actually Late Triassic in age, they really have nothing to do with that recovery," Irmis said.
