What if a third of “known” dino species never really existed?
What’s a little kid to do with all those different dinos he can identify on sight?
“…The lean and graceful Nanotyrannus is one strong example. Thought to be a smaller relative of T. rex, the supposed species is now considered by many experts to be based on a misidentified fossil of a juvenile T. rex.
The purported Nanotyrannus fossils have the look of a teenage T. rex, Horner said in the new documentary. That’s because T. rex’s skull changed dramatically as it grew, he said.
The skull morphed from an elongated shape to the more familiar, short snout and jaw, which could take in large quantities of food.
But the smoking gun, Horner said, was the discovery of a dinosaur between the size of an adult T. rex and Nanotyrannus.
Nanotyrannus—actually a young T. rex in Horner’s view—had 17 lower-jaw teeth, and an adult T. rex had 12.
The midsize dinosaur had 14 lower-jaw teeth—suggesting that it was also a young T. rex, and that tyrannosaurs gradually traded their smaller, blade-like teeth for fewer bone-crushing grinders in adulthood…Hans-Dieter Sues, a paleontologist at the National Museum of Natural History in Washington, D.C, said that scientists discovered in the 1970s that some duck-billed dinosaur species were in fact animals in different stages of maturity—representing a smaller number of species.
Sues, who was not involved in the new research, agrees that some dinosaur species from the late Cretaceous may prove to be juveniles of other species.
“Many dinosaurs—just like many present-day vertebrates—changed a lot in their appearance as they grew up,” he said.
But “some of [these] conclusions are controversial,” Sues cautioned, adding that the idea that up to a third of all species may be reclassified is an exaggeration.
In fact, Sues suspects that a second wave of dinosaur extinction is unlikely—unless, that is, fossil hunters hit the jackpot.
“Testing such hypotheses is difficult,” he said, because “it requires more fossil material than is currently available.”…”