1 in 3 Dino Species Never Existed?

A controversial study by Jack Horner suggests that as many as one third of all known dinosaur species have been misidentified and do not represent actual species, but are actually just younger versions of larger species.
You may remember Jack Horner from his documentary Valley of the T.rex, where he argued the case that Tyrannosaurus was a scavenger as opposed to a hunter. Although what the documentary did not show was the evidence (which had been well known to Horner beforehand, suggesting a lack of documentary ethics on his behalf) which went against and even disproved his theory.
So long story short, he's back (along with Mark Goodwin) with his latest major study, which has taken the best part of ten years (not to mention big bucks TV deal). Some of you may be disappointed to hear that Nanotyrannus may no longer be a valid genus, but rather a juvenille Tyrannosaurus:

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

The evidence in this case is quite compelling, so it looks like Nanotyrannus will soon be stripped from the orthodox dinosaur genus list.

However, Horner and Goodwin's claims that 1 in 3 dinosaur species may not be valid has come under fire from other members of the palaeontological community. For example, Hans-Dieter Sues of the National Museum of Natural History in Washington D.C believes that their conclusions have been somewhat exaggerated.

National Geographic wrote:

"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."

Just how much time will be given to those in opposition to the theory in the upcoming documentary remains to be seen, but based on Horner's last effort (Valley of the T.rex) there probably wont be much (if indeed any).

Full article here.

A juvenille T.rex, or is it a Nanotyrannus?