09 February 2006

Instant feathers?

Now here’s an interesting piece of journalism:

Although G. wucaii’s skeletal features are very similar to later tyrannosaurs, it had three fingers, instead of the two found on most advanced tyrannosaurs. Also, it was likely as feathered as a chicken.

Feathered as a chicken? Interesting... the LiveScience article it’s based on says:

Paleontologists have unearthed two fossilized dinosaurs believed to be the oldest ancestors of the tyrannosaur family, researchers announced today.

The new species had cranial crests and were likely covered in feathers, but were only a third the size of their famous cousin, Tyrannosaurus rex.

Still, the discovery sets back the clock on the tyrannosaur family by at least 30 million years.

The articles are accompanied by this picture, which shows some kinda-sorta fluffy proto-feather things:

dino little

Now... back to the source Nature article, which... doesn’t mention features at all? What happened? Where did the feathers come from?

It turns out that between Xu’s report and Carey’s news item, we find the long-sought intermediate species: a news blurb in the same issue of Nature magazine, which waxes lyrical (as you’d expect) and touches on “simple fuzzy ‘protofeathers’ ” on a different species of dinosaur. Aiy-ay-ay!

But wait! There’s more! (-:

The species in question is dilong paradoxus so I went dinosaur hunting, and turned up a National Geographic article from a bit over a year ago, with pictures. The discoverer was the same Mr Xu, and the article says (under the heading “Down Coat”):

The description of Dilong paradoxus is based on the fossils of four specimens, including a fragmented one with evidence of protofeathers — precursors to the feathers found on modern birds.

So... four fossils, one of which had evidence of, the article says later, “hairlike structures”.

Hairlike structures? Where’s the feathers? The picture shows an animal which looks for all the world like a large rooster (birdlike feet and all, but Xu says nothing about the feet) with a Rex head grafted on.

Summary so far: one sample of a relative of this dinosaur had evidence of “hairlike structures” — and suddenly every dinosaur in sight is fully fledged and ready to crow.

There’s also input here from Mr Holtz (remember him from Nature above? — square backets in original):

if the early feathers of Sinosauropteryx and the feathers of birds and other feathered dinosaurs are all expressions of the same evolutionary change, “then we have to infer that tyrannosaurids also had some expression of the same trait [feathers].”

“To infer otherwise would be invoking an evolutionary change for which we had no evidence,” he said.

OK, so Holtz wants there to be feathers everywhere and is prepared to invert the burden of proof in order to make it so; stack this on top of Xu’s propensity for occasionally describing “hairlike structures” as “protofeathers” and we’re well on our way. Chinese (hah!) whisper that through one more barrow-pushing layer (Carey) and — tah-daah! — elusive traces of hairlike stuff have become grandma’s feather bed, with claws.

If this kind of mutation happens so quickly in relatively hard science disciplines, it makes you wonder (correction, it makes me wonder) what manner of hair-raising transmogrifications take place in less peer-reviewed information domains like, say, IT magazines.

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