RE: Dino/Birds? was Mesozoic snow? and fund for Antonio

[Jeff Hecht <jeff@jeffhecht.com>]

At 1:00 PM -0500 6/15/05, Tim Williams wrote:
>Jerry D. Harris wrote:
>
>>It is interesting that none of the classic Jehol Biota taxa have yet been 
>>recovered from the Daohugou (or, at least, not reported in any paper I have 
>>access to), but neither does the Dabeigou Formation (source of 
>>_Protopteryx_), and the latter is considered Early Cretaceous by most workers.
>
>Some authors have considered the Dabeigou Formation to be of Late Jurassic 
>age, possibly Tithonian (e.g., Chang and Park [2003]).  As you say, the 
>Dabeigou Fm is earlier than the Yixan Fm, which is in turn younger than the 
>Jiufotang Fm.  At least, that's my understanding.

So far, I am told there are very few tetrapod fossils from the Daouhugou, but 
there are plans to do more digging. 
>
>Andrew Simpson wrote:
>
>>I am shocked. We continously being told that all these theropods are 
>>feathered. The artists are putting feathers on everything thesedays. But you 
>>seem to be saying that we have only two theropods with proof of feathers?
>
>Tom and Mickey dealt with this already, but just to reiterate: there are 
>currently only two *Jurassic* theropods with proof of feathers.  These are 
>_Archaeopteryx_ and _Pedopenna_ - although the exact age of the latter is 
>still open to debate.  (I'm including _Jurapteryx_ and _Wellnhoferia_ in 
>_Archaeopteryx_, thereby giving us only one bird genus from the Solnhofen.)

Cladistically, there is a presumption that some sort of protofeather or 
dinofuzz evolved fairly far down the theropod family tree, so everything that 
is (say) above Sinosauropteryx had some kind of feather-ish body covering. But 
we don't know when that development occurred. The lack of evidence of feathers 
is not evidence of the absence of feathers. 
>
>BTW, the artists aren't putting feathers on theropods.  Evolution did that.
>
>>What is up with all those Dino-Birds in china. Are they flat out birds or is 
>>there some cross into the
>>dino realm?
>
>Birds evolved from theropod dinosaurs, and so in a phylogenetic context all 
>birds are dinosaurs.  Birds are dinosaurs, just as bats are mammals.  The term 
>'dino-bird' tends to apply to a nexus of theropod taxa that are close to the 
>base of the Avialae, such as _Microraptor_, _Caudipteryx_, or primitive birds 
>(like _Archaeopteryx_ or _Rahonavis_).  Some Chinese theropods are "flat out 
>birds" in the sense that their referral to the Avialae seems secure 
>(_Shenzhouraptor_, _Confuciusornis_, _Protopteryx_, _Yanornis_, etc), so they 
>are "true" birds.  On the other hand, taxa like _Microraptor_, 
>_Sinornithosaurus_, _Caudipteryx_ and _Beipiaosaurus_ usually fall outside the 
>Avialae, but are neverthless kissing cousins of the true birds.  _Dilong_ (a 
>tyrannosauroid) and _Sinosauropteryx_ (a compsognathid) are a little further 
>from the Avialae, phylogentically speaking.
>
I was told while writing my New Scientist feature that the theropod genera so 
far described from the Yixian formation are split roughly half and half between 
avian and non-avian forms. The birds generally are smaller, but the non-avian 
theropods are small by usual dinosaur standards. One of the things that's so 
wonderful about these deposits is that they contain a broad continuum of 
dino-birds, showing a range of evolution that had been little-known before.

-- 
Jeff Hecht, science & technology writer
jeff@jeffhecht.com; http://www.jeffhecht.com
Boston Correspondent: New Scientist magazine
Contributing Editor: Laser Focus World
525 Auburn St., Auburndale, MA 02466 USA
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