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Bird origins (1 Viewer)

Really Auk? You are going to publish paper that filled with arguments that were disproved a decade ago? There is a reason that many evolutionary biologists laugh when you mention Feduccia's arguments
 
Mysticete said:
Really Auk? You are going to publish paper that filled with arguments that were disproved a decade ago? There is a reason that many evolutionary biologists laugh when you mention Feduccia's arguments
Click to expand...

It's that bad? I've skimmed a bit of it and spent far more time than I have to spend on it this afternoon.
 
Mysticete said:
Really Auk? You are going to publish paper that filled with arguments that were disproved a decade ago? There is a reason that many evolutionary biologists laugh when you mention Feduccia's arguments
Click to expand...

I think your attitude is exactly what Fedducia and a few others are railing against:why are the proponents of birds are dinosaurs so resistant to question and why do they resort to such invective? Is the argument totally settled? Maybe Fedducia is not the best spokesperson for the anti movement, but that should not lead to the birds-are-dinosaurs proponents to suggest that their view is some sort of Truth. I suggest a good read of the uber-neglected James and Pourtless (Orntih. Monogr. 66)

Andy
 
The problem is that, well...sometimes there are reasons for certain views to be orthodox.

The James and Pourtless paper is...err...bad

For one, the outgroup sampling isn't sufficient to actually test whether birds are not dinosaurs, as they simply throw out most of the basal theropods/non maniraptoran theropods

Two, they a priori throw out most characters whose homology they are uncertain of (but only if the character would show a close relationship with dinosaurs...they do not seem to have an issue with the homology of other characters.

Some of this is unjustified; off the top of my head issues with digit homology have been resolved as a frame-shift mutation has been demonstrated in chicken hand development. There is also the issue that if you are doing a phylogenetic analysis, you will strongly bias the results if you throw out anything you are uncertain of homology wise. I have seen this done quite a bit in some of the older pinniped lit

Finally, if you want to test non-theropod origins, then you need a matrix that covers archosaurs in general. Sure, you can build it off a theropod tree, but IIRC they didn't bother adding other characters or even good exemplars of other archosaur groups.

I have heard other arguments about the paper, especially regarding the coding of Longisquama, which is a crushed fossil and which several of the codings might not be based on reality. For that matter some people think the elongate "quills" are actually plant material

Anyway, there is a reason that the paleontological community accepts the birds are dinosaur argument, and that is simply because it is the best fit for the character data.
 
Godefroit, P., Demuynck, H., Dyke, G., Hu, D., Escuillié, F., & Claeys, P. (2013). Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications, 4, 1394. doi:10.1038/ncomms2389
Abstract
 
Acrocephalus said:
Godefroit, P., Demuynck, H., Dyke, G., Hu, D., Escuillié, F., & Claeys, P. (2013). Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications, 4, 1394. doi:10.1038/ncomms2389
Abstract
Click to expand...

Thanks Mohamed!

I just love how the use of the word 'new' in the title stretches the definitions!
MJB;)
 
Kratter said:
I think your attitude is exactly what Fedducia and a few others are railing against:why are the proponents of birds are dinosaurs so resistant to question and why do they resort to such invective? Is the argument totally settled? Maybe Fedducia is not the best spokesperson for the anti movement, but that should not lead to the birds-are-dinosaurs proponents to suggest that their view is some sort of Truth. I suggest a good read of the uber-neglected James and Pourtless (Orntih. Monogr. 66)

Andy
Click to expand...

I have yet to encounter an explanation for what seems to me to be the simplest of bird/dinosaur origin questions - why did the "birds" (Archaeopteryx et al.) all evolve prior to the bird-like dinosaurs (Maniraptors and so on)? Whether it is proposed to be a Coelurosaur or Longisquama or whatever, I have heard of no real smoking gun has yet been identified as an Archaeopteryx ancestor.

The idea that "dinosaurs" are polyphyletic is a difficult and valid one to investigate, given the materials available (incidentally, I've felt that an evolutionary character as fluid as hip bones, over many millions of years, is a sketchy one to base a phylogeny upon). But "bird origins" and "birds are dinosaurs" are separate topics. I don't think anyone can argue that the maniraptors are descended from Archaeopteryx-like "birdosaurs," but what did those evolve from? Are maniraptors really dinosaurs? I think that is a more interesting question, and one that is far from settled yet.
 
Maniraptorans are certainly dinosaurs...in this case you have a shifting goalpost, where 20 years ago Fedducia and allies loudly and frequently proclaimed that Deinonychosaurs had nothing to do with birds. Now the evidence from numerous cladistic analyses is irrefutable on the relationships of maniraptorans, so suddenly the argument is deinonychosaurs are birds, but now maniraptorans have nothing in common with coelurosaurs.

As for the disrepancy in ages, we now have Middle and Late Jurassic Maniraptorans ( and possibly older creatures). Certainly the fossil record isn't the best, but then Coelurosaurs appear to have started off rather small, and combined with being terrestrial and having hollow bones, They don't preserve well. Archaeopteryx and the Chinese specimens all come from very specific depositional environments that favor detailed preservation. A lot of the famous Jurassic formations, like the Morrison, are not very kind to preservation of small critters (but even here we have a few maniraptorans, such as Ornitholestes and a bunch of more fragmentary material.

Similarly I have never heard any strong recent analysis of archosaur systematics which has suggested dinosaur paraphyly. I mean...the affinities of a few really weird creatures like Silesaurus and such have shifted into and out of dinosaurs, but nothing major like any of the recongized major dinosaur clades. Theropoda + Sauropodomorpha + Ornithischia appear to represent a real monophyletic group.
 
Also a collection of random points:

1. There are many many characters that link dinosaurs with birds, not just the hip

2. Feduccia (and I meant to correct this early) continues to argue that somehow birds = dinosaurs = ground up. This was true in the 80's among dinosaur researchers, but many dinosaur people now hold that an arboreal stage was likely for many dinosaurs

3. Similarly, Dinosaur origin proponents (Notably G.S. Paul) that some dinosaur groups might be secondarily flightless. This is still a minority viewpoint, but not something only argued by Birds are not dinosaurs people.
 
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