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Author Topic:   Theropods and Birds showing a change in kinds
Dr Adequate
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Posts: 16093
Joined: 07-20-2006
Member Rating: 8.9


Message 136 of 150 (545974)
02-06-2010 9:12 PM
Reply to: Message 135 by caffeine
02-06-2010 9:26 AM


Re: Phylogenetic nitpick
Wasn't pointing out a problem with your point, just being pedantic with the terminology. To continue a little bit further in that vein, Compsognathus isn't a maniraptoran. Here's the modern understanding of coelurosaur phylogeny (based on Senter (2007), from the wiki page on Coelurosauria:

Thanks. Now I'm all confused ... I used to know this once ...

Apologies to everyone if I've messed up my taxonomy. I'll edit my posts to put it right for posterity ... later.

Edited to add: I've just been looking at Wikipedia, and now I'm really confused. Because, apparently, so is everyone else.

The position of the Compsognathidae within the Coelurosaur group is uncertain; some hold the family as the basalmost of the coelurosaurs, while others as part of the Maniraptora.

Right. So what are the deinonychosauria and the dromaeosauridae?

Put it this way, what's the smallest clade containing both Deinonychus and Compsognathus?

Edited by Dr Adequate, : No reason given.


This message is a reply to:
 Message 135 by caffeine, posted 02-06-2010 9:26 AM caffeine has responded

Replies to this message:
 Message 137 by DC85, posted 02-06-2010 10:44 PM Dr Adequate has responded
 Message 139 by caffeine, posted 02-08-2010 4:36 AM Dr Adequate has not yet responded

  
DC85
Member (Idle past 435 days)
Posts: 875
From: Richmond, Virginia USA
Joined: 05-06-2003


Message 137 of 150 (545980)
02-06-2010 10:44 PM
Reply to: Message 136 by Dr Adequate
02-06-2010 9:12 PM


Re: Phylogenetic nitpick
it keeps changing and they're debated. The more they find the more diverse they seem to be. The line is sketchy just as the line between birds are. This is a wonderful example of diversity and evolution
This message is a reply to:
 Message 136 by Dr Adequate, posted 02-06-2010 9:12 PM Dr Adequate has responded

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Dr Adequate
Member
Posts: 16093
Joined: 07-20-2006
Member Rating: 8.9


Message 138 of 150 (546001)
02-07-2010 4:57 AM
Reply to: Message 137 by DC85
02-06-2010 10:44 PM


Re: Phylogenetic nitpick
It keeps changing and they're debated. The more they find the more diverse they seem to be. The line is sketchy just as the line between birds are. This is a wonderful example of diversity and evolution.

well then **** evolution and double **** the scientific method. What I want is complete certainty about everything forever. So, there, you did it, I'm going to become a creationist and from now on I'm going to give one sure and simple answer to every question, as follows: "The reason that it's that way is that God wanted it to be that way. And the cause that it's that way is that God did it by magic".

Screw reality, I'm going home.

Edited by Dr Adequate, : No reason given.


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caffeine
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Posts: 1624
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.2


Message 139 of 150 (546070)
02-08-2010 4:36 AM
Reply to: Message 136 by Dr Adequate
02-06-2010 9:12 PM


Re: Phylogenetic nitpick
Well it seems like I was speaking as if things are a lot more resolved than they reall are. From UCMP's page on Coelurosauria:

quote:
At this point they (Compsognathus and Ornitholestes) are considered incertae sedis; in other words, we know that they are theropods; and probably coelurosaurs; but we don't know who they are related to or how they fit into the big picture of theropod phylogeny.

This message is a reply to:
 Message 136 by Dr Adequate, posted 02-06-2010 9:12 PM Dr Adequate has not yet responded

  
caffeine
Member
Posts: 1624
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.2


Message 140 of 150 (546072)
02-08-2010 5:20 AM
Reply to: Message 123 by slevesque
02-05-2010 5:11 PM


Re: Feathers as novel features
The point is that at one point along the lineage the dinosaurs had only down feathers. Assuming that they evolved in a low-humidity environment is cool, but there isn't a lot of those isn't it. Care to give an example of such an environment ? Because it sounds to me the only place this would fit would be the desert.

There were more deserts in the Late Triassic and Early Jurassic than there are now, as a result of the big supercontinent leaving many regions a long way from the sea. These areas would also be subject to great temperature swings, and a trapped layer of air helps the body to not heat up too quickly in the day as well as not cool down too fast at night. A little bit of reading about down insulation on the web seems to suggest that you're right about it being pretty useless when wet. The consensus also seems to be that it's pretty much the supreme insulator when dry, however.

I can't access the link, but it's important not to mix up down feathers and 'dinofuzz'.

Sorry about the link - this one should work. And don't worry, I'm not getting feathers confused with simpler filaments. From the abstract:

quote:
Furthermore, the extensive feathering of this specimen, particularly the attachment of long pennaceous feathers to the pes, sheds new light on the early evolution of feathers and demonstrates the complex distribution of skeletal and integumentary features close to the dinosaurbird transition.

This only mentions pennaceous feathers, contour feathers like flight feathers; not the plumulaceous downy ones, but the body of the article seems to talk about these as well. This dinosaur is hardly unique though. Here's the discussion of Caudipteryx and Protoarchaeopteryx from an open-access journal that we can all read:

Two feathered dinosaurs from northeastern China

quote:
Wherever preservation made it possible, we found semi-plumes and downlike feathers around the periphery of the bodies, suggesting that most of the bodies were feather-covered, possibly like Archaeopteryx. Feathers found with Otogornis were also apparently plumulaceous. Plumulaceous and downy feathers cover the bodies of Protarchaeopteryx and Caudipteryx, and possibly that of Sinosauropteryx as well. This suggests that the original function of feathers was insulation.

Isn't beta-keratin a pretty common thing ? (My bio classes are far right now lol)

Reptiles scales contain beta-keratins too, but they're also constructed partly from alpha-keratins. In modern animals, bird feathers are unique in being composed almost entirely of beta-keratin, and this is something they seem to share with the filaments of Shuvuuia.

Edited by caffeine, : tags and typos


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xongsmith
Member
Posts: 1873
From: massachusetts US
Joined: 01-01-2009


Message 141 of 150 (546112)
02-08-2010 2:28 PM
Reply to: Message 140 by caffeine
02-08-2010 5:20 AM


Re: Feathers as novel features
Caffeine writes:
A little bit of reading about down insulation on the web seems to suggest that you're right about it being pretty useless when wet. The consensus also seems to be that it's pretty much the supreme insulator when dry, however.

And, remember - who said any of these sorts of features had to be optimal? They only had to be good enough.

Edited by xongsmith, : change period to question mark.


- xongsmith, 5.7d
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Taq
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Posts: 7693
Joined: 03-06-2009
Member Rating: 3.8


Message 142 of 150 (546226)
02-09-2010 12:23 PM
Reply to: Message 112 by slevesque
02-05-2010 3:58 PM


If birds are just dinosaur, how can anything be transitional between dinosaurs and birds ?

Obviously, we are talking about a transition between non-avian dinosaurs and avian dinosaurs.

Obviously, there are features that distinguish birds from their dinosaur ancestors. These are the ones that have to be shown transitional.

And that is exactly what we have in these transitionals. Archaeopteryx has teeth and a long tail which are non-avian dinosaur traits.

Non-avian dinosaur traits in Archaeopteryx:
1. Premaxilla and maxilla are not horn-covered (i.e. no beak).
2. Trunk region vertebra are free. In birds they are fused.
3. Cerebral hemispheres elongate, slender and cerebellum is situated behind the mid-brain and doesn't overlap it from behind or press down on it. In birds the cerebral hemispheres are stout, cerebellum is so much enlarged that it spreads forwards over the mid-brain and compresses it downwards.
4. Neck attaches to skull from the rear as in dinosaurs not from below as in modern birds.
5. Center of cervical vertebrae have simple concave articular facets. In birds the vertebrae are different, they have a saddle-shaped surface.
6. Long bony tail with many free vertebrae up to tip (no pygostyle).
7. Premaxilla and maxilla bones bear teeth.
8. Ribs slender, without joints or uncinate processes and do not articulate with the sternum. Birds have stout ribs with uncinate processes (braces between them) and articulate with the sternum.
9. Pelvic girdle and femur joint is archosaurian rather than avian (except for the backward pointing pubis as mentioned above).
10. The Sacrum (the vertebrae developed for the attachment of pelvic girdle) occupies 6 vertebra. The bird sacrum covers between 11-23 vertebrae.
11. Metacarpals (hand) free (except 3rd metacarpal), wrist hand joint flexible. In birds the metacarpals are fused together with the distal carpals in the carpo-metacarpus, wrist /hand fused.
12. Nasal opening far forward, separated from the eye by a large preorbital fenestra (hole). Where a fenestra is present in birds, it is always greatly reduced, and is involved in prokinesis (movement of the beak).
13. Deltoid ridge of the humerus faces anteriorly as do the radial and ulnar condyles. Typical of reptiles but not found in birds.
14. Claws on 3 unfused digits.
15. The fibula is equal in length to the tibia in the leg.
This again is a typical character of reptiles. In birds the fibula is shortened and reduced.
16. Metatarsals (foot bones) free. In birds these are fused to form the tarsometatarsus.
17. Gastralia present. Gastralia are "ventral ribs," elements of dermal bone in the ventral wall of the abdomen. Typical of reptiles, they are absent in birds.

cribbed from here

Hmf, that's a lot of non-avian features in a bird. But then there are also avian features:

1. Feathers.
2. Opposable hallux (big toe).
3. Furcula (wishbone) formed of two clavicles fused together in the midline.
4. Pubis elongate and directed backward.

So Archaeopteryx has a mixture of avian and non-avian features, just as one would expect if modern birds are descended from non-avian dinosaurs.


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Taq
Member
Posts: 7693
Joined: 03-06-2009
Member Rating: 3.8


Message 143 of 150 (546231)
02-09-2010 12:32 PM
Reply to: Message 122 by slevesque
02-05-2010 4:54 PM


I should have better expressed myself. What I mean is that if the fakes are well made enough to fool the paleontologists who examine it into thinking they are real and go up to the publishing.

Which paleontologists were fooled? In which scientific peer reviewed journal was this fossil presented as a real fossil? From what I have read National Geographic (not a peer reviewed scientific journal) presented this fossil without first checking with knowledgable paleontologists. In fact, Storrs L. Olson strongly criticized Nat Geo for publishing the article without it first going through peer review:

quote:
Writing in Backbone, the newsletter of his museum, he denounced the publication of a scientific name in a popular journal, without peer review, as a "nightmare".
http://en.wikipedia.org/wiki/Archaeoraptor

The only solution is that the publishers require CT scans on every fossil coming from china before publishing it.

The solution appears to be letting real paleontologists take a look at the fossil before letting art directors write stories about it.


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New Cat's Eye
Inactive Member


(1)
Message 144 of 150 (598326)
12-30-2010 11:02 AM


In Message 35, arachnophilia provided this information:

quote:
so, birds have two kinds of scales on their feet: reticulae (on the bottoms, the round reptilian scales) and the scutellae (flat plate-like scales on the top).

it turns out that the scutes have a strong relationship to feathers, and lacking a certain protein in development, become feathers. this likely means that birds have one gene that controls feather development all over their bodies, including their feet (such as in microraptor), and another that turns them off in particular places.

ie: the dinosaurian scales evolved from feather, not vice-versa.



  
arachnophilia
Member (Idle past 82 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 145 of 150 (598423)
12-30-2010 8:00 PM
Reply to: Message 142 by Taq
02-09-2010 12:23 PM


the reason archaeopteryx is a "bird"
taq writes:

cribbed from [talk origins]

oof, somebody needs to update t.o!

1. Feathers.

as noted in the other thread, this doesn't seem especially unique anymore. primitive feathers have even been found in ornithiscian dinosaurs, meaning that's almost certainly a non-avian dinosaur trait.

2. Opposable hallux (big toe).

as mentioned in the other thread, archaeopteryx does not have an opposed hallux. on most of the 7 specimens, the feet are a bit obscured, or twisted, and it was hard to tell. however, recent examination points out that the hallux is in precisely the same position and orientation as on other dromaeosaurid dinosaurs.

3. Furcula (wishbone) formed of two clavicles fused together in the midline.

furculae are about the first bones to disappear from dinosaur skeletons. but even coelophysis had one.

4. Pubis elongate and directed backward.

as in all dromaeosaurs. none of this stuff is particularly special. here are the avian characteristic of archaeopteryx from jacques gauthier's 1986 paper where he classifies avialae (his grouping of aves as not been generally well received) and comments by thomas holtz.

quote:
  1. Premaxillae elongate, narrow, and more pointed anteriorly, with longer nasal processes.

    [similar condition in bullatosaurs, and in the nondinosaurian Megalancosaurus, but unique to Archie and later birds in Maniraptora]

  2. Maxillary process of premaxilla reduced so that maxilla participates broadly in external naris (also in troodontids).

  3. Enlarged brain/basicranium (temporal musculature fails to extend origin onto frontal bones.

    [to a certain degree in bullatosaurs and therizinosauroids, and perhaps in some of the newer, "brainier" dromaeosaurids]

  4. Double-condyled quadrate displaced from distal position on opisthotic to more anteromedial position in contact with prootic.

    [Currie, pers. comm. and Walker, pers. comm., disagree with Whetstone's interpretation of the quadrate: Currie notes the anterior displacement of the quadrate in troodontids, and Walker does not consider the quadrate to be double-condyled in Archaeopteryx]

  5. Maxillary and dentary teeth reduced in size and number (or lost), with unserrated crowns and enlarged roots that completely enclose replacement teeth within them.

    [many of the smallest theropod teeth are unserrated, which may be a developmental constraint. The pinched roots of bird teeth are similar to those of troodontids, basal ornithomimosaurs, and (in at least a couple of cases) dromaeosaurids]

  6. Robust furcula for hypertrophied flight musculature .

    [true to a certain extent, although oviraptorids and (perhaps) some dromaeosaurids have substantial furculae as well, and even the new Morrison ?allosaurid seems to have a primitive furcula!]

  7. Scapula with more or less prominent acromion process for ligamentous connection to clavicle.

  8. Lenght/bredth ratio of scapula at midlength exceeds nine (not in penguins) and scapula tapers distally.

  9. Acrocoracoid tuberosity larger than in other coelurosaurs.

  10. Coracoid enlaged and inflected posteromedially more so than in other coelurosaurs.

  11. Very long forelimb and hands (e.g., in Archaeopteryx forelimb is 120-140% of hindlimb length, and more than twice as long as distance between glenoid and acetabulum), with forearm more than 87% of humerus length and mcII approaching or exceeding one-half of humerus length.

  12. Ischium compressed and dorsoventrally deep.

  13. Compared to other theropods, tibia, fibula, and metatarsals relatively more elongate with respect to femur, regardless of body size (mts short in penguins and some other birds).

    [Actually, as S. Gatsey and I have shown elsewhere, what actually is happening is a difference in the allometry of bird vs nonavian theropod hindlimbs. In nonavian theropods, the tibia/fibula and the metatarsus become relatively smaller as body size (and femur size) increases; in birds, the tibia/fibula and the metarsus become relatively longer as body size (and femur size) increases. Unfortunately, Archaeopteryx lies very close to the points at which the "bird" and "nonbird" allometric lines cross, so it is not possible to say at present to which of these curves the Urvogel belongs]

  14. Fibula attenuate distally, and may not extend to end of tibia.

  15. Proximal tarsals fused to tibia/fibula and to one another in adults.

    [also in some ceratosaurs]

  16. Distal tarsals and metatarsals fused at least distally in fully adult individuals (convergent in some ceratosaurs, elmisaurids, and Hulsanpes).

    [future work may show why this is no surprise for Hulsanpes...; also found in Avimimus]

  17. First pedal digit elongate and reversed (may be reversed in some extant birds).

    [the first "reversed" he uses is "reverted"; the second is "reversed" in the evolutinary sense]

  18. Metatarsal I attached on the distal quarter of metatarsal II.

  19. Tail reduced to no more than 23 free caudal vertebrae.

  20. Feathers cover limbs and tail, feathers on lateral margin of tail and posterior margin of arms enlarged, curved, and asymmetrically vaned, indicating aerodynamic function.

    [While it is true these features are currently only known in Archaeopteryx and later birds, there is only negative evidence with regards to this character in other theropods, as discussed in the paragraph immediately following his character list]

(source)


as you can see, it's pretty relative and arbitrary. and the more we learn about non-avian dinosaurs, the more similarities we have been finding -- which crosses a good number of these classification off the list.

Edited by arachnophilia, : No reason given.


אָרַח

This message is a reply to:
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Ronken 
Suspended Junior Member (Idle past 2694 days)
Posts: 5
From: China
Joined: 09-02-2011


Message 146 of 150 (631764)
09-02-2011 10:24 PM


Spammer
nice post ! thanks for sharing!!!

{The following message was spam and was deleted - Adminnemooseus}

Edited by Adminnemooseus, : Spam links deleted.

Edited by Adminnemooseus, : No reason given.


    
xongsmith
Member
Posts: 1873
From: massachusetts US
Joined: 01-01-2009


Message 148 of 150 (669847)
08-03-2012 11:22 PM


Is this article I found on Facebook relevant to this thread?

http://blogs.scientificamerican.com/...-reptileevolution-com


- xongsmith, 5.7d

Replies to this message:
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arachnophilia
Member (Idle past 82 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 149 of 150 (669850)
08-04-2012 12:05 AM
Reply to: Message 148 by xongsmith
08-03-2012 11:22 PM


not unless you believe this crackpot who makes david peters look positively academic.

אָרַח

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 Message 148 by xongsmith, posted 08-03-2012 11:22 PM xongsmith has acknowledged this reply

  
pandion
Member (Idle past 1104 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 150 of 150 (669970)
08-07-2012 12:56 AM
Reply to: Message 1 by New Cat's Eye
01-06-2010 12:39 PM


Right!
Sounds like a lizard, doesn't it?

Also sounds like a cat.

I'm just saying that a hiss isn't evidence of anything.


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