points for non dinosaurian ancestor of birds

[cambrian_exp]

recently i read in a book which suggested birds may have evovled from small lizard like ancestor rather than theropods. it said that,

fossils of earliest birds appear in mid-jurrasic period while its theropod feathered ancestor in early creteacous .

secondly reptiles started from five fingered ancestors, hence early dinosaurs retained this feature. but theropod retained only I II and III digits that is thumb index and middle finger while bird's fingers are reduced to 1 but recent embroynic studies has suggested that they have II III and V fingers . i.e index middle and last. ALL This suggests that although it has reptailian orgin birds didnt came from dinosaurs.

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all this was written in that rubbish book, and i m afraid of that. i personally belive dinosaurs were avian ancestors.. does any of u has any web site addresss which suggests non-dinosaurian ancestry of birds? forgive me for my poor english as it is not my first language, not also second. but third i m from india thats why

[Mokele]

All of that is two points, one of which can easily be explained by the spottiness and poor preservation in the fossil record. Coeleophysis may well have had feathers or protofeathers, but we just never found one that died in a situation that would have led to the preservation of that feature. We're almost *definitely* missing a large chunk of early bird evolution, simply due to the fact they were small, and small animals (with delicate bones) don't preserve as well and are less likely to fossilize.

 

As for the embryology, that really is a puzzler, no doubt, but given the masses of evidence *for* an avian origin, I suspect it's going to be sorted out when we figure out the "rules" and tendencies for how developmental patterns change in a macroevolutionary time scale.

 

Mokele

[Deathby]

Well if therapods evolved from five fingered reptiles, then obviously they would have 5 fingers in embryology, I don't see why there is a reason their ancestors definately wouldn't have it.

[cambrian_exp]

but what i mean to say is that theropods and birds may have evovled from common ancestor rather than birds from theorpods. thats why birds embroyoes retain II III and V digits of their ancestor's hands while theropods retain I II and III. Mokele i didnt understand your point. what do you mean by developmental patterns change in macro evolutionary time scale. do u mean to say that theropods had I II and III digits and when they changed to birds their pattern of hand also changed?

[Mokele]

Well, first, apparently early dinosaurs like Herrasaurus have all 5 digits, though 4 was reduced and 5 was just a split. Even the primitive ceratosaurian theropods, including coelophysis, has a full 4. Only the more advanced species had 3.

 

However, that said, there has been skepticism about the numbering of digits in birds, noted in an essay by G. Paul (http://www.dinosauria.com/jdp/archie/paulfed.html). I'm usually rather skeptical of his work, so I'd look into it more, but he does raise a valid point. This essay (http://www.biology.ualberta.ca/courses.hp/biol606/OldLecs/Lecture2K.04.Perry.html) also points out that the assignment of numbers to bird digits is problematic.

 

Mokele