What is the current thinking behind dino/bird evolution?

I don't claim to be particularly learned on this subject, but it is one that I find very interesting.

Since I last posted to this group, something like 6 years ago, I have been aware of new fossils being discovered in China and Mongolia that have birdlike feathers and a theropod skeleton.

What is the current thinking on the possible link between Birds and Dinosaurs?

Tony Hedges.

John Ostrum, Professor Emeritus of Yale University (Peabody Museum) has been a leading proponent of the dinosaur/bird hypothesis. He is also the leading expert on achaeopteryx. I would suggest looking up some of his literature for more information. As for me, I think there is a connection, but more fossils are needed to make the evidence compelling.

Hardly, IMO. A few hundred carefully-documented synapomorphies is plenty to convince me. The amount of evidence for the link is many times *more* the amount of evidence for most other links in biology, and simply cannot be explained away ... what other idea could account for all the massive similarities convincingly? Not convergent evolution, certainly

With a few outspoken exceptions, vertebrate paleontologists agree that birds are descended from dinosaurs, and hence should be regarded as specialized archosaurs.

Although not the most readable analysis of the scientific evidence, Brochu's 'Progress and future directions in archosaur phylogenetics' [Journal of Paleontology, 2001, 75(6)] is a good treatment of the subject. Padian and Gauthier have also written extensively on the subject.

As I said, I think there is a conection. Being a scientist, I like to hedge my bets until the obese lady sings. Its safer that way.

I don't claim to be very learned on this subject either, but I offer the following:

There has been a great deal of discussion related to how the dinosaurs that evolved feathers for warmth developed flight. In order to fly like birds or even to glide, they had to have flight feathers on their forelimbs, and flight feathers are quite different from 'warmth' feathers.

All of the pictures I have seen of theropod remains showed that they had quite long tails, probably to help their balance as they jumped, kangaroo-like while chasing their prey. All of the feathered ones also had a fan of flat feathers on the end of the tail. I propose that the fan developed because the tail moved up and down in synchrony with the jumping motion. At first it provided only balance, but later flatening and adding feathers providing a bit of thrust. Wing feathers came along later, first providing steering and making the jumps into glides, then adding propulsion as the feathers got larger. It seems to me that with wings to provide lift, and tail to provide thrust, flight could have existed for a long time using this method before bird type flight came along.

The tail motion, at first, was very similar to the swimming motion of whales and dolphins.

Incidentally, how might I get Professor Ostrum to read this? I would like to have his reaction to it.

George Prehmus

I'm afraid you'll have to write him the old fashion way. I'm sure he would answer your letter. He's a great guy. By the way, your theory sounds interesting except for one thing. The oldest known bird, archaeopteryx, had wing and tail feathers. No fossils have been found ONLY with tail feathers. To say that wing feathers came along after tail feathers just doesn't jibe with the current fossil record as it is known today. Perhaps some day someone will prove you right by finding a fossil with only tail feathers, and no hint of structures related to feathers on the forelimbs. But as of today, that is not the case.

Don't worry about it. The case is wrapped up. It is a fact of the Universe. Birds are living dinosaurs. There are lots of fossils from China which are clearly intermediates on the evolutionary line of

I don't want to sound like Cal or anything but all those fossils from china are from well after the emergence of true birds. I would be much more sanguine about the BAD theory if we could find some fossils contemporary with or preceding Archaeopteryx.

Birds were already considered archosaurs before the dino-link was established.

Don't you mean specialized dinosaurs?

Hence, I hedge my bets, and wait until the obese lady sings.