Dino's to Birds

[Shawnster]

Well the fact that some dinosaurs HAD feathers kinda shows evidence that birds came from Dinos.

Interesting comment.

I found these two links that touch on this. Apparently there has been a bit of disagreement on which came first - feathers or scales.

http://www.dinosauria.com/jdp/archie/scutes.htm
Excerpt from the above link:

Unfortunately, this evidence can also support the theory of many ornithologists that birds share a common ancestor with the dinosaurs, rather than descend directly from the dinosaurs (thus making the birds the fourth group of the archosauria). If feathers are primitive for the group as a whole, there is no inherent reason to think birds had to descend from dinosaurs.



The debate on the subject of bird origins will continue, with ornithologists and dinosaurologists continuing to argue the significance of shared characters. However, this debate will include one new factor, the similarity of dinosaur feathers to bird feathers. Should the feathers of Sinosauropteryx prove to be very close to the down of birds, it may at last bring the doubters of the dinosaurian ancestry of birds into the fold.



The experiments of Zou and Niswander, and Alan Brush, suggest that scutes evolved from feathers. Although the research does not provide hints as to the origin of feathers, it does remove the impediment to the dinosaur-bird theory by showing that while feathers probably did not evolve from scales, scutes, a character shared by dinosaurs, may have evolved from feathers. Recent finds suggest, if not outright prove, that dinosaurs had feathers. Whether feathers are primitive characteristics of the archosaurs is a question that will continue to fuel the debate of whether birds are dinosaurs or a sister group to the dinosaurs. However, the results of the research of Brush and Zou and Niswander, and new finds such as the feathered dinosaur Sinosauropteryx, help strengthen the relationship between dinosaurs and birds.

And there is also this site http://www.scribd.com/doc/7175181/FeducciaJMorph266200542



Excerpt:

ABSTRACT The origin of birds and avian flight from within the archosaurian radiation has been among the most contentious issues in paleobiology. Although there is general agreement that birds are related to theropod dinosaurs at some level, debate centers on whether birds are derived directly from highly derived theropods, the current dogma, or from an earlier common ancestor lacking suites of derived anatomical characters. Recent discoveries from the Early Cretaceous of China have highlighted the debate, with claims of the discovery of all stages of feather evolution and ancestral birds (theropod dinosaurs), although the deposits are at least 25 million years younger than those containing the earliest known bird Archaeopteryx.


The frequently used phrase “birds are living dinosaurs” does little more than dampen research, because if it were true, then any fossil specimen with feathers in the Mesozoic would automatically be both a bird and a dinosaur. With the recent spectacular discovery of bird-like fossil footprints with a clearly preserved hallux from the Late Triassic (Melchor et al., 2002), Zhonghe Zhou (2004, p. 463) correctly notes, “it is probably too early to declare that ’it is time to abandon debate on the theropod origin of birds’ (Prum, 2002). Abandoning debate may succeed in concealing problems rather than finding solutions to important scientific questions.” The problem of avian origins is far from being resolved.

 

[Sean Aaron]

That's quite awesome! How old is she? My daughter (almost 5) is also a big dino-phile. Hopefully, she will never grow out of it. I certainly never did

She's 5; 6 in June.

I've always maintained an interest; it's only recently that I've decided to read more scientific literature. I'm currently reading more on athropods than dinosaurs, but I'm working my way there. Trilobite! (Fortey) was my inspiration to look out for more serious literature on palaeontology and evolutionary biology and this lead me to read Wonderful Life, Conway Morris's "rebuttal" Crucible of Creation (an odd read -- good for the science, but he clearly has almost and ID bent which seems bizarre for a man of science) and Big Cats and Their Fossil Relatives (Anton). The latter I cannot recommend enough. It's not terribly long but brilliantly written and has b&w and colour plates (even in softcover) by a scientific illustrator with a clear working knowledge of anatomy -- more books like this please!

@Shawnster: excellent find, clearly I'll have to temper my rhetoric a bit; the idea of feathers pre-dating scutes is something I wouldn't have expected and will be surprised if it's borne out by further research. Any comment Plix?

This in particular from the latter article is interesting and shows what little reading I've done on the topic. Some workers rather than stating that birds aren't descended from therapod dinosaurs or that what are described as feathers in recent Chinese fossils aren't feathers, instead challenge the current classification of feathered dinosaurs as dinosaurs and state rather that these animals should be recategorized as a new group of Dinosauromorpha, and having a common ancestor to dinosaurs, but actually being flightless birds rather than dinosaurs:

The bird-like nature of many maniraptoran theropods has not gone unnoticed over the years.

Recently,studies by Paul (2002), Czerkas et al. (2002), and Czerkas and Yuan (2002) have attempted to cut through the time-honored dogma and provide a possible starting point to a solution to the seemingly intractable problem of bird origins. They provide evidence that many of these early maniraptoran theropods are actually derived from the avian lineage and are therefore birds.

This view was first proposed by Abel (1911), and developed by George Olshevsky (Paul, 2002), and since the 1980s the theory has been developed by Gregory Paul. Most recently in a book entitled Dinosaurs of the Air, he argues that some theropods, including dromaeosaurids, troodontids, and oviraptorosaurids, are secondarily flightless birds.

In addition, Stephen Czerkas (2002) has promoted an avian origin from basal dinosauromorphs rather than theropods by his museum exhibits, and also in a book edited by Sylvia Czerkas entitled Feathered Dinosaurs and the Origin of Flight (Czerkas, 2002). Czerkas et al. (2002) describe Cryptovolans (Microraptor) as an ancestral dromaeosaur of pre-theropod, or non-theropod status. It has the typical dromaeosaur features of a stiffened “ramphorhynch-oid” tail, an enlarged second toe, and a retroverted pubis. However, given the probability that all microraptors had hindlimb wings attached to a short metatarsus, with long recurved pedal claws, they were probably precluded from being efficient ground-dwellers and would have been incapable of using the enlarged claw as a sickle claw for predation. It may, in fact, have been some type of climbing adaptation.

Microraptors, unlike true theropods, also lacked a supra-acetabular shelf (Martin,2004) for efficient bipedal locomotion, and had many avian features (Czerkas et al., 2002; Paul, 2002; Martin, 2004) (Figs. 27, 28), such as an avian hand and distal pubic spoon (hypopubic cup), as opposed to the dinosaurian pubic boot, to mention only a few. Most impressively, the hand bones of the wing are virtually identical to those of Archaeopteryx, if not more advanced (Fig. 27). Czerkas et al. (2002, p.118) correctly note that “both camps have portrayed dromaeosaurs incorrectly as dinosaurs…to support their…opposing views.”

Interestingly Dinosaurs of the Air is already one of my palaeontological wish list books on Amazon (thanks to a Paleontologica Electronica review -- recommended reading as a lot of stuff is being published here which you could normally only read in specialist print journals).

 

[Neopeius]

Trilobite! (Fortey) was my inspiration to look out for more serious literature on palaeontology and evolutionary biology and this lead me to read Wonderful Life

I read that last year and enjoyed it a lot. I've read a *lot* of negative criticism of that book, mostly on Gould's notion that fewer phyla means less diversity.

I didn't really get that from his book though. More like fewer phyla means different diversity. *shrugs*

 

[PlixTixiplik]

@Shawnster: excellent find, clearly I'll have to temper my rhetoric a bit; the idea of feathers pre-dating scutes is something I wouldn't have expected and will be surprised if it's borne out by further research. Any comment Plix?

Well, the cited article at that webpage doesn't actually discuss evolutionary implications and the conclusion drawn at the webpage doesn't make much sense. They say "When Zou and Niswander blocked certain proteins in embryonic chicks, feathers developed instead of scutes, strongly suggesting that feathers are the primitive characteristic." That would presuppose that evolution always proceeds by evolving new proteins to create morphological novelty, when in fact a variety of signaling mechanisms can be involved (including disuse of proteins or protein blocking). In fact, as summarized in a more recent review article, all of the molecular, developmental, and fossil evidence suggests that feathers are the derived character.

Furthermore, to have feathers as the ancestral character of Dinosauria (or of Archosauria) would mean that feathers would have to be lost multiple times in different lineages. It would also mean that the ancestor of crocodiles had feathers. Longisquama is a common basal archosaur that has been argued to be a bird ancestor (or related to "proto-birds"), but that is pretty ridiculous (one person has gone as far as to say "there is nothing in Longisquama's morphology that is inconsistent with a protobird.") Nothing inconsistent except for the fact that Longisquama lacks all of the bird-like skeletal characteristics (wishbone, pneumatic bones, moon-shaped wrist bone, feathers, and dozens of others)! The argument mainly hinges on the assumption that flight must have evolved through a gliding, arboreal stage (probably wrong in the case of birds) and the assumption that elongate scales in Longisquama evolved into feathers (almost certainly wrong given the developmental work on feathers). If you actually do the cladistics rather than picking and choosing a few characters and ignoring all of the others, the basal archosaur origin of birds has no support.

This in particular from the latter article is interesting and shows what little reading I've done on the topic. Some workers rather than stating that birds aren't descended from therapod dinosaurs or that what are described as feathers in recent Chinese fossils aren't feathers, instead challenge the current classification of feathered dinosaurs as dinosaurs and state rather that these animals should be recategorized as a new group of Dinosauromorpha, and having a common ancestor to dinosaurs, but actually being flightless birds rather than dinosaurs:

The bird-like nature of many maniraptoran theropods has not gone unnoticed over the years.

Recently,studies by Paul (2002), Czerkas et al. (2002), and Czerkas and Yuan (2002) have attempted to cut through the time-honored dogma and provide a possible starting point to a solution to the seemingly intractable problem of bird origins. They provide evidence that many of these early maniraptoran theropods are actually derived from the avian lineage and are therefore birds.

This view was first proposed by Abel (1911), and developed by George Olshevsky (Paul, 2002), and since the 1980s the theory has been developed by Gregory Paul. Most recently in a book entitled Dinosaurs of the Air, he argues that some theropods, including dromaeosaurids, troodontids, and oviraptorosaurids, are secondarily flightless birds.

In addition, Stephen Czerkas (2002) has promoted an avian origin from basal dinosauromorphs rather than theropods by his museum exhibits, and also in a book edited by Sylvia Czerkas entitled Feathered Dinosaurs and the Origin of Flight (Czerkas, 2002). Czerkas et al. (2002) describe Cryptovolans (Microraptor) as an ancestral dromaeosaur of pre-theropod, or non-theropod status. It has the typical dromaeosaur features of a stiffened “ramphorhynch-oid” tail, an enlarged second toe, and a retroverted pubis. However, given the probability that all microraptors had hindlimb wings attached to a short metatarsus, with long recurved pedal claws, they were probably precluded from being efficient ground-dwellers and would have been incapable of using the enlarged claw as a sickle claw for predation. It may, in fact, have been some type of climbing adaptation.

Microraptors, unlike true theropods, also lacked a supra-acetabular shelf (Martin,2004) for efficient bipedal locomotion, and had many avian features (Czerkas et al., 2002; Paul, 2002; Martin, 2004) (Figs. 27, 28), such as an avian hand and distal pubic spoon (hypopubic cup), as opposed to the dinosaurian pubic boot, to mention only a few. Most impressively, the hand bones of the wing are virtually identical to those of Archaeopteryx, if not more advanced (Fig. 27). Czerkas et al. (2002, p.118) correctly note that “both camps have portrayed dromaeosaurs incorrectly as dinosaurs…to support their…opposing views.”

Interestingly Dinosaurs of the Air is already one of my palaeontological wish list books on Amazon (thanks to a Paleontologica Electronica review -- recommended reading as a lot of stuff is being published here which you could normally only read in specialist print journals).

The only way they can make these arguments is by picking and choosing a few characters and a few taxa, and ignoring the rest of the data. They don't use a rigorous cladistic framework to frame their hypotheses (Feduccia is particularly bad in this respect). If you consider all of the characters, and perform a cladistic analysis, Aves remains monophyletic with dromaeosaurs and troodontids as its sister group (like in the cladogram below), and all are well supported as derived theropods. It does seem likely that some dromaeosaurs were secondarily flightless, but that doesn't mean they evolved from birds (it's a common misconception to conflate the origin of birds and the origin of flight, when the two are not necessarily linked). The theropod group that most often has fallen within Aves is an unusual group called Alvarezsauria, but its position has been poorly resolved and tends to bounce around a lot because there are few taxa and most are heavily derived. More recently it seems to be settling down within Maniraptora somewhere.

 

[Sean Aaron]

Trilobite! (Fortey) was my inspiration to look out for more serious literature on palaeontology and evolutionary biology and this lead me to read Wonderful Life

I read that last year and enjoyed it a lot. I've read a *lot* of negative criticism of that book, mostly on Gould's notion that fewer phyla means less diversity.

I didn't really get that from his book though. More like fewer phyla means different diversity. *shrugs*

I disagree with a lot of Gould's ideas, punctuated equilibrium being one of them and much of what he wrote about the animals in Wonderful Life was later refuted by additional fossil finds from China which shows that both Opabinia and Anomalocaris were both lobopodians and closely related, so his notion of creating more phyla wasn't borne out. However I think the book is still valuable for putting the history of the Burgess Shale finds into a proper historic perspective and challenging the traditional view of evolution as a "progression to perfection" with the living being superior to the extinct and humanity being the apex of all lineages.

Well, the cited article at that webpage doesn't actually discuss evolutionary implications and the conclusion drawn at the webpage doesn't make much sense. They say "When Zou and Niswander blocked certain proteins in embryonic chicks, feathers developed instead of scutes, strongly suggesting that feathers are the primitive characteristic." That would presuppose that evolution always proceeds by evolving new proteins to create morphological novelty, when in fact a variety of signaling mechanisms can be involved (including disuse of proteins or protein blocking). In fact, as summarized in a more recent review article, all of the molecular, developmental, and fossil evidence suggests that feathers are the derived character.

Furthermore, to have feathers as the ancestral character of Dinosauria (or of Archosauria) would mean that feathers would have to be lost multiple times in different lineages. It would also mean that the ancestor of crocodiles had feathers. Longisquama is a common basal archosaur that has been argued to be a bird ancestor (or related to "proto-birds"), but that is pretty ridiculous (one person has gone as far as to say "there is nothing in Longisquama's morphology that is inconsistent with a protobird.") Nothing inconsistent except for the fact that Longisquama lacks all of the bird-like skeletal characteristics (wishbone, pneumatic bones, moon-shaped wrist bone, feathers, and dozens of others)! The argument mainly hinges on the assumption that flight must have evolved through a gliding, arboreal stage (probably wrong in the case of birds) and the assumption that elongate scales in Longisquama evolved into feathers (almost certainly wrong given the developmental work on feathers). If you actually do the cladistics rather than picking and choosing a few characters and ignoring all of the others, the basal archosaur origin of birds has no support.

No question, if you read all the pieces together it's a refutation of the initial work done identifying the fossil structures and it challenges the notion of the evolution of flight in birds being from the ground up -- though I agree with them that characterising Archaeopteryx as a hopping raptor makes little sense. Taken together it does seem to be a concerted political reaction against the Aves as Maniraptoran argument despite it being stated repeatedly that they're interested in the science alone.

The only way they can make these arguments is by picking and choosing a few characters and a few taxa, and ignoring the rest of the data. They don't use a rigorous cladistic framework to frame their hypotheses (Feduccia is particularly bad in this respect). If you consider all of the characters, and perform a cladistic analysis, Aves remains monophyletic with dromaeosaurs and troodontids as its sister group (like in the cladogram below), and all are well supported as derived theropods. It does seem likely that some dromaeosaurs were secondarily flightless, but that doesn't mean they evolved from birds (it's a common misconception to conflate the origin of birds and the origin of flight, when the two are not necessarily linked). The theropod group that most often has fallen within Aves is an unusual group called Alvarezsauria, but its position has been poorly resolved and tends to bounce around a lot because there are few taxa and most are heavily derived. More recently it seems to be settling down within Maniraptora somewhere.

Agreed. I was thinking about this over the weekend and dromeosaurs as flightless birds just makes no sense to me. It's like the exercises people have gone through to position trilobites as chelicerates using the antennae as homologues for chelicera. There is one other characteristic that points to a trilobites-chelicerate affinity, but in order to make it work you need to be a taxonomic contortionist and ignore the characterists that are against it. Ah, the difficulties of the taxonomist!

It seems like one of the factors causing some opposition is the position of Archaeopteryx as a flying bird-like animal with no decendents, which reduces its significance as the "first bird." As you say though, unless some kind of feathered basal archosaur could be found, the case for birds evolving side-by-side with dinosaurs is difficult to make.

Likewise birds as theropods would be more solid with more Jurassic transitional forms between the ancestor of archaeopteryx and the dromeosaurs.

Dromeosaurs as birds I could take more seriously if someone turned up a dromeosaur with a beak, but I find that extremely unlikely.

In time hopefully someone will make another radical discovery that will put the world right. In the meantime the dispute will continue...

 

[Neopeius]

Trilobite! (Fortey) was my inspiration to look out for more serious literature on palaeontology and evolutionary biology and this lead me to read Wonderful Life

I read that last year and enjoyed it a lot. I've read a *lot* of negative criticism of that book, mostly on Gould's notion that fewer phyla means less diversity.

I didn't really get that from his book though. More like fewer phyla means different diversity. *shrugs*

I disagree with a lot of Gould's ideas, punctuated equilibrium being one of them and much of what he wrote about the animals in Wonderful Life was later refuted by additional fossil finds from China which shows that both Opabinia and Anomalocaris were both lobopodians and closely related, so his notion of creating more phyla wasn't borne out. However I think the book is still valuable for putting the history of the Burgess Shale finds into a proper historic perspective and challenging the traditional view of evolution as a "progression to perfection" with the living being superior to the extinct and humanity being the apex of all lineages.

Exactly. And it's okay for Gould to be wrong. Lots of people have been wrong.

I think the idea of punctuated equilibrium is important even if it's not a complete model, any more than natural selection is a complete model.

 

[warriorsfan]

http://www.geocities.com/jimspace3000/dinosaur.htm.

I found this link to be interesting. No, it does not address the scales vs. feathers or dinosaurs vs. birds question, but it still gives some interesting references to the dinosaur evolution question.

1996 called, it wants its webpage design back.

Speaking of extinction, I thought geocities went extinct 10 years ago!

 

[Sean Aaron]

Just to further the derailment, I actually considered a geocities website, but then realised a blog was a whole lot easier to deal with.

 

[Sean Aaron]

Well, this new find seems to nicely turn a lot of suppositions upside down.

An ornithischian has been found to apparently have some kind of feather or "proto-feather" body covering:

http://news.bbc.co.uk/1/hi/sci/tech/7950871.stm

So, this suggests that feathers are a derived characteristic from a dinosaur that pre-dates the saurischian - ornithischian split and may fuel the debate over whether or not birds are indeed decended from the saurischian therapod line or if they are from a separate lineage of archosaurs...

 

[flux_29]

But wern't dinosaurs "warm blooded" reptiles? A few in the bird family havig feathers sure, but stegosaurus and diplodicus?

 

[Sean Aaron]

But wern't dinosaurs "warm blooded" reptiles? A few in the bird family havig feathers sure, but stegosaurus and diplodicus?

There's never been consensus on whether or not any dinosaurs were "warm blooded" and when an animal gets as big as a diplodocus it's possible for it to regulate body temperature without having the higher metabolism of a mammal.