Dino's to Birds

[Kaziarl]

So we were watching Jurassic Park. I know, not scientifically accurate, but it does make me think of some questions.

1) Do you think Dinosaurs evolved into Birds?
2) If yes, what would be the reason for the evolutionary jump from scales to feathers.

My significant other suggested warmth, but would fur be better?

 

[PlixTixiplik]

Yes, dinosaurs evolved into birds. In addition to the feathers, there are three other lines of evidene: osteology (bones), oology (eggs), and behavior. Theropods and birds share a wishbone (which gradually changed from boomerang to horseshoe-shaped), moon-shaped wrist bone, bony ventral ribs, things called "uncinate processes" on their ribs (used in breathing), and of course feet with three major digits. The bird-like breathing system, with gas sacs in hollow bones, also evolved in basal theropods. Dinosaurs, and theropods in particular, have bird-like bones with a lot of spongy medullary bone indicating rapid growth.

In terms of eggs, theropods and birds also have what is called asynchronous ovideposition, which means they lay their eggs one at a time rather than in one big dump (as crocodiles and sauropod dinosaurs do). In the case of theropods, they still had two functioning oviducts so laid two eggs at a time (there is a fossil from China preserved in the act of laying eggs). Theropods and birds also the only groups to have a secondary eggshell layer composed of laminar calcite in addition to the inner layer composed of radial fans of calcite. They also are the only groups to have non-spherical eggs, and asymmetrical eggs evolved in an advanced group of theropods called Eumaniraptora.

As for behavior, theropods brooded their eggs just like birds do (rather than covering the clutch with dirt or plant material like crocodiles and sauropods did). There are specimens from the Gobi desert preserved brooding a clutch of eggs. There is also a specimen of a theropod from China preserved sleeping with its head tucked under its wing like birds do.

There are several possible explanations for the evolution of feathers - warmth is one although the bone structure and presence of avian breathing system even in basal theropods suggests they had pretty active metabolisms (maybe not as active as birds, but close). Also, many theropods were large so could have maintained a relatively constant body temperature just by virtue of their large size (and resulting low surface area:volume ratio). Others have suggested that they used wing feathers as a net or something to stun flying insects, which they then ate. But consider that the first stage in feather evolution was downy feathers (in a group called Coelurosauria, which includes Tyrannosaurus and its ancestors) - not a very good "net." To me, the most plausible explanation is that they were for display during mating. There is a genus of basal birds called Confuciusornis (basal member of a group sometimes called Pygostylia, the next most exclusive group after truly basal birds like Archaeopteryx) that displays sexual dimorphism, with the (presumably) male having two long tail feathers.

Downy feathers evolved first, and then symmetrical vaned feathers appeared in Maniraptora (includes oviraptorids, dromaeosaurs, troodontids, and birds), and finally asymmetrical vaned feathers evolved in Eumaniraptora (excluding oviraptorids). Even though early members of Maniraptora couldn't fly, there would be selective pressure to lengthen feathers and improve their aerodynamics because flapping while running could increase their running speed (modern ground-dwelling birds like Chukars do this - wing-assisted running). It was only when they became small enough that they could fly, and flight appears to be the ancestral character for Eumaniraptora (also called Paraves, I'm not clear on the difference) - including all dromaeosaurs, troodontids, and birds. All of the taxa that are basal to those groups (such as Mahakala, Shanag, Mei, Jinfengopteryx, Sinovenator, Microraptor, Graciliraptor) are crow or eagle-sized. So the large Deinonychus, Velociraptor, and Troodon were secondarily flightless, having evolved from small flying (albeit poorly flying) ancestors - the ostriches of the Cretaceous!

-MEC

 

[Neopeius]

You are a fine poster, always a pleasure

 

[Chess Piece Face]

So we were watching Jurassic Park. I know, not scientifically accurate, but it does make me think of some questions.

1) Do you think Dinosaurs evolved into Birds?
2) If yes, what would be the reason for the evolutionary jump from scales to feathers.

My significant other suggested warmth, but would fur be better?

Take any one credit Dinosaurs course at your local college and you will have your answer.

 

[Sean Aaron]

Birds are dinosaurs would be my position on it -- they're the decendents of the survivors of the extinction. I see no reason to make a distinction between them, personally, though I know some would regard this as controversial.

 

[PlixTixiplik]

Birds are dinosaurs would be my position on it -- they're the decendents of the survivors of the extinction. I see no reason to make a distinction between them, personally, though I know some would regard this as controversial.

In a phylogenetic sense that is absolutely correct, but a lot of our taxonomic names, especially in popular usage, are paraphyletic groups that don't include a common ancestor and all of its descendants. For example, birds also technically belong to Reptilia but we wouldn't traditionally think of them as reptiles. The history of modern bird groups (crown-group Neornithes) is actually quite controversial - some argue that they diversified rapidly after the end-Cretaceous extinction (no modern bird groups are known from Mesozoic fossils) but others think they were present before (molecular clocks suggest divergence about 100 myr). Birds were quite diverse and probably fairly abundant in the Mesozoic, but were dominated by stem-group taxa and this diverse extinct group called Enantiornithine birds.

Cladistics has been a great tool to reconstruct monophyletic groups (those containing a common ancestor and all of its descendants) but because they're like those Russian dolls with one inside the other it has resulted in a proliferation of names (for example, modern Neornithine birds belong to the clade Ornithurae, which nests within Ornithothoraces, which belongs to Pygostylia, which is in Aves, which is in Eumaniraptora, in Maniraptora, in Coelurosauria, in Tetanurae, in Neotheropoda, in Theropoda, in Saurischia, in Dinosauria...). It's certainly more precise and accurate for taxonomists, but it results in a confusingly large amount of names for non-specialists.

 

[flux_29]

http://en.wikipedia.org/wiki/Feathered_dinosaurs

http://en.wikipedia.org/wiki/Archaeopteryx

http://en.wikipedia.org/wiki/Origin_of_birds

 

[Meredith]

I saw an interesting program on the Discovery Channel where they worked to re-activate some genes that had been suppressed by birds that were active in Dinosaurs. Cool Stuff! Birds did retain scales for covering their feet and anything else not covered by feathers.

The Idea of a small dinosaur derived from a chicken makes me giddy, after a few hundred million years of small mammals being eaten by Dino-birds, time for some tasty revenge!!!!

 

[Alpha_Geek]

The US PBS show "NOVA" had an interesting episode tonight on a landmark court case here in the us on Intelligent Design vs Evolution.

It should be here:
http://www.pbs.org/wgbh/nova/programs/
when it's posted for online viewing.

Why I bring it up here is that part of the legal argument was that the ID contenders claimed no transitional creatures (feathered dinos, etc) existed in the fossil record, but those claims were refuted with lots of evidence.

 

[Kaziarl]

This was sent to my pm box. The poster seemed to want annonimity, so i'll leave the name out. I just felt it added to the discussion.

Since equal time for opposing views seems to be frowned upon by some vocal board members, I thought I'd send you this in PM.

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.

 

[Psion]

The US PBS show "NOVA" had an interesting episode tonight on a landmark court case here in the us on Intelligent Design vs Evolution.

It should be here:
http://www.pbs.org/wgbh/nova/programs/
when it's posted for online viewing.

Why I bring it up here is that part of the legal argument was that the ID contenders claimed no transitional creatures (feathered dinos, etc) existed in the fossil record, but those claims were refuted with lots of evidence.

That was an amazing episode! I caught it at 2:00am this morning after waking from a bad cold, and it was absolutely riveting. I understood the motives of the folks with religious views in the Dover school district, but the lies, subterfuge, and ultimately threats of violence against the (Bush appointed!) judge sure seemed decidedly unChristian. I loved the takedown on irreducible complexity and the flagellum example.

Coincidentally, there was an advertisement for the next episode, "The Four-Winged Dinosaur" ... dealing with the evolution of birds at the end.

 

[Sean Aaron]

Cladistics has been a great tool to reconstruct monophyletic groups (those containing a common ancestor and all of its descendants) but because they're like those Russian dolls with one inside the other it has resulted in a proliferation of names (for example, modern Neornithine birds belong to the clade Ornithurae, which nests within Ornithothoraces, which belongs to Pygostylia, which is in Aves, which is in Eumaniraptora, in Maniraptora, in Coelurosauria, in Tetanurae, in Neotheropoda, in Theropoda, in Saurischia, in Dinosauria...). It's certainly more precise and accurate for taxonomists, but it results in a confusingly large amount of names for non-specialists.

I love cladistics (as opposed to molecular modeling, but I do appreciate it has uses), but as you say it's easy to get confused and forget you're talking about clades rather than families and orders.

My daughter is still in her "dinosaur phase" and we go through one of several encyclopedias as bedtime reading. We've just worked through the big DK book on prehistoric life and has cladograms at the intro to each chapter. Rather than grouping by period it groups by phylum, so that you don't see pelycosaurs until you're in the mammal/synapsid section towards the end. It's quite up-to-date and birds are included towards the end of the reptile/dinosaur section of the book. I'm already indoctrinating her in birds=dinosaurs to flummox her schoolmates.

 

[Deckerd]

Dinosaurs are extinct. Birds aren't.

 

[All Seeing Eye]

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

 

[PlixTixiplik]

This was sent to my pm box. The poster seemed to want annonimity, so i'll leave the name out. I just felt it added to the discussion.

Since equal time for opposing views seems to be frowned upon by some vocal board members, I thought I'd send you this in PM.

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.

Although he tries to argue that the fuzz is a frill-like fin, it is clearly filamentous downy feathers.

Also, Velociraptor had quill knobs where vaned feathers were attached - further evidence for the theropod ancestry of birds.

As for the other things, it is not surprising that theropods have a mixture of crocodile-like and bird-like characters, as dinosaurs are "intermediate" between those two living groups. Crocodilians and birds are the two types of living archosaur reptiles. I don't think people would argue that dinosaurs were fully bird-like in their metabolism, but there has been a lot of work on bone paleohistology suggesting that they clearly grew rapidly (more like birds, although there are other differences to bird bones too). The uncinate processes I mentioned in an earlier post only occur in derived non-avian theropods and in birds, and articulate the ribs to each other to effectively act as bellows and pump the chest. This indicates that maniraptoran theropods had high oxygen consumption and a bird-like breathing system. Likewise, the absence of nasal turbinates is perhaps not the strongest line of evidence because they do not fossilize well. Nasal turbinates have never been found in fossil birds either (even from the Cenozoic) so their absence from fossil theropods may or may not be indicative of breathing rate.

Given the diversity of dinosaurs and their geological range, it's not surprising to encounter a variety of metabolic strategies (as in mammals - some bats are not homeothermic). And it's likely that theropod metabolism and breathing became more bird-like as they evolved. Relatively basal theropods (like the Coelurosaurians mentioned on the website) probably differ from the more derived bird-like Eumaniraptora. Also, it may not seem like a long time ago, but our understanding of theropod dinosaurs and early birds has really been revolutionized since the articles cited in the website (all from the late 90s), primarily because of the amazingly-preserved specimens from China. Sinosauropteryx in the mid to late 90s was one of the first feathered dinosaurs and was a bit controversial then, but now we know of many feathered dinosaurs so it's not unusual.

-MEC

 

[Aquehonga]

Great thread Kaziarl

What if birds are the “bats” of an extinct class of warm-blooded vertebrates?

That warm-blooded vertebrate class being the extinct “reptiles” called dinosaurs.

Imagine if ALL mammals went extinct except bats?

Then in the far future the the next civilization, of what animal class I can't imagine right now, find fossils of elephants, rhinos, big/small cats, humans/apes, farm animals, dogs, whales, & other mammals & erroneously assume they were reptiles.

These people have always known bats as the flyers of the friendly skies, as well as species of flightless bats in their world, some big ala ostriches, some oceanic ala penguins.

These folks' bats are active both day & night. Not primarily nocturnal as most bats NOW are.

To cut to the chase, one day, after years of study, folks realize those extinct animals (non-bat mammals) are the same class of animals bats are & NOT reptiles at all.

My point is BIRDS are (most probably, definitely,) to the animals we call DINOSAURS what BATS are to all other mammals.

Memo to the over-analytical Herberts obsessed with technicalities:

*The issue of the existence or non-existence of birds in that imaginary Far Future is IRRELEVANT. I was making a point via a metaphor.

So no Professor from “The SIMPSONS” dork geekisms please

Despite my plea, you KNOW the Dweeb Squad(s) are going to, to my agony, prove me right ala long-haired high-fallutin replies

“Oh, the pain!”, as Dr. Zachary Smith would say.

*I know, as does your average cocker spaniel, that pterodactyls/pterosaurs & the ocean reptiles were NOT dinosaurs.

Can hear some pencil-necked geek pointing that out to me already

*Speaking of ptero“saurs” & pterodactyls, I'll be posting a topic about those intriguing fascinating creatures SOON

That's my 3 cents mack!

 

[Neopeius]

My daughter is still in her "dinosaur phase" and we go through one of several encyclopedias as bedtime reading. We've just worked through the big DK book on prehistoric life and has cladograms at the intro to each chapter. Rather than grouping by period it groups by phylum, so that you don't see pelycosaurs until you're in the mammal/synapsid section towards the end. It's quite up-to-date and birds are included towards the end of the reptile/dinosaur section of the book. I'm already indoctrinating her in birds=dinosaurs to flummox her schoolmates.

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

 

[Kaziarl]

Great thread Kaziarl

What if birds are the “bats” of an extinct class of warm-blooded vertebrates?

Now that you bring that up, I did notice that pterodactyls have a wing design closer in style to bats then birds. Bird wings, and I've eaten plenty of fried ones to know where all the bones are, don't have any 'skeletal fingers.' However, ptery's and bats have the equivilent of the upper and lower arm, and then I believe 3 more bones that come off of that like fingers. The skin of the wing is stretched between these fingers while in flight.

Now, this might be wrong, but I'm under the impression that there were two classes of dinosaur. That site that was sent to my pm box makes part of the point. While dinosaurs are physically similar across the board, I think there were certain difference that set them apart. Some had feathers which makes one think they are distant ancestors of birds. Some had batlike wings, and although looked like dinosaurs, maybe were actually early mammels. We do know that things can make large jumps in there form, we for example still have the genetic code for gills, it's just simply turned off. I also think some of them didn't evolve. and that the only 'true dinosaur' so to speak, is that monster of a lizard on the galopagos islands.

 

[PlixTixiplik]

Great thread Kaziarl

What if birds are the “bats” of an extinct class of warm-blooded vertebrates?

Now that you bring that up, I did notice that pterodactyls have a wing design closer in style to bats then birds. Bird wings, and I've eaten plenty of fried ones to know where all the bones are, don't have any 'skeletal fingers.' However, ptery's and bats have the equivilent of the upper and lower arm, and then I believe 3 more bones that come off of that like fingers. The skin of the wing is stretched between these fingers while in flight.

All three groups (birds, bats, and pterosaurs) evolved flight independently so they are excellent examples of convergent evolution. Bats and pterosaurs do have "finger-wings" that differ from bird wings, as you note. But pterosaurs and birds have very similar-looking pectoral girdles (the breastbone/shoulder/collarbone area). They both have large breastbones with a raised keel for muscle attachment. Although pterosaurs don't have a wishbone like birds they instead have a prong that sticks off the top of the breastbone fulfilling a similar function (muscle attachment - it takes a lot of power to fly).

Now, this might be wrong, but I'm under the impression that there were two classes of dinosaur. That site that was sent to my pm box makes part of the point. While dinosaurs are physically similar across the board, I think there were certain difference that set them apart. Some had feathers which makes one think they are distant ancestors of birds. Some had batlike wings, and although looked like dinosaurs, maybe were actually early mammels. We do know that things can make large jumps in there form, we for example still have the genetic code for gills, it's just simply turned off. I also think some of them didn't evolve. and that the only 'true dinosaur' so to speak, is that monster of a lizard on the galopagos islands.

The two major groups of dinosaurs are the Ornithischia ("bird-hipped dinosaurs" like Triceratops, Stegosaurus, and the duck-billed dinos) and Saurischia ("lizard-hipped dinosaurs" like sauropods, theropods, and birds). Yeah, birds belong to the "lizard-hipped dinosaurs" - it's confusing. There is definitely a huge amount of variation there, both in anatomy, lifestyle, and metabolism. Ornithischians and sauropods were probably much more like reptiles, in terms of egg-laying, activity levels, etc.

But the pterosaurs with the bat-like wings aren't dinosaurs (although they were somewhat related to them, belonging to the group Archosauria like crocodiles, dinosaurs, and birds). And they didn't give rise to mammals. In fact, mammals are a very distinct group that diverged from all other land vertebrates well before the time of the dinosaurs. Other than amphibians, everything else (lizards, snakes, reptiles, turtles, birds) belongs to a group called Diapsids, while mammals are Synapsids (the only living synapsids). They differ in the structure of the skull, among other things, and split apart from a common ancestor way back in the Paleozoic (about 320 million years ago). Some modern lizards may look kind-of like dinosaurs, but they actually aren't really that related. Lizards belong to a whole different group of Diapsids - the closest living relatives to dinosaurs are birds (which descended from one particular group of dinosaurs) and crocodiles (which shared a common ancestor with pterosaurs/dinosaurs).

 

[Aquehonga]

Kaziarl, I shouldn't have put that MEMO thingee, ^, but when posting my reply I couldn't help but think of all those tit-for-tat long haired high-fallutin replies aficionados were having back & forth, forth & back, tit-for-tat,yada,yada,yada in other forums within TrekBBS.

Most recent example being that /Dominion thing that was up in GenTrek recently & the unending b&f/f&b/tit-for-tatting aficionados were having about that

I was getting the heebie jeebies replying having visions of aficionados replying to my reply with peer reviewed journals & PhD theses as replies

Which is why I put that aggressive, & obnoxious, memo!

That, thank God hasn't happened

Anyway, what I should've said was:

The oceanic Mesozoic reptiles were NOT dinosaurs & never were or will ever be considered dinosaurs

The ptero"saurs"/pterodactyls haven't been, & to my recent knowledge, still aren't classified as dinosaurs, but are closely related to them

The aficionados I'm thinking of, & its a small minority, like 2-3 TrekBBSers, haven't yet posted their 800,000 word replies to this here topic

Aficionados probably know which aficionados I'm thinking of without casting aspersions. I don't & won't name names as that's being a weasely little ratfink no-goodnik

Well, enough of me morphing into the thing I'm whining about while whining about it

Back to topic!