Flight evolved twice?

According to this BBC article they've made some new finds that appear to indicate flight evolved twice.This is more a request for more information, than anything else, does anyone have more details?Mods, stick it wherever you think it goes.

Thread moved here from the Proposed New Topics forum.

Interesting.On a slightly related note, some people think that flight arose twice in the bats as well; microchiroptera and megachiroptera may be independent lineages from a non-flying common ancestor.

Since so many other things seem to have evolved multiple times, locomotion, sight; it would not be surprising if flight evolved multiple times.

---

Aslan is not a Tame Lion

Flight evolved lots of times. Birds, bats (maybe twice there), reptiles, and insects.

---

No smoking signs by gas stations. No religion in the public square. The government should keep us from being engulfed in flames on earth, and that is pretty much it. -- Jon Stewart, The Daily Show

Not to mention that terrestrial tetrapods have returned to the ocean at least twice (icthyosuars and whales), and seals may be yet another on that path.edited to add:Almost forgot penguins, who also may be on that path as well.This message has been edited by Chiroptera, 13-Oct-2005 03:58 PM

---

"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

i think that's a little sensationalized. everytime they find a raptor nowadays, they bill it as revolutionizing bird evolution. in reality, it's been knows that flight characteristics, especially feathers, developed over a wide range of dinosaurs. it's not that it evolved "twice." it really only evolved once, just not through any specific animal. it seems to have been the general trend of theropod dinosaurs.heck, we've even found a tyrannosaurid with feathers, which suggests that feathers go back as far ceolurosaurid/tetanurae/dromeosaurid divide -- ie: feathers came about before this guy's grandpa was around.looking at the article, i see some mistakes, too.compare this picture: to this picture: they changed the head. the picture and the article give the impression of something similar to a beak -- a long slender snout. the slender bit they're referring to is the standard dromeosaurid skull. dromeosaurus itself has an identical looking skull -- blocky from the side. it does not terminate in a point.it's limbs are also NOT "wing-like." they are arms, with fingers, not the fused digits of a wing. it has very proportionatly long arms, maybe a bit longer than other dromeosaurids.in regards to bird like qualities, i see nothing special in this one. it seems to be missing half of the hip and the sternum, which i could tell a lot from. i also can't seem to tell if the clavicles are fused or not. but the hallux is not bird-like.if it had feathers, i wouldn't be suprised, but the article doesn't say. what it DOES suggest is that the dromeosaurid common ancestor is further back than previously thought. and what they mean "flight evolved twice" is that they think it evolved in south america indepently from china/us. so, "yay for convergent evolution among really similiar species." no suprise here, really.in reality, theropod dinosaurs were not the only archosaurs to grow wings and fly. pterosaurs did long before birds were around. and more recently, so did bats. so if we wanna be technical here, flight evolved THREE times in archosaur descendants.

---

אָרַח

quote:

---

in reality, theropod dinosaurs were not the only archosaurs to grow wings and fly. pterosaurs did long before birds were around. and more recently, so did bats. so if we wanna be technical here, flight evolved THREE times in archosaur descendants.

---

Careful. One could read this paragraph and conclude that you consider bats to be descendants of archosaurs.

---

"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

all modern reptiles, all mammals, all dinosaurs, and all birds came from archosaurs, yes.mammals, if i recal, came from therapsid pelycosaur archosaurs, crocodiles, dinosaurs (birds) and most modern reptiles seem to have come through diapsid thecodont archosaurs. but i'm not terribly clear on pennsylvanian evolution.

---

אָרַח

Archosaurs are the crown clade of modern birds and modern crocodiles (and, so therefore include dinosaurs as well). That is, the closest modern relatives of dinosaurs (other than birds) are the crocodiles and alligators -- these are classed together as Archosaurs. And actually, this common ancestor also include the pterosaurs, so pterosaurs are also Archosaurs.There may be other meanings to the word, but this is the only one that I am familiar with.

---

"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

If any of you want to read the Nature article, email me....

err, i'm sorry, i must have been mistaken. like i said, not to clear on pre-dinosaurian evolution. i think i was just using the term wrong.anyways, not the only amniotes...

---

אָרַח

You could say that at least three lineages that arose out of the reptiles developed flight (if you consider the ancestors of mammals of reptiles, which I, a non-biologist, do not ).

---

"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

yes, that's sort of what i was going for. we all make mistakes -- i got you back in the other thread This message has been edited by arachnophilia, 10-13-2005 03:28 PM

---

אָרַח

Heh. I saw it. Classification seems to make asses monkeys of us all.This message has been edited by Chiroptera, 13-Oct-2005 07:41 PM

---

"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt