Has it been pretty much proven that birds are descended from dinosaurs? Or is there still some debate about this among paleontologists?
Any info would be appreciated!
Precise details are up for dispute. But it’s one of the triumphs of the cladistic approach that it can be demonstrated what primitive birds have in common with a specific small group of dinosaurs, by a sequence of dichotomous splits narrowing down groups with common characteristics. Perhaps Colibri, or Darwins Finch if he’s still around, can link to the precise cladogram.
There are still small debates going on over small points, but in general it is considered no longer controversial that dinosaurs evolved into birds. Many dinosaur fossils even show signs of having protofeathers and later barbed feathers. However, some people are still fighting the idea.
from the wikipedia page
brackets mine
I just saw on the Discovery Channel a show talking about the anniversary of Darwin and it has been found that Velociraptors had feathers. Something pretty interesting I thought.
Yeah, I’m still around.
The mainstream scientific consensus is that, yes, dinosaurs evolved from birds. Here is a .pdf showing the latest “supertree” of dinosaurian relationships. Note the presence of “Aves”, tucked away next to Troodon, deep within the Therapoda (the bipedal, “meat-eating” dinosaurs like Tyrannosaurus and Allosaurus). The article which explains the tree is here.
The single biggest obstacle to deriving birds from dinosaurs (for the holdouts) is the numbering of avian digits vs. dinosaurian digits. Birds possess digits 1,2 & 3 (think “thumb”,“index finger”, “middle finger”) in their “hands”, while theropod dinosaurs have traditionally been considered to have digits 2,3 and 4 (with 4 being lost in the Tyrannosaurids, leaving them with two-fingered hands). See here for a brief summary and explanation, as well as a possible “workaround”. But see also this paper (another .pdf doc).
Aside from that particular issue, that birds evolved from dinosaurs is supported by pretty much all morphological studies (both in terms of bones morphology and articulations, and feathers), and numerous functional studies as well, which discuss the evolution of such avian characteristics of the flight stroke and their particular modes of terrestrial locomotion. Everything also happens to line up nicely in the fossil record as far as timing goes. So, there’s pretty much a ton of evidence in the “for” column these days, and some questions that require further research, but not much to be found that can be decisively placed in the “against” column.
Indeed, that is also becoming more mainstream. See, for example, the illustrations for Velociraptor on Wikipedia (not that that’s supposed to prove anything, of course; just to note that the “feathered dromaeosaur” is also largely the consensus in paleontological circles these days. See also the article on Deinonychus). The exact amount and location of the feathers is still rather speculative, but it’s become clear that feathers evolved much earlier than actual flight did.
Clearly the dinosaurs also had a TARDIS.
Well. Just goes to show how addled my brain is right now. I meant “into”, not “from”. Or “birds” instead of “dinosaurs” followed by “dinosaurs” instead of “birds”. Whichever way makes more sense.
Just to add that some of the most convincing visible evidence seems to be all the new feathered dinosaur fossils coming out of China these days.
As far as I’ve read, birds descending from dinosaurs is uncontroversial and taken pretty much for granted. Birds actually being dinosaurs (or a subgroup thereof, or the distinction being only a common usage issue) is what cutting-edge cladisitics now argues. Basically, not all the dinosaurs went extinct. Some of them are outside my office right now, on the building ledge, eyeing me.
edges away from window
While some of the more hardcore Linneaen taxonomists might not care for the whole “birds are dinosaurs” idea, it’s really no more controversial than humans actually being mammals. Cladistics is a 50-year old methodology by now, and is pretty much the norm for phylogenetic studies these days. Really, the only folks who haven’t accepted the idea are a) the general public (who are collectively slow to accept any new idea), and b) those folks who don’t agree that birds are even descended from dinosaurs.
Again, though, amongst paleontologists and most ornithologists, there isn’t much debate to be had.
That’s the more controversial part, but there we’re just talking about naming conventions. If you need to use the term Dinosaur (which is now a Superorder, whatever the hell that is), and if you need to include the two early and classic Dinosaurs Megalosaurus and Iguanodon, becuase that’s what Richard Owne did back in 1842, then yes, Aves is part of Dinosauria. They apparently had a common ancestor but exactly when Aves split off is still not entirely known.
But face it Owen didn’t really know what he was talking about and he lumped Ornithopods and Saurischia together. They really are quite distinct. But he found two huge extinct “reptiles” and they had a number of common features so he came up with Dinosaur.
Lumping Aves in with Dinosauria is clumsy, leading to this sort of thing from wiki *“From the point of view of cladistics, birds are dinosaurs, but in ordinary speech the word “dinosaur” does not include birds. Additionally, referring to dinosaurs that are not birds as “non-avian dinosaurs” is cumbersome. For clarity, this article will use “dinosaur” as a synonym for “non-avian dinosaur”. *” and "Using one of the above definitions, dinosaurs (aside from birds) can be generally described as terrestrial archosaurian reptiles with limbs held erect beneath the body, that existed from the Late Triassic (first appearing in the Carnian faunal stage) to the Late Cretaceous (going extinct at the end of the Maastrichtian).[9] Many prehistoric animals are popularly conceived of as dinosaurs, such as ichthyosaurs, mosasaurs, plesiosaurs, pterosaurs, and Dimetrodon, but are not classified scientifically as dinosaurs. Marine reptiles like ichthyosaurs, mosasaurs, and plesiosaurs were neither terrestrial nor archosaurs; pterosaurs were archosaurs but not terrestrial; and Dimetrodon was a Permian animal more closely related to mammals."
Personally, I think we should not try and lump Ornithopods and Saurischia together. We should use the term Dinosauria to refer to any of a large number of large retile-like extinct creatures, including Ornithopods, Saurischia, ichthyosaurs, mosasaurs, plesiosaurs, and pterosaurs, exactly as the public now percieves the term.
The problem with DrDeth’s “common usage” is that biology doesn’t follow common sense. mammals give birth to live offspring, instead of laying eggs – except for the platypus and echidnas. Do you write a definition for ‘mammal’ that excludes them, or figure out how to incorporate them. Everybody realizes what unites the waterfowl – ducks, geese, and swans – but biologically the screamers are in the same group, despite morphological dissimilarities.
When I was growing up, ‘dinosaur’ was like ‘ungulate’ – an imprecise term that united two strongly distinct groups on the basis of a couple of common characters. But studies in the last 30 years have demonstrated that Dinosauria is a single group, a clade in cladistic parlance, that early diverged into saurischians and ornithischians – and that some smaller saurischians developed avian characteristics – in short, became the first birds. So either birds are the surviving group of dinosaurs, or you have a classification that omits the surviving, most successful branch of the family (‘family’ in everday parlance, not the specialized taxonomic meaning).
Most of humanity today has gone through life without seeing, in the flesh, any perissodactyl not a member of genus Equus – horses and ponies, donkeys and asses, mules, and possibly a zebra in a zoo. This does not, however, mean that the idea that rhinos, tapirs, and all their extinct relatives are not the closest relatives of the equids.
The closest living relative of a coelacanth (other than another coelacanth) is a tetrapod. Sometimes folk taxonomy is not accurate. “Dinosaur = big extinct reptile” is one of those times.
Nova had a fascinating show on last night titled “Four Winged Dinosaur” or something to that effect. A “microraptor” in China displays some prominent raptor/therapod traits, but also had fossilized feathers on all four limbs. The feathers were aerodynamically shaped and suitable for gliding and the rest of the critter seemed more arborial.
Part of the controversy in the show was on how to construct the skeleton, and on whether it pointed to pre-dinosaur ancestors of birds. The supporters of that position seemed to have pretty weak grounds for it.
Are you an endangered species? Should we be concerned?
Hey, thanks for all the info! I love this message board!
The funny thing is, way back in the 1970s, when I was in junior high and high school, I was known as the “Dinosaur Whiz kid” who knew everything about dinosaurs and prehistoric life. I stopped following up on all the latest discoveries when I got to college, however. So much has changed in the intervening years, what with all the exciting new discoveries and theories that crop up with each additional piece of fossil evidence. It also doesn’t help that my brain has turned to mush, and my memory is basically kaput!
I think my next question will be about whale evolution, so stay tuned!
Just to clear up this point, Velociraptor feathers have been proved via direct evidence, not educated speculation based on relationships. At least one specimen preserves evidence of quill knobs on the forelimb exactly like those of modern birds, where ligaments anchoring substantial flight feathers attach to the bone. So not only did they have feathers, they had full-on wings, though probably not big enough to fly with.
Missed the edit window, but forgot the link for the Velociraptor feathers thing…
Because of this, it is speculated by some that Velociraptors and some others may have been descended from flying forms and subsequently lost flight, as modern ostriches have.
Some also believe that Archaeopteryx, the primal ¨bird¨ fossil, shows a Velociraptor-like reflexed claw.
So dinosaurs really did taste like chicken? Or should I say, chicken tastes like dinosaur? 
This is very interesting. I now can’t look at city pigeons without thinking, “Look at the little dinosaur!”