Archaeopteryx and Dino-Bird Evolution

google, it turns out, is totally useless. anyways, i was searching for something else dinosaur related (sauropods) today, and stumbled across this page:Lecture 19 - Late Jurassic: Solnhofennow, i've been looking at similar pictures in books for my art project, but it's hard to find such clear diagrams on the web. take a look at the archaeopteryx compared to the pigeon (like i did above) and it compared again to dienonychus below. then look at the transitional chart of hands.

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I saw a vision of a raptor jumping up and flapping its arms as it crashed into the ground. I think this is the evolution of flight, which is that of jumping dinosaurs (using their large feathered arms for flapping as they neared the ground). It looks like it has downy though, like baby ducklings, which does make sense because I would think that original mammals had no fur. Similarly, early feather would have been downy.I can see into the past, and I think anyone can. The spirits of the dinosaurs still remain.I am thinking that feathers not only evolved to serve better maneuvering, but also helped dinosaurs survive their extreme activity which may have been jumping up and landing. They could glide to the ground, which would be good for avoiding tough impacts.So, I do believe feathers evolved to help animals while jumping as well as running. Overtime the creatures, as they began to climb trees, probably used the feathers in leaping large distances. It is then a short distance to learning to fly.

And has anyone considered that tyrannosaurus rex's arms were feathered? Why else would that be so small? Perhaps tyrannosaur rex's did have feathers to some degree or fashion.

t. rex's arms were so tiny because it didn't use them. i think of tyrannosaurids as land-sharks: a walking set of jaws. like most sharks, t. rex would probably have eaten whatever it could. its jaws are built for bone-crunching, and its legs are proportioned more and more for endurance walking towards the end of its reign. this indicates, for most, that rex was not a picky eater nor did he survive primarily by actively taking down prey. he would probably get to the prey last, and crunch through the bones to get the bits the smaller and faster hunters could not. arms are more or less useless for this purpose.compare to a velociraptor, who has extremely long grasping arms useful from hunting, and legs proportioned for sprinting.t. rex is not by any means in the dino-to-bird line but recent studies have shown that feathers probably went back much further down the tree than even dromeosaurids and avian dinosaurs, suggesting that even tyrannosaurids probably had some form of feathers. for instance, dilong paradoxus is an early tyrannosaurid that was found to have feathers. so a late tyrannosaurid like t. rex probably would have as well.i kind of picture him looking a little like a vulture. a really big, really ugly vulture.

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Such sexy beasts, aye?

no, probably not. horner suggests that t. rex would have been quite ugly (like the vultures i mentioned) in order to help scare away other predators from their prey.This message has been edited by arachnophilia, 01-18-2006 09:40 PM

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I wouldn't put too much faith in anything Horner says -- especially as it pertains to T. rex. And just to add/clafify to some things said earlier in this thread...- Cladistically speaking, humans are NOT classified as reptiles. We are derived from synapsids (the primitive ones informally known as "mammal-like reptiles"), essentially the sister clade to "reptiles".- Interesting to note that some dinosaurs (oviraptorids, specifically -- Nomingia, more specifically) had pygostyles.- It has been argued numerous times now that dromaeosaurids ("raptors") are, in fact, secondarily flightless birds, due to their being more bird-like than Archaeopteryx in some ways.Just some food for thought.

Hi, new guy!I like your illustrations a lot!

Has anyone mentioned Microraptor yet? That's one of my favorite dino-bird transitional fossils; I often use an artist's rendering of M. gui as my avatar on other forums. Image Source: National Geographic

heh, yeah. he tends to be a little on the screw-ball side about that sort of thing. i think he's a little too staunch of a supporter for the scavenger-only idea of rexy. one could attain a more realistic perspective by comparing t. rex to modern equivalents, like the lion. in some parts of africa, primarily lions do the hunting and hyenas scavenge. in other parts, it's exactly reversed. i suspect that t. rex would probably have occupied both social roles: hunting when it could and scavengening when it could.but i thought the vulture idea was interesting, especially since we're now pretty certain that tyrannosaurids had feathers. well, yes. but the synapsid were reptiles at the time. we run into problems here and there with cladistics, if we only look in modern terms, because there aren't always modern varieties of things. where do we put dinosaurs? are theropod dinosaurs birds, or vice versa? yes, quite. we see various avian features arising all over the place. i was actually thinking of posting a thread about this. now that this thread has generated some more interest, i'll just post it here.i don't know if i would call velociraptor or dienonychus a flightless bird. i'm also not sure how they are "more bird-like than archaeopteryx" either. skeletally, they share the vast majority of their features. the thing that makes archaeopteryx "special" is the feathers. we know it had them, but we don't know if dromeosaurids did (although it's VERY likely).but i'd like to make a suggestion, in line with my "archaeopteryx is not a bird" stance. i'm starting to think that archaeopteryx isn't even remotely special -- just well preserved. there's a gene in modern birds that produces feathers. and there's a gene that takes SOME feathers and modifies them into scutes. we know this, because this is what happens when we turn off that second gene:birds grow feathers on their feet, instead of scutes. scutes are the second type of scale that a bird has. the first is very reptilian, but scutes are genetically and chemically the same as feathers, made of keratin. and that's because they're actually derived from feathers. the issue here is that we know dinosaurs had scutes.the problem is that it's not just the theropod dinosaurs that have scutes, either. anklysaurs had them. which means that the genetic code for feathers existed before the saurischia/ornithischia divide. so the only dinosaurs that didn't have feathers are the ones that lost them, due to size or further adaptation. this also explains microraptor (above) quite nicely. it had the genetic code for feathers on its feet (like modern birds) but lacked or contained defective copy of the code to turn those feathers into scutes.but this puts feathers WAY before birds: they are no longer a feature that we can use to classify something as a bird. i'd like to further suggest that their origin would be around the time the first warm-blooded animals were evolving. since one of the primary functions seems to regulation of body temperature, this would make sense. the first dinosaurs we see are essentially small bipedal animals -- pushed away from the ground because they no longer require proximity to it for warmth. the large quadrupedal dinosaurs like stegosaurs and sauropods and the like all have early bipedal ancestors.feathers therefore might be a better indicator that something is a dinosaur, though as i said we should expect to see feathers evolving BEFORE the dinosaurs in other reptiles like longisquama. longisquama is a curious reptile (archosaur? ... ?) that appears to have feathers:we also know that pterosaurs had something like hair, which may mean that their ancestors had a step in the evolution of feathers as well, only used for warmth instead of flight.so the next question is: what is a bird? skeletally, archaeopteryx and dromeosaurids aren't really all that that special either. they have back-turned hips, sure. but they're only slightly like even the earliest bird hip we have from the cretaceous. they have semi-lunate carpals and wishbones, which are great for flight, but no keeled breastbone for the flight muscles to attach to. neither has a reversed hallux, and both have fully formed theropod hands. although the bones are highly pneumaticized, they're not fused together in the right ways in the arms or legs.archaeopteryx and other theropods represent a class of highly avian dinosaurs that share many (but not all) features with birds. they seem to be somewhat closely related to ancestors of modern birds, and are thus good indicators of how birds evolved. but i wouldn't call them birds quite yet. there are just too many differences in my eyes.

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well, yes. but the synapsid were reptiles at the time.

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They were 'reptiles' under traditional Linnaean classification, which went out of style twenty years ago. The more highly derived "pelycosaurs" were already quite different from other typical reptiles.

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where do we put dinosaurs? are theropod dinosaurs birds, or vice versa?

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Birds are definitely theropod dinosaurs, but not all theropod dinosaurs are birds.

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i don't know if i would call velociraptor or dienonychus a flightless bird. i'm also not sure how they are "more bird-like than archaeopteryx" either.

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For one thing, Velociraptor has uncinate processes -- a very birdlike feature (though seen in other reptiles as well). Other aspects of the pectoral girdle suggest bird affinities as well. Read any of Greg Paul's two books to learn more. He's the one pushing hardest on this front lately.

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the problem is that it's not just the theropod dinosaurs that have scutes, either. anklysaurs had them. which means that the genetic code for feathers existed before the saurischia/ornithischia divide.

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I really don't think that bird 'scutes' (i.e. scutellate tarsi) are at all homologous to the bony scutes in ankylosaur skin, so I don't know how far that argument will get you.

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longisquama is a curious reptile (archosaur? ... ?) that appears to have feathers

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I think you'll have a hard time arguing that those structures on Longisquama are real feathers if you look at them in detail. Some have even suggested they're just preserved fern fronds.

quite -- i just don't think we can go dashing off calling all theropods "birds" willy-nilly. right, but that doesn't make it a bird. there are a lot of skeletal similarities, but as you point out many are shared by other reptiles, and very many by other theropods. and very few of those features are exactly the features of things that are definitively birds, just analogous, transitional features still much more similar to classical dinosaurian features.i'm just arguing that birds are highly modified theropodal dinosaurs, but like you said, not all theropods are birds. the primary feature i look for in calling something "bird" is the clawless, fused digits of a bird wing. a "true" wing, as opposed to an arm and hand with flight-feathers like archaeopteryx. it doesn't even neccessarily have to be used for flight, just present in some form. modern flightless birds have wings, because their ancestors flew. the cretaceous "backwards/opposite birds" have wings as well, even if they were an evolutionary dead end. well, it was just a suggestion. i think it warrants looking into. some have, yes. personally, i don't know. i looked for a few nights on various paleontology sites and fora, and couldn't find a definitive answer, just a LOT of debate. i found one high-resolution photo of the "feathers" on the internet, but it's way too blurry and grainy to look at any detail. it's obvious that there's a central vein and somewhat tightly arranged somethings coming off of it. if it's a ferm, it's kind of a strange arrangement (and size? can't tell) for a fern. but if it's a feather, it's still kind of strange.but an extremely early evolution of feathers would be a good explanation for longisquama. and it fits in pretty close to the evolution of the earliest forms of warm blooded animals. i suspect that hair, feathers, and any other skin-coverings of keratin like beaks all share their basic developmental stage around this time. but i don't know. it's just a thought.

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quite -- i just don't think we can go dashing off calling all theropods "birds" willy-nilly.

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I completely agree. But I don't know of anyone who is refering to some theropods as flightless birds without good reason. Note that I don't necessarily subscribe to this idea; just playing devil's advocate.

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the primary feature i look for in calling something "bird" is the clawless, fused digits of a bird wing.

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Very well. That's still very much a subjective choice, as I'm sure you will agree. Other scientists might chose another apomorphy by which to identify birds. Still others would rather describe birds based on their relationships to other groups (i.e. stem- or node-based definitions).

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but if it's a feather, it's still kind of strange.

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There has certain been much literature on the issue. For the pros, see:
Jones, T.D., J.A. Ruben, L.D. Martin, E.N. Kurochkin, A. Feduccia, P.F.A. Maderson, W.J. Hillenius, N.R. Geist, and V. Alifanov. 2000.
Nonavian feathers in a Late Triassic archosaur. Science 288: 2202-5.
The cons:
R.R. Reisz, H.-D. Sues. The "feathers" of Longisquama. Nature 408:428.
As far as I'm concerned, even if the 'feathers' of Longisquama and birds were one and the same (which I don't think they are), the rest of the skeleton just doesn't compare at all between the two. Longisquama definitely isn't a contender, at least as far as bird ancestry is concerned (which I know isn't what you're contending, arachnophilia).

i picture dinosauria as a whole precariously perched between the ancient ancestors of crocodiles and modern birds. even the most un-bird-like dinosaurs share many birdlike features: upright posture, hips, hollowed bones, probably warm blood, etc. it's romantic to think of velociraptor like a big bird -- and it's a good comparison. it would be very much like flightless predatory bird. i'm willing to bet that it even had wings (in terms of feathers).but it's not a bird. and it's not a crocodile. it's somewhere in the middle. yes, it's quite a tough question of where we draw the line. what is a bird? what's a dinosaur?i'm currently giving two books a read. i picked up "the dinosaur heresies" by bakker, and "predatory dinosaurs of the world" by gregory paul at the used bookstore today. as it stands, i think i will still contend that birds and dromeosaurids share a common ancestor, but are not closely related enough to put in the same clasification as "birds." the dromeosaurid line did not produce modern birds, if memory serves.edit: it appears dr. bakker actually wrote something on longisquama. i'll see if i can find that paper, too:

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Also Bakker (1975: p. 68) stated that the scales of Longisquama constituted a structural stage in the evolution of feathers.

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Bakker, R.T. 1975. Dinosaur renaissance. Scientific American 232, 58-78.
http://app.pan.pl/longisquama.htm

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it'd be great to have his input here, though since he only posted once, i doubt he'll be back. i'm frankly just amazed that even posted here at all.../edit from what i've heard, feduccia's theories are not well regarded in the paleontology community. i've heard some even claim that he is intellectually dishonest, or that he is ignorant of dinosaurian biology and anatomy.he alleges that birds evolved from other thecodonts, not theropod dinosaurs, and that the dromeosaurid likeness is just convergant evolution. that's a little bit extreme -- i doubt they are that distantly related, though i do think he may have a point about bird-like tendencies evolving fairly early. there is even the odd bird-like feature in crocodiles, but not enough to establish any close relationship. the similarities are veen more present in dinosaurs, and most present in theropods like dromeosaurs. unfortunately, i can't get the article at just this second -- i'll have to take a trip to library, unless you can post some pertinant quotes. i'm kind of interested in what people more knowledgeable than i are actually saying about this "feathered" lizard. no, it doesn't at all, does it? actually, it's skeleton (the parts we have) are fairly confusing as it is:it's hard to tell from the illustrations what's really going on -- i'm not very qualified to make any kind of good scholarly opinion here -- but it appears to have clavicles, long (mobile?) shoulder blades, and the start of some kind of breastbone. now, chameleons have similar shoulder blades, and i think breast-bones. but it's clavicles aren't very lizard-like.Jaime Headden reconstructs longisquama like a theropod:
This website is frozen.which, imo, is probably very wrong. it doesn't really look like a dinosaur to me. actually, it looks more like a pterosaur. it's not, but it has some similarities. the hand/wrist structure in particular, and the skull. dinodata says:

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In Peters, D., 2000. "A reexamination of four prolacertiforms with implications for pterosaur systematics," Rivista Italiana di Paleontologia e Stratigrafia 106(3): 293-336 [December 2000] the describer supersedes all previous work on Longisquama, Cosesaurus, and Sharovipteryx and places them well inside the Prolacertiformes. In particular, this removes Longisquama from Dinosauria.

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Longisquama insignis known primarily from a crushed fossil preserving only the fore parts of the animal, and also a number of disassociated "long scales." was found in 1969 in Kyrgyzstan by the Russian insect paleontologist A.G. Sharov. The skull appears to have diapsid openings.

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Dinodata.net - Refinansiering av gjeld og ln

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in short, i don't really know what it is. but it's not a dinosaur, which means it's not a theropod, which means it's not a bird. it seems to be a member of archosauromorpha, but not an archosaur. no, absolutely not. i was using it as an indication that (if those ARE feathers then) some of the particular peculiar features we assign to dinosaurs and birds may not be so new, and that feathers may actually have existed prior to dinosaurs in some primitive form. if i recall, feduccia contends that longisquama and some other ridiculous lizard are the "true" ancestors of birds. which, i think, is laughable at best.This message has been edited by arachnophilia, 02-21-2006 01:36 AMThis message has been edited by AdminJar, 02-21-2006 10:48 AM

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as it stands, i think i will still contend that birds and dromeosaurids share a common ancestor, but are not closely related enough to put in the same clasification as "birds." the dromeosaurid line did not produce modern birds, if memory serves.

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You're right in saying the dromaeosaurid line did not produce birds. It is commonly argued that the deinonychosaurs (dromaeosaurids + troodontids) are the sister taxon to the birds.
But maybe after reading Paul's book, you will change your mind. That book is terribly out of date, mind you. I'm just impressed that you were able to pick up PDW at a used book store -- that thing is very hard to come by.

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from what i've heard, feduccia's theories are not well regarded in the paleontology community. i've heard some even claim that he is intellectually dishonest, or that he is ignorant of dinosaurian biology and anatomy.

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Is it any wonder creationists continually cite him for support?

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he alleges that birds evolved from other thecodonts, not theropod dinosaurs, and that the dromeosaurid likeness is just convergant evolution.

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I think he has even changed his tune now and argues that neither birds NOR deinonychosaurs are theropods, but evolved instead from a drepanosaurid-like ancestor. There was a paper on this recently...

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unfortunately, i can't get the article at just this second

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If memory serves me, the Reisz paper is available on his lab website for download.