Skip to comments.Pristine Skeletons Shed Light on Early Dinosaur Evolution
Posted on 12/16/2009 9:05:33 AM PST by null and void
Pristine Skeletons Shed Light on Early Dinosaur Evolution
|A reconstruction of the newly discovered Triassic, carnivorous dinosaur, Tawa hallae. Courtesy of Jorge Gonzalez|
When Darwin's finches diverged from their common ancestor, the isolation of their island home allowed many species to arise from one. When their dinosaur ancestors emerged in the Triassic, the island home was the unified landmass Pangea, and the evolution was far more complicated.
In the December 11, 2009, issue of Science, a team of paleontologists introduced the Triassic dinosaur Tawa hallae, an animal that may answer longstanding questions about the earliest years of dinosaur evolution. The Tawa fossils, collected along with other specimens during recent field excursions to Ghost Ranch in New Mexico, are some of the most complete and best preserved dinosaur skeletons from the Late-Triassic time period.
Tawa possesses features that appear in its contemporaries and features that do not, a finding that helps unite all Triassic carnivorous dinosaurs into one group, the theropods, the same group that included Tyrannosaurus rex, and now includes birds. The recent finds also support the hypothesis that dinosaurs first originated in what is now South America and soon after diverged into theropods, sauropodomorphs (the line that includes the ground-shaking giants like Apatosaurus) and ornithischians (a line that includes a range of body types, including Stegosaurus and Triceratops). Only after this divergence did dinosaurs disperse across the Triassic world more than 220 million years ago.
|Based on an analysis of how Tawa relates to other early dinosaurs, researchers hypothesize that dinosaurs originated in what is now South America, and soon after diverged into ornithischians (like Triceratops), sauropodomorphs (like Apatosaurus) and theropods (like Tyrannosaurus rex), before dispersing across the Triassic world more than 220 million years ago. The theropods evolved into modern-day birds, although Tawa split off from the ancestral branch early on and was not a direct bird ancestor. Courtesy of Zina Deretsky, National Science Foundation||
"Tawa gives us an unprecedented window into early dinosaur evolution, solidifying the relationships of early dinosaurs, revealing how they spread across the globe, and providing new insights into the evolution of their characteristics," says Sterling Nesbitt of the University of Texas at Austin, the lead author on the paper.
"If you have continents splitting apart, you get isolation," says Nesbitt. "So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related, endemic radiation," similar to what occurred with Darwin's finches. "But that is what we don't see in early dinosaur evolution," adds Nesbitt.
Instead, Nesbitt and his colleagues observed three distantly related carnivores in the fossil-rich, Late Triassic beds, implying that each carnivore descended from a separate lineage before arriving in North America, instead of all evolving from a local ancestor. In addition to Tawa, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America.
The two- to four-meter-long skeletons of Tawa display characteristics that exist in both of its contemporaries, and features found in neither, implying a separate lineage. Unlike many theropods, Tawa's lineage does not lead directly to birds.
According to Nesbitt, the old view held that Herrerasaurus split off of the family tree after the ornithischians, but before the sauropods and theropods diverged. "Tawa now appears to show that the three groups split from each other as soon as dinosaurs evolved," he adds, though paleontologists have not yet found a concrete example of a dinosaur that existed before the divergence.
"Tawa is a very good example of a fossil that fills in what we call a morphological gap," says Nesbitt, referring to a gap in knowledge about how morphology, or body structures, changed over time, a result of the incomplete nature of the fossil record. While theropods were changing quickly in the Triassic, paleontologists have found few animals that preserve the "steps" that define the sequence of changes.
|A reconstruction of the Tawa hallae skeleton. Courtesy of Sterling Nesbitt|
One of the most significant morphological gaps for early dinosaurs lies between Herrerasaurus and animals that are clearly more closely related to birds, such as Coelophysis. According to Nesbitt, Tawa fits perfectly in between. "It is not a missing link," he adds, "It evolved on its own lineage, but it retains characteristics that existed in Herrerasaurus that we thought were more primitive while also possessing features seen in unmistakable theropods, including birds, such as the presence of air sacs surrounding the braincase and neck."
"Usually, early dinosaur specimens are not as complete or well preserved, so they spur a lot more questions than answers," says Nesbitt. "Tawa is so well preserved that every bone we have, we can examine it in three dimensions. And we can analyze five of the skeletons this way, with examples of both mature and immature animals. This is just the tip of the iceberg. All dinosaurs share a common feature, an open hip socket, and you can dissect your Thanksgiving turkey and still see that original feature. But the earliest lineages that lie in between are far from understood."
|A reconstruction of the head of Tawa hallae. Courtesy of Jorge Gonzalez|
Nesbitt's co-authors included Nathan Smith of the University of Chicago and the Field Museum of Natural History; Randall Irmis of the Utah Museum of Natural History, University of Utah; Alan Turner of Stony Brook University; Alex Downs of the Ruth Hall Museum of Paleontology in Abiquiu, N.M.; and Mark Norell of the American Museum of Natural History, where Nesbitt was a researcher at the time of the discovery.
The research was supported by the National Science Foundation (NSF) through grants to Mark Norell (0228607), Alan Turner (0608003), Nathan Smith (0808250) and NSF Graduate Research Fellowships to Sterling Nesbitt and Randall Irmis. The research was also featured in the NSF-funded IMAX 3D movie "Dinosaurs Alive!" (itself supported by NSF grant 0337269).
The research was also sponsored by the National Geographic Society with other participating institutions including the University of Chicago, the Field Museum of Natural History, the Utah Museum of Natural History, the University of Utah, Stony Brook University and the Ruth Hall Museum of Paleontology.
Bump while I go get some popcorn for this...
This is just inference and conjecture. Need to demonstrate macro-evolution by repeatable means.
In other words, they looked just like...dinosaurs??
Nothing to see indeed. When Darwins Finches were isolated on their islands, what Darwin discovered was a population of......(you guessed it) Finches. Not feathered butterflies, wingless finches, penguin-like finches. Nope. Finches
These fossils are obviously faked, or are 3000 years old, or something.
They remained then as they do now, finches. (Just agreeing with you.)
I’m so confused. In that purported seething cauldron of evolving new species of finches, why doesn’t interbreeding between the nascent “new” species and their “parent” group tend strongly to keep the finch population pretty much homogenized, undergoing random changes, perhaps, but not becoming separate, essentially true breeding, morphologically differentiable species?
Because each nascent species was isolated on its own island, each island had different conditions.
If you had any actual familiarity with Darwin’s work, you’d know that.
I bet you even think that Darwin didn’t credit the Creator with having originally breathed life into a few forms or into one.
The problem is with the basic laws of mathematics and probability, with which evolution is essentially incompatible.
The best illustration of how stupid evolutionism really is involves trying to become some totally new animal with new organs, a new basic plan for existence, and new requirements for integration between both old and new organs.
Take flying birds for example; suppose you aren't one, and you want to become one. You'll need a baker's dozen highly specialized systems, including wings, flight feathers, a specialized light bone structure, specialized flow-through design heart and lungs, specialized tail, specialized general balance parameters etc.
For starters, every one of these things would be antifunctional until the day on which the whole thing came together, so that the chances of evolving any of these things by any process resembling evolution (mutations plus selection) would amount to an infinitessimal, i.e. one divided by some gigantic number.
In probability theory, to compute the probability of two things happening at once, you multiply the probabilities together. That says that the likelihood of all these things ever happening at once (which is what you'd need), best case, is ten or twelve such infinitessimals multiplied together, i.e. a tenth or twelth-order infinitessimal. The whole history of the universe isn't long enough for that to happen once.
All of that was the best case. For the pieces of being a flying bird to evolve piecemeal would be much harder. In real life, natural selection could not plausibly select for hoped-for functionality, which is what would be required in order to evolve flight feathers on something which could not fly apriori. In real life, all you'd ever get would some sort of a random walk around some starting point, rather than the unidircetional march towards a future requirement which evolution requires.
And the real killer, i.e. the thing which simply kills evolutionism dead, is the following consideration: In real life, assuming you were to somehow miraculously evolve the first feature you'd need to become a flying bird, then by the time another 10,000 generations rolled around and you evolved the second such reature, the first, having been disfunctional/antifunctional all the while, would have DE-EVOLVED and either disappeared altogether or become vestigial.
Now, it would be miraculous if, given all the above, some new kind of complex creature with new organs and a new basic plan for life had ever evolved ONCE.
Evolutionism, however (the Theory of Evolution) requires that this has happened countless billions of times, i.e. an essentially infinite number of absolutely zero probability events.
And, if you were starting to think that nothing could possibly be any stupider than believing in evolution despite all of the above (i.e. that the basic stupidity of evolutionism starting from 1980 or thereabouts could not possibly be improved upon), think again. Because there is zero evidence in the fossil record to support any sort of a theory involving macroevolution, and because the original conceptions of evolution are flatly refuted by developments in population genetics since the 1950's, the latest incarnation of this theory, Steve Gould and Niles Eldredge's "Punctuated Equilibrium or punc-eek" attempts to claim that these wholesale violations of probabilistic laws all occurred so suddenly as to never leave evidence in the fossil record, and that they all occurred amongst tiny groups of animals living in "peripheral" areas. That says that some velocirapter who wanted to be a bird got together with fifty of his friends and said:
Guys, we need flight feathers, and wings, and specialized bones, hearts, lungs, and tails, and we need em NOW; not two years from now. Everybody ready, all together now:
You could devise a new religion by taking the single stupidest doctrine from each of the existing religions, and it would not be as stupid as THAT.
But it gets even stupider.
Again, the original Darwinian vision of gradualistic evolution is flatly refuted by the fossil record (Darwinian evolution demanded that the vast bulk of ALL fossils be intermediates) and by the findings of population genetics, particularly the Haldane dilemma and the impossible time requirements for spreading genetic changes through any sizeable herd of animals.
Consider what Gould and other punk-eekers are saying. Punc-eek amounts to a claim that all meaningful evolutionary change takes place in peripheral areas, amongst tiny groups of animals which develop some genetic advantage, and then move out and overwhelm, outcompete, and replace the larger herds. They are claiming that this eliminates the need to spread genetic change through any sizeable herd of animals and, at the same time, is why we never find intermediate fossils (since there are never enough of these CHANGELINGS to leave fossil evidence).
Obvious problems with punctuated equilibria include, minimally:
1. It is a pure pseudoscience seeking to explain and actually be proved by a lack of evidence rather than by evidence (all the missing intermediate fossils). Similarly, Cotton Mather claimed that the fact that nobody had ever seen or heard a witch was proof they were there (if you could SEE them, they wouldn't BE witches...) This kind of logic is less inhibiting than the logic they used to teach in American schools.
2. PE amounts to a claim that inbreeding is the most major source of genetic advancement in the world. Apparently Steve Gould never saw Deliverance...
3. PE requires these tiny peripheral groups to conquer vastly larger groups of animals millions if not billions of times, which is like requiring Custer to win at the little Big Horn every day, for millions of years.
4. PE requires an eternal victory of animals specifically adapted to localized and parochial conditions over animals which are globally adapted, which never happens in real life.
5. For any number of reasons, you need a minimal population of any animal to be viable. This is before the tiny group even gets started in overwhelming the vast herds. A number of American species such as the heath hen became non-viable when their numbers were reduced to a few thousand; at that point, any stroke of bad luck at all, a hard winter, a skewed sex ratio in one generation, a disease of some sort, and it's all over. The heath hen was fine as long as it was spread out over the East coast of the U.S. The point at which it got penned into one of these "peripheral" areas which Gould and Eldredge see as the salvation for evolutionism, it was all over.
The sort of things noted in items 3 and 5 are generally referred to as the "gambler's problem", in this case, the problem facing the tiny group of "peripheral" animals being similar to that facing a gambler trying to beat the house in blackjack or roulette; the house could lose many hands of cards or rolls of the dice without flinching, and the globally-adapted species spread out over a continent could withstand just about anything short of a continental-scale catastrophe without going extinct, while two or three bad rolls of the dice will bankrupt the gambler, and any combination of two or three strokes of bad luck will wipe out the "peripheral" species. Gould's basic method of handling this problem is to ignore it.
And there's one other thing which should be obvious to anybody attempting to read through Gould and Eldridge's BS:
They are claiming that at certain times, amongst tiny groups of animals living in peripheral areas, a "speciation event(TM)" happens, and THEN the rest of it takes place. In other words, they are saying:
ASSUMING that Abracadabra-Shazaam(TM) happens, then the rest of the business proceeds as we have described in our scholarly discourse above!
Again, Gould and Eldridge require that the Abracadabra-Shazaam(TM) happen not just once, but countless billions of times, i.e. at least once for every kind of complex creature which has ever walked the Earth. They do not specify whether this amounts to the same Abracadabra-Shazaam each time, or a different kind of Abracadabra-Shazaam for each creature.
Take flying birds for example; suppose you aren't one, and you want to become one.
What a critter wants has nothing to do with evolution.
You'll need a baker's dozen highly specialized systems, including wings, flight feathers, a specialized light bone structure, specialized flow-through design heart and lungs, specialized tail, specialized general balance parameters etc.
Feathers started out as insulation.
Lighter bone structures make ground bound insectivores faster and better able to get lunch (and not be lunch)
specialized flow-through design heart and lungs
What critter doesn't have a flow through heart???
specialized tail, specialized general balance parameters etc.
Ever watch a cheetah take down an impala? Next time pay attention to how it whips the tail around to maintain balance and enhance maneuverability. It's no less of a problem when chasing scurrying insects.
Well before wings are big enough to sustain flight, they are big enough to help in tight turns. Eat lunch or be lunch.
In probability theory, to compute the probability of two things happening at once, you multiply the probabilities together.
Yeah? That only applies to non-correlated causes. The chance of dying on any given day is pretty low. The chances of being in an accident are only a bit higher (You'll experience more accidents than deaths).
OTOH, the chances of dying in an accident are fairly high.
assuming you were to somehow miraculously evolve the first feature you'd need to become a flying bird, then by the time another 10,000 generations rolled around and you evolved the second such reature, the first, having been disfunctional/antifunctional all the while, would have DE-EVOLVED and either disappeared altogether or become vestigial.
OK, flight feathers. They don't particularly keep a critter warm, but even minimal "flight" feathers increase the ability of a front limb to aerodynamically steer towards a maneuvering prey item without appreciably increasing their weight. Short, stiff feathers good. Very slightly longer stiffer feathers better. Slightly longer stiffer feathers mean the new and improved critter has a bit better a chance to live long enough to pass on its advantage. Much longer feathers and pretty soon the critter's decedents can aerodynamically steer UP towards a flying bug. And the ones who can get the bug that got away? Guess what? They are less apt to starve, and more apt to pass on their genes.
Because there is zero evidence in the fossil record to support any sort of a theory involving macroevolution
Ah! A testable hypothesis! If only the fossil record showed that a small multi-toed critter could change into a large single toed hoofed critter...
Darwinian evolution demanded that the vast bulk of ALL fossils be intermediates
They are. In times of bland environmental change one would expect minimal changes in a critter that was already well adapted to those fixed conditions.
Drop an asteroid on the planet and stir things up? Whole new ball game. The survivors have a zillion new niches to fill. A one-size-fits-all critter isn't well adapted to any particular niche, the ones whose color vision lets them spot ripe fruit tend to hang out together (at the ripe fruit!) The ones with Polaroid glasses can see into water and therefore fish better hang out together (at the shoreline). Pretty soon these two groups aren't on speaking terms.
PE requires an eternal victory of animals specifically adapted to localized and parochial conditions over animals which are globally adapted, which never happens in real life.
What are these "globally adapted" animals?
One of your cohorts actually claimed that the fact that giraffes don't live everywhere was proof positive that giraffes are poorly adapted!
Again, Gould and Eldridge require that the Abracadabra-Shazaam(TM) happen not just once, but countless billions of times, i.e. at least once for every kind of complex creature which has ever walked the Earth.
As opposed to the far more reasonable, and reasoned, stance that every single type of animal was created full formed in its own personal Abracadabra-Shazaam (with the only difference being that in your version it's God who overtly says Abracadabra-Shazaam)
Doesn't sound like you've ever taken any sort of a look at the difference between down (insulation) feathers and flight feathers. The two are gigantically different and the one could not possibly evolve into the other.
Do you know why they make jackets out of down?
Yet there is change over time, or minor changes in existing species (microevolution), neither of which any sane person doubts.
Have you done any real reading about dinosaurs lately, particularly regarding the meat, proteins, hemoglobin, blood vessels, intact skin and other material which is turning up on a number of dinosaur finds and the question of known dinosaur types which turn up in Amerind petroglyphs??
To repeat myself:
Fri Aug 1 10:08:25 2008 · 8 of 13
null and void to wendy1946
Let's see where the data takes us before anyone counts coup here.
Even Especially because 65,000,000 million years is an improbably long time for organic matter to survive this stuff is very interesting.
No matter where the data goes, our understanding of all of creation will be improved.
Perhaps that will mean fossilization and decay processes are far different that we thought.
Perhaps it will mean that everything we know about radioactive decay, geology, cosmology, anthropology, time, and biology needs major revision.
Perhaps our understanding of subterranean bacterial growth in incomplete, and we confused what something looks like for what something is.
Me? I'm hoping it is really bits 'o dinosaur.
That would be way kewl!
(But I repeat myself...)
Tue Jul 29 09:10:50 2008 · 110 of 149
null and void to wendy1946
Which is more probable?
1) Its a stegosaurus, 155,000,000 years away from its normal time.
2) Its an alligator, 700 miles from its normal range.
(But I repeat myself...)
Check out Vine DeLoria's "Red Earth, White Lies". The 70,000,000 year thing turns out to be a fairytale.
In “The Darwin Myth,” by Benjamin Wiker (the most recent book on Darwin that I’ve read), it is recorded that in the first edition of “Origin of Species” “Darwin was silent about God as well, but that silence was transparent in its implications: Darwin had not said anything about God because he had rendered Him entirely superfluous.”
In subsequent editions (beyond the second) Darwin, apparently responding to critics, threw them a sop by writing of “life, with its several powers, having been originally breathed by the Creator into a few forms or into one . . ..”
Dare we hope that the Creator was graciously grateful for this reluctant acknowledgement?
In this same book, p. 47, we find Darwin wondering “why should there be differences (among birds sharing a common gene pool) on nearly identical islands a mere twenty miles apart?” A good question; birds should be capable easily of inter-breeding across so small a territorial range. Continuing, we read “It was in fact because of their very proximity, as Darwin humbly admitted, that he didn’t keep very straight what specimens came from which island.”
I rest my case.
Nope. No spiky tail here. Tail looks kinda puny too.
BTW, The end that bites is much easier to restrain that the end that will repeatedly slap the living crap out of you...
(Do you think early European map makers put "here be dragons" in the unexplored areas because there actually were dragons there?)
Easily? Maybe so, but I doubt a finch would cross 20 miles of open ocean if it didn't have to.
Darwin, apparently responding to critics, threw them a sop by writing of life, with its several powers, having been originally breathed by the Creator into a few forms or into one . . ..
I'm not following you here. Are you complaining that he acknowledged a Creator? I can see how that it wouldn't fit an anti-Darwin/anti-science biased world view, and how that would be disturbing to a fanatic. I don't think you are one though.
Continuing, we read It was in fact because of their very proximity, as Darwin humbly admitted, that he didnt keep very straight what specimens came from which island.
Yes. I suppose the case would be strengthened if he'd lied about it, or if hundreds of other scientist didn't go back to the Galapagos and personally check his observations.
I rest my case.
No, as was quite plain, I neither complained nor rejoiced that Darwin grudgingly allowed that a creator might have breathed life into one or more forms of life.
It is clear that no matter what I write, or read, nor whom or what I quote, your opinion of my supposed beliefs and convictions remains fixed.
'have to' is the key.
Follow the mating habits of the penguins, and explain why they trek 50-100 miles to the most uninhabitable part of the planet to reproduce.
You say that as if you are the only one it happens to.
What a critter needs has everything to do with evolution.
Follow the mating habits of the penguins, and explain why they trek 50-100 miles to the most uninhabitable part of the planet to reproduce.
If you are saying that because a critter "needs" a longer neck to reach the tasty leaves, it will grow one, no. That's the Lamarckian theory of evolution. Stalin loved it, as it meant that if you beat people into the proper mold, you could create the "New Soviet Man".
This time you get the missing words award: "to survive".
What a critter needs to survive has everything to do with evolution.
In times of hardship the members of the population with longer necks eat just a little bit better than their short-necked cousins. Sometimes that makes the razor thin difference between starving and barely surviving.
The short-necked cousins really needed a longer neck to survive. They didn't have one. They didn't survive. Or leave descendants.
The ones that live long enough to reproduce have an input to what the next generation looks like. The ones who don't simply don't. Unfortunately, neither you, nor I, nor any living creature "needs" to survive. We all die in the end anyway.
(Although I will allow the possibility that members of 'the last generation' need never die)...
What a critter needs to survive has everything to do with evolution.
Unfortunately, neither you, nor I, nor any living creature "needs" to survive.
This last quote sounds more like the thoughts of Stalin.
If you are saying that because a critter "needs" a longer neck to reach the tasty leaves, it will grow one, no.
Not odd. Predictable, yes.
The problem stems from the conviction that one knows the truth, and that the opposition are idiots with false beliefs.
The truth is that we really just don't know exactly how it all works (life, evolution), nor how in the heck it all even started.
Aye, but giraffes didn’t get longer necks because they wanted them.
No single giraffe ever wished its neck longer, but ones who already had longer necks could gather more food and had a better chance of passing on their long neck genes.
Really no different than making a wiener dog breed out of generic dog stock.
Just in one case humans determine who wins the reproduction lottery, and in the other nature “selects” the survivors.
Arguably the most accurate, rational and sane comment ever made on a crevo thread.
(It doesn't change the fact that I'm right, you're wrong, and that settles it!)
Well, at least you are honest.
Due to the environmental conditions (competition with other 'leaf eaters'), they certainly needed them.... to survive.
We are becoming a bigger factor in the selection process. Not only through selective reproduction, but through alteration of environment.
Yeah. In spades!
Note: this topic is from 12/16/2009."If you have continents splitting apart, you get isolation," says Nesbitt. "So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related, endemic radiation... But that is what we don't see in early dinosaur evolution," adds Nesbitt... three distantly related carnivores in the fossil-rich, Late Triassic beds, implying that each carnivore descended from a separate lineage before arriving in North America, instead of all evolving from a local ancestor. In addition to Tawa, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America. The two- to four-meter-long skeletons of Tawa display characteristics that exist in both of its contemporaries, and features found in neither, implying a separate lineage. Unlike many theropods, Tawa's lineage does not lead directly to birds. According to Nesbitt, the old view held that Herrerasaurus split off of the family tree after the ornithischians, but before the sauropods and theropods diverged. "Tawa now appears to show that the three groups split from each other as soon as dinosaurs evolved," he adds, though paleontologists have not yet found a concrete example of a dinosaur that existed before the divergence.Thanks null and void.
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Thanks null and void.