REMNANTS OF LOST SPECIES: The crurotarsans lived a parallel existence to dinosaurs, but did not last as long as the mighty dinos.
Image: Image courtesy of Stephen Brusatte, Columbia University
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Dinosaurs' long reign on Earth may have had more to do with lady luck than with superiority, according to a study published today in Science. The study challenges the old notion that dinosaurs out-competed their reptilian contemporaries.
It is a longstanding mystery why dinosaurs became and remained so plentiful for more than 180 million years. The traditional theory: dinosaurs suddenly replaced other land animals because of special traits that gave them an evolutionary advantage, such as being warm-blooded, nimble and able to occupy varied habitats. This new research presents a fresh mathematical analysis of previous fossil data that indicates that ancestors of modern-day crocodiles had as diverse body types as early dinos, with whom they co-existed for some 30 million years.
Although the data doesn't directly contradict the idea of dinosaur superiority, the authors say it is likely that these crocodilians were even more successful than dinosaurs, the latter of which may have survived major extinctions due to sheer luck.
"If you dissect the past, you can see that luck is a big part of everything in the grand scheme of evolution," says lead author Stephen Brusatte, a researcher at the American Museum of Natural History.
The idea that dinosaurs lived at the same time as similar reptile species is nothing new. And data from the past few years has many paleontologists rethinking whether dinosaurs were really so special after all. The fossil record shows that dinos lived alongside comparable groups of reptiles for millions of years without overtaking them.
For example, the early dinosaurs were contemporaries of crurotarsans, croc ancestors, during the late Triassic period about 230 to 200 million years ago. This reptilian group ranged from quick predators to two-legged vegetarians to leisurely grazers. Then, as the Triassic turned into the Jurassic, the creatures roaming the planet changed drastically. Most crurotarsans disappeared from the fossil record. But many dinosaurs survived—and flourished, diversifying into meat-eating giants, armored warriors and winged aviators.
Brusatte and researchers from the University of Bristol in England expanded this research by analyzing the existing fossil record to show crurotarsans may have even been more successful than dinos. First, the team constructed a new family tree to separate the dinosaurs from the croc ancestors. They then assembled a database of 65 dinosaur and crurotarsan species that included over 400 skeletal features, such as whether they had beaks or shorter arms than legs.
If dinosaurs were more fit for the environment, they should have had a higher rate of evolution and more diverse body types. Instead the researchers found that the two groups evolved at similar rates and that the crurotarsans had a wider range of body types, suggesting that they had actually adapted to more lifestyles and ecological niches.
The authors argue that because dinosaurs and crurotarsans were living parallel lives together for so long, it is unlikely the dinosaurs necessarily ruled. If you could travel back to the Triassic, Brusatte says, you would have guessed that the crocodilians would have won out. "There's no way you could argue that dinosaurs were superior to them," he says. Instead, he thinks an extinction event at the beginning of the Jurassic some 205 million years ago—like runaway global warming or an asteroid crash—may have just been bad luck for the crurotarsans.
Many paleontologists consider these findings a major step in dinosaur science. "It's really refreshing," says Kristi Curry-Rogers, a dinosaur paleontologist at Macalester College in Saint Paul, Minn. "It definitely challenges the standard story of dinosaur evolution…. In the world of dinosaurs, we see a lot that portrays them in ways that science doesn't really follow."
But not all experts agree. "I think that the conclusions of the authors aren't warranted," says Kevin Padian, a dinosaur paleontologist at the University of California, Berkeley. "Good luck isn't an evolutionary force…. Extinctions aren't random." He believes that dinosaurs are different enough from crurotarsans that they may have had a competitive edge.
Whether dinosaurs rose to fame from fitness or a roll of the dice should become clearer as paleontologists discover more fossils to fill in the sparse record of dinosaurs' early history and elucidate what caused the extinctions at the end of the Triassic. Rogers says that Brusatte's analysis will probably challenge people to support their claims of dinosaur superiority with stronger evidence. "It gives people something to shoot at that is based on data," she says, "and not just assumption."
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23 Comments
Add CommentObviously part of the big plan of Intelligent Design!!!!!!
Reply | Report Abuse | Link to thisDr Kevin Padian of U.C. Berkeley makes the strong case,"LUCK" is NOT an evolutionary force! Why not make a new case, that the crurotarsons "UNLUCKY", as opposed to the assumption that it is the dinosaurs that were lucky? But first let's take another careful look at the nature of evolutionary forces!
Reply | Report Abuse | Link to thisI would prefer to say the Earth enjoyed a significantly different environment in the Prehistoric 'solar' system. Gravity, I believe, is not such an immutable feature as we have presumed. Triassic and Jurassic were peaks in our low gravity periods, allowing super growth and massive bodies that are unsustainable now.
Reply | Report Abuse | Link to thisMajor global/ solar catastrophes mark the end of each period wiping out most species, accompanied by extremely high crustal temperatures. Thus imprisoning the fresh carcases in instant-solidified sand/mud = fossil record.
That's my logical thoughts.
where did you read that gravity can fluctuate during periods? sounds very absurd although I'm intrigue, if it's just an internal theory of yours I'll chalk it up as crazy :)
Reply | Report Abuse | Link to this"Extinctions aren't random"?! I think that one could argue that the dinosaurs themselves became extinct under extremely random and unlucky circumstances caused by a meteor!
Reply | Report Abuse | Link to thiswell... easy comes, easy goes.
Reply | Report Abuse | Link to this"where did you read that gravity can fluctuate during periods? sounds very absurd "
Reply | Report Abuse | Link to thisIt won't be find in your average textbook, but on a very informative website we find the following:
Ted Holden has resurrected the controversy by examining the relationship of size, weight, and strength in animals. (His analysis was the basis for a documentary televised in Japan in Feb, 2004....
Strength is proportional to the cross section of the muscle: If one muscle is two times the diameter of another, the first will be four times (the square of two) as strong. But weight increases with the volume: A muscle that's twice as big will weigh eight times (the cube of two) as much.
Holden computed the weight/strength ratio of a well-trained human weightlifter and scaled it up to the size of a dinosaur. The weightlifter soon became too big to lift his own weight. Strength, in its relationship with weight, imposes a limit on size. Holden's calculations indicate that the heaviest elephants of today approach that limit.
The largest dinosaurs are many times the size of an elephant. And dinosaur skeletons aren't as well-designed for bearing weight as elephant skeletons. Dinosaurs are impossibly large for planet Earth, but their bones are proof that they must have existed. How could that be?
The limit on size depends on weight, and weight depends on the force of gravity. Most conventional theories assume that gravity throughout the universe has always been and will always be a constant property of matter. But that's only an assumption, and it must be verified empirically.
...Holden calculates that in order for the largest dinosaurs to function, gravity must have been at least 1/3 (and possibly as low as 1/4) what it is today. He also postulates that gravity increased suddenly at the close of the age of dinosaurs but not to the present value.
Continuing his arguement continues:
Lower-than-present gravity continued into the following ages of giant mammals and possibly even to the days when early humans were building giant monuments like Stonehenge.
http://www.thunderbolts.info/tpod/2005/arch05/050623impossible-dinosaur.htm
Actually... increasing diameter by 2 would increase weight by 4 times, not 8 (assuming the length is unchanged). Meaning that scaling up really has no effect on anything at all.
Reply | Report Abuse | Link to thisThe formula for volume is L*W*H, and changing diameter only changes 2 of those variable, so it would have 4 times the volume, and assuming density stays the same (not very likely that it alters by much more than about 5%) the weight of it increases by only 4 times. Thus strength increase of 4 times is equal to weight increase of 4 times. The only negative of scaling a creature up in size is that it requires more food, which became unavailable around the end of the dinosaurs due to the debris from the meteor.
The Gravitational Force of the Moon on Objects on the Earth
Reply | Report Abuse | Link to thisJust as the Earth pulls on the Moon, the Moon pulls on the Earth, and everything else in space. The strength of the Moon's gravitational force is given by Newton's Law of Universal Gravitation
F = G m MMoon / r2Moon ,
where G the gravitational constant, m is the mass of the object being pulled on by the Moon, MMoon is the mass of the Moon, and rMoon is the distance between the Moon and the object. A similar force acts between the Earth and various objects, except that we use the distance to the Earth, rEarth, and the mass of the Earth, MEarth, in place of the lunar values. Since the Earth's force on something is the object's weight, W, we can write
W = F = G m MEarth / r2Earth .
MMoon / MEarth is about 1/80; and for an object at the surface of the Earth, rEarth is about 4000 miles, and rMoon is about 240,000 miles, or 60 times greater; so at the surface of the Earth, the pull of the Moon is 80 times smaller than the object's weight because of its lesser mass, and another 3600 (= 60 squared) times smaller because of its greater distance. Combining these two effects, the Moon's pull on objects near the Earth is only 1/300,000th of their Earth weight. So if something weighs 150 pounds due to the pull of the Earth, the pull of the Moon on that object would be about 150/300000, or 1/2000th of a pound. This is a very small force, but it produces a number of interesting effects, because it acts on every object near the Earth, including the Earth itself.
Two points:
Reply | Report Abuse | Link to this1 Despite assertions to the contrary, at least some extinctions can be the result of external events having nothing to do with a species genetic fitness. Extinction: Bad Genes Or Bad Luck? By David M. Raup makes a good case, using several real-life examples, although it focuses too much on cosmic speculation IMO.
2. The confusion expressed here about strength vs weight is in part the result of how the point was originally presented. The case is when you double the SIZE of a muscle, or a bone, or just about anything, its strength is doubled, because strength is porportional to cross-section, or length times width, BUT its weight is tripled, because weight is porportional to volume, or length times width times height. Which is why dik-diks don't look like scaled-down Kudus. Sabe?
Willynilly
Reply | Report Abuse | Link to this1) I have never thought fossils were caused by unfitness or normal death. From the amazing state of preservation of even one sample in each strata it has got to be a unique event - unlike anything we have experienced in the last 1000 years or so. Intense heat from within the crust, globally, points to a sudden change in Earth's rotation eg an axis shift or even reversal. A very big external force was needed - a lot bigger than than most meteors or asteroids.
2) Thanks for all the math help (inc Alway). If diameter changes without length then 'pi r squared' gives a 4x increase in volume - hence weight. But enlargement in 3D would be 8x? Either way the point is that weight & bone structure are limiting factors as Ted Holden says "Strength, in its relationship with weight, imposes a limit on size." The advantage of size could be outweighed by lack of mobility, if our current gravity existed in earlier times.
I read that many dinosaurs grew at prodigious rates, presumably to ensure their survival. The bones are seen under microscope to be virtually hollow. Would that also give them reduced strength to resist gravity OR was strength not such an issue to 1/3 gravity??
The method by which gravity operates is unclear. A new suggestion has been that each atom of matter responds to its neighbours - to constantly maintain its neutrality. In this theory, the negative 'electron' consists of v.fast orbiting subtrons that respond instantly to adjacent atoms, by adjusting their dipolar configuration. This is more of an electric charge balancing arrangement and therefore will not fit well with standard mechanical Newtonian/ Einsteinian models. I like it for its extreme simplicity. Do we know what interactions occur between rotating, magnetic bodies immersed in charged particle streams (solar electric currents?) Is Newton's "G the gravitational constant" really constant?
Earth's surface gravity was less during the Permian and the entire Mesozoic than it is today. This is explained in a new book 'The Gravity Theory Of Mass Extinction' which links the movement of tectonic plates to the shifting of the Earth's inner core. The movement of the inner core away from Pangea caused the reduction in surface gravity.
Reply | Report Abuse | Link to thisA pulse in increased gravitation at the Triassic-Jurassic boundary, related to the tectonic activity that began the formation of the incipient Atlantic Ocean, was the cause of the crurotarsan extinctions. They had spalyed legs.......a big disadvantage compared to the dinosaurs.......when the surface gravity increased.
I'm kind of confused. I don't know that much about science compared to you guys and this has nothing to do with the article. I thought that the astronauts that lived in the space station saw their bones deteriorate due to weightlessness. How can bones of dinosaurs be 2 or 4 times stonger if they lived in a 1/3 or a 1/4 of what the gravity is today?
Reply | Report Abuse | Link to thisIf the weight calculatoins where all amde from a human weight lifter then they are seriously flawed. Humans have very low muscle density and low muscle protein density. As an example, many apes have up to EIGHT TIMES the muscle density of humans and they are very much stronger than we are even though they are often smaller. So muscle size and weight cannot be used alone to determine the strength of a muscle. There is a lot of molecular biology involved in muscle strength that we just cannot test. In other words, there's not a lot you can tell about the strength of a muscle of a particular animal without being able to test the actual animal. You can make assumptions, but they'll probably be wrong. I think the bones would be a much better indicator of strength.
Reply | Report Abuse | Link to thisThe title and topic of this article made me angry. We are trying very hard to get the not so reasonable thinkers to think reasonably. Introducing "luck" into any science article is like saying it's OK to talk about ID, astrology and invisable elephants.
Reply | Report Abuse | Link to thisBy using "luck" to think about evolution/ extinction, does that mean we can just chalk up the human caused extictions to bad luck?
Dynamic model of the Earth site www.mammoths.narod.ru has proved changes with which processes of III natural phenomenon have affected ,not in general on a planet but accordingly
Reply | Report Abuse | Link to thiszones (h1-h5) and how these changes on continents to flora fauna and practical activities homo sapiens in the specified zones were accompanied
Dynamic model of the Earth site www.mammoths.narod.ru has proved changes with which processes of III natural phenomenon have affected ,not in general on a planet but accordingly
Reply | Report Abuse | Link to thiszones (h1-h5) and how these changes on continents to flora fauna and practical activities homo sapiens in the specified zones were accompanied
Good work y'all :)
Reply | Report Abuse | Link to thisDinosaurs romed for 183 million years. The yale museum has a 5 fingered dinosaur that cound not compete with the three fingered , claw in the middle that could grap 40 pounds of meat on the run!
Reply | Report Abuse | Link to thisWhy did'nt they develope a large intellegent brain? We have theoretically added our brain on top of the reptiles ,fish , amphibians and others.
Not logical. Our golden age is gone, past , no more discoveries like we have had.
The large igneous basalts, flood basalts , over the past 250 million years are in 97.7% with extinction events. Explain that one in one paragraph!
Reply | Report Abuse | Link to thisRead Delano's Discovery-lulu google it.
Ice cap moving front scrapped the front area of the ice shell flow eliminating the fossils, interpretered as extinctions.
The rear of the flow 24 million years laaer and 2,400 miles to the rear the shell's trailing edge was spewing lava and building "steps, Siberian, and traps Decan". Erosion wiped out 50% of the large igneous providence.
Delano's Discovery-lulu "google it".
cigarshaped, the best way to learn about a field of study is not to sweep all the cards off the table and start again. It is much more likely that dinosaurs were physiologically different than humans (which we know to be true) than it is to posit large fluctuations in gravity for no apparent reason to try to equate them. A little knowledge is dangerous and using a little math to justify it hardly seems to account for the contradictory evidence, and the effects on the solar system and universe as we know it.
Reply | Report Abuse | Link to thisYes, the mass of the Earth is changing, mostly due to added mass, we know that. But the depth at which the fossil record is being found is an excellent first order indication of the change of mass since that time and the effect is insignificant. If the Earth's gravity were changing by 1/3 as you state, have you thought what that would do to the Earth's orbit or the Moon? That's a way bigger problem than believing that dinosaurs were different than we are. I'd encourage this Holden guy to go talk to a few astrophysicists for a start, and then go back to the drawing board and look for a more subtle effect
All of today's crocodilians live in or near water. Unless some ancient ones followed a different pattern and could survive away from water, a large drought over much of the earth would have wiped out many of them leaving the dinosaurs. Also today's crocodilians are tropical or subtropical. When Pangaea broke up, colder weather could move closer to the poles and the crocodilians became restricted to a smaller area.
Reply | Report Abuse | Link to thisLower surface gravity permitted some dinosaurs to each their great size. This is explained by The Gravity Theory of Mass Extinction (www.dinoextinct.com).
Reply | Report Abuse | Link to thisSurface gravity on the Earth, particularly when large supercontinents exist, can be altered significantly. The mechanism is the offsetting of the Earth's core elements (inner/outer cores and densest part of lower mantle)away from Earth-centricity. This offsetting is directly related to the latitudinal movement of the supercontinents guided by the law of conservation of angular momentum.