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Thread: How many dinosaurs ever existed?

  1. #1 How many dinosaurs ever existed? 
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    I was thinking about how rare it must be to find a dinosaur fossil and got to thinking about how many potenital fossils there could be. This all depends on on many dinosaurs ever existed. Dinosaurs were around for over 160million years. So if 100million were born a year that would be sixteen quadrillion (16x10^16) dinosaurs ever. It really shows what a low probability it is for a dinosaur fossil to survive until today.

    Comparebly, from this website:
    http://www.prb.org/Articles/2002/How...edonEarth.aspx
    about one hundred billion (10x10^10) have ever existed. This also leads to the question of what type of fossils would we leave for 100 million years in the future?


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    Universal Mind John Galt's Avatar
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    You make an excellent point. The difficulty of preserving remains long enough for them to become fossilised is immense. Predation and scavenging account for a very large percentage. Then only a small proportion of those will find themselves in sediment that is destined to be buried and eventually become rock.

    A further calculation could look at what percentage of that material is actually exposed in surface layers where we can access it. That is also a very small number.

    The surprising result is that we find as many fossils as we do, a fact never appreciated by creationists. Indeed a recent survey showed there was a 10^9 greater possibilty that a creationist would bury their head in the sand than would a dinosaur.


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    when you say dinosaurs are you referring to the giant reptilian beings only? Would a fossilized sea-creature or a shellfish like creature count?

    There is lots of life on this planet, but even then I find 16*10^16 a huge number.

    Let's make a theoretical point:
    Assuming that the earth was populated with dinosaurs, as it is currently populated with humans, at the time they went extinct. (this was due to a meteorite seems to be the accepted explanation).
    There would then be 6+ billion dinosaurs. Each one of them several times larger than a human being.
    now assuming again that each generation would hold the same ammount of dinosaurs (just for math's sake) you would need 10.000.000 generations of dinosaurs to get to 6*10^16 dinosaurs.
    That seems like a lot. I am no archeologist, nor have I ever studied the dinosaurs in this way, but could you link the study where you got that number? I'm interested as to how they got to it
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    Quote Originally Posted by toonb
    There would then be 6+ billion dinosaurs. Each one of them several times larger than a human being.
    Many dinosaurs were as small as a large chicken. (Some of them eventually became large chickens.) So the six billion number is probably too small by almost an order of magnitude.

    Even so, staying with your numbers, you estimate 10,000,000 generations. Dinosaurs were around for about 170,000,000 years, so we can accomodate your generations in that time if each generation is seventeen years or less. That seems reasonable.
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    Ok. Thank you that number makes sense now .

    Is there some sort of 'definition' to check if something is a dinosaur? Like for example, did they have to have a certain skintype, digestive system, habitat?
    Would a long extinct giant version of a crab (assuming they find one) be considered a dinosaur?

    They allways make me think of the movie Jurassic Park, but I'm curious as to what dinosaurs actually are in all diversity. Not just in Hollywood
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    Time Lord Paleoichneum's Avatar
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    Quote Originally Posted by toonb
    Ok. Thank you that number makes sense now .

    Is there some sort of 'definition' to check if something is a dinosaur? Like for example, did they have to have a certain skintype, digestive system, habitat?
    Would a long extinct giant version of a crab (assuming they find one) be considered a dinosaur?

    They always make me think of the movie Jurassic Park, but I'm curious as to what dinosaurs actually are in all diversity. Not just in Hollywood
    The easy way to tell is to check if the animal was included, in its scientific description, in the Reptile superorder Dinosauria. Thus if it is not reptialian, such as your crab, then you can immediately discard it as a possible dinosaur.

    Also of note is that dinosaurs were almost exclusively terrestrial, so if it was aquatic in life you can exclude it. The only grey area is where one wants to follow on the line between "dino" and "bird".
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    Quote Originally Posted by Ophiolite
    The surprising result is that we find as many fossils as we do, a fact never appreciated by creationists. Indeed a recent survey showed there was a 10^9 greater possibilty that a creationist would bury their head in the sand than would a dinosaur.
    Pure awesome.
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    Quote Originally Posted by Paleoichneum
    Quote Originally Posted by toonb
    Ok. Thank you that number makes sense now .

    Is there some sort of 'definition' to check if something is a dinosaur? Like for example, did they have to have a certain skintype, digestive system, habitat?
    Would a long extinct giant version of a crab (assuming they find one) be considered a dinosaur?

    They always make me think of the movie Jurassic Park, but I'm curious as to what dinosaurs actually are in all diversity. Not just in Hollywood
    The easy way to tell is to check if the animal was included, in its scientific description, in the Reptile superorder Dinosauria. Thus if it is not reptialian, such as your crab, then you can immediately discard it as a possible dinosaur.

    Also of note is that dinosaurs were almost exclusively terrestrial, so if it was aquatic in life you can exclude it. The only grey area is where one wants to follow on the line between "dino" and "bird".

    this makes me wonder how many fossils are under water in places that didn't used to be underwater. Kind of the opposite effect of paleontologists finding aquatic fossils on mountain tops.

    *don't know why quoting isn't working
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    Yeah, I've allways thought the bodom of the ocean held much more mysteries and discoveries than most of us currently are aware of.

    But to go in a little deeper, Paleoichneum, what would be required for an animal to get the Dinosauria superorder? Where does science draw the line?

    ps: pretty much all code tags haven't worked for me since day 1. quoting, URL, image tags and Tex have failed for me so far. Maybe they just don't work at all atm
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    Universal Mind John Galt's Avatar
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    Quote Originally Posted by toonb
    But to go in a little deeper, Paleoichneum, what would be required for an animal to get the Dinosauria superorder? Where does science draw the line?
    There is one version of the Dinosauria cladogram here.

    The wikipedia article is also a good place to start. This is a short extract from that article:
    Under phylogenetic taxonomy, dinosaurs are usually defined as the group consisting of "Triceratops, Neornithes [modern birds], their most recent common ancestor, and all descendants." It has also been suggested that Dinosauria be defined with respect to the most recent common ancestor of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs, including theropods (mostly bipedal carnivores), sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails), ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (herbivorous quadrupeds with horns and frills), and ornithopods (bipedal or quadrupedal herbivores including "duck-bills"). These definitions are written to correspond with scientific conceptions of dinosaurs that predate the modern use of phylogenetics. The continuity of meaning is intended to prevent confusion about what the term "dinosaur" means.
    There is a wide consensus among paleontologists that birds are the descendants of theropod dinosaurs. Using the strict cladistical definition that all descendants of a single common ancestor must be included in a group for that group to be natural, birds would thus be dinosaurs and dinosaurs are, therefore, not extinct. Birds are classified by most paleontologists as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs.
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    Quote Originally Posted by Ophiolite
    Even so, staying with your numbers, you estimate 10,000,000 generations. Dinosaurs were around for about 170,000,000 years, so we can accomodate your generations in that time if each generation is seventeen years or less. That seems reasonable.
    Seventeen years sounds rather long, actually. Even huge species like T.rex only reached a maximum age of around 28, with the average (especially factoring in the high mortality of young individuals) of much less.
    I remember reading an article some time ago about some herbivorous species having extremely rapid growth (reaching a very large body size in only four years) as an adaptation to help avoid predation. Their generation time would likely have been much under 17.

    I would agree that the number of dinosaurs is likely much greater than that figure.
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    Quote Originally Posted by C.Elrod
    Seventeen years sounds rather long, actually.
    I agree, but since I was seeking to demonstrate that there was enough time to accomodate the 10,000,000 generations toonb felt would be necessary. Using a longer time between generations than is likely removes the possibility of being accused of trying to make the data look good.
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    Quote Originally Posted by toonb
    Yeah, I've allways thought the bodom of the ocean held much more mysteries and discoveries than most of us currently are aware of.

    But to go in a little deeper, Paleoichneum, what would be required for an animal to get the Dinosauria superorder? Where does science draw the line?

    ps: pretty much all code tags haven't worked for me since day 1. quoting, URL, image tags and Tex have failed for me so far. Maybe they just don't work at all atm
    Im sure there are vast deposits of fossils under water where they are currently inaccessible.

    Ophiolite posted the more complex definition of what you were asking, but basically something has to be closer in relationship to Megalosaurus or Iguanadon then to crocodiles, or pigeons (i think is the bird normally used).
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  15. #14  
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    A fossil must have the following characters before it can be called a dinosaur:

    -three or more sacral vertebrae

    -shoulder girdle with backward facing glenoid

    -asymmetrical manus with less than or equal to three phalanges on digit IV

    -an acetabulum with an open medial wall

    -tibia with cnemial crest

    -astragalus with long ascending process that fits into the anterior part of the tibia

    -sigmoidally shaped third metatarsal

    -postfrontal bone absent

    -humerus with long deltopectoral crest

    -femur with ball-like head on proximal end


    Introduction to the Study of Dinosaurs by Anthony Martin, 2001.
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