Monday, June 21, 2010

Inaccuracy in Paleontology: Spider Edition

Here we have a page from the 1999 Scholastic-published book "Dinosaurs to Dodos" by Don Lessem. You'll notice the gigantastic tarantula chasing a giant 6ft long megamillipede of the Silurian.

Read the text: Megarachne is described as a foot across in the body and extrapolated to a span of 8 feet. I couldn't remember reading about any 8 foot spider anywhere, so I went to teh Google and found that 'Megarachne' is an odd eurypterid (sea scorpion) that was originally identified as a spider, and reinterpreted in 2004. http://scienceblogs.com/laelaps/2010/03/megarachne_the_giant_spider_th.php

Now this was from 1999 so the spider thing is forgiveable, but... everything I read about the fossil on the web said that the leg-span was estimated at around 20 inches. INCHES. Where the hell did they get 8 feet from?? Isn't this guy a super scientastic paleoperson?

An amazing example of inaccuracy, and only from 10 years ago. Amazement!
Then again, I'm open to any reasonable explanation of this...



17 comments:

  1. I never ever read anything about 8 feet prehistoric spiders either... This is the stuff nightmares are made of.

    Though it's an hypothesis that those kind of spiders would be a no no evolution/survival wise.

    surface increases as the square of the length, but volume increases as length's cube. that means that the ratio between contact surfaces (ie the spiders legs' ends) and actual weight of the spider would be strongly modified should the spider keep the same proportions as her smaller counterparts. this would result in a hugely increased pression on the leg's end, and would render the spider unable to move. her legs wouldn't carry her.

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  2. Yes, this is true. Except that the atmosphere is the Silurian was different, and highly oxygenated, which enabled the gigantic dragonflies and millipedes, etc, to function on land. I suppose an 8 foot spider MIGHT have been possible, but... I know not much about those physic but it seems rather extreme.

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  3. The high oxygen concentration would probably enhance their metabolism, but even with that the spider would simply lack the muscle mass. No amount of oxygen would help her as it's a different matter I think.

    I don't think oxygen concentration would change the air's density too much either and the graviational pull wasn't that different from now.

    I wasn't there, so I can't be 100% sure, but from a physic standpoint it seems impossible.

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  4. I'd have to read more... since perhaps the physics of a spider are diff. from a dragonfly? like i said seems a bit off to me too.

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  5. Tell me, what enabled dragonflies to function properly on land? What did the increased oxygen concentration do? I'm curious about that.

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  6. http://www.nap.edu/openbook.php?record_id=11630&page=89

    A chapter about Silurian atmosphere and transition to land... but as I've read before, the emphasis is always on increased oxygenation promoting large growth. And adaptation of their gills and breathing mechanisms, as well as exoskeletons, supporting them on land.

    http://en.wikipedia.org/wiki/Meganeura The large dragonfly had a wingspan of around 2 feet.
    http://www.palaeos.com/Invertebrates/Arthropods/Arthropleurida/Arthropleurida.htm Giant millipede...

    I guess a 2 foot span spider might be possible considering these, the largest living spider has a span of about 12 inches (sry I don't know the conversion to cm, my country is dumb and I'm bad at mental math)

    but EIGHT feet? Huh... yeah

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  7. Apparently the growth factor is bacause of the lousy respiratory system of tjose species. in today's atmosphère their bodies could not distribute oxygen efficiently, but in the past the much greater oxygen concentration allowed for larger sizes while keeping oxygen nicely distributed over the body. It was true for spiders too, so giant spiders were a possibility. But only up to a certain point, and 8 feet spiders are a bit far fetched from a physic standpoint.

    As spiders have an exoskeleton, the strain on the joins caused by such a big upscaling would be too hard, requiring something similar to diamond to resist (this was actually simulated for giant ants, as spiders also have an external skeleton, I think it applies too, but I'm not 100% sure) because they do not have the large, round lubricated contact surfaces between segments that internal skeletons provide.

    Another interesting fact is that spiders lack muscles to extend their legs, they can only contract them. to extend them back, they have to force bodily fluids into the legs. For an 8 feet tall spider it would require a very large amount of fluids and a great deal of internal pressure.

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  8. Yes I suspected that the long legs would be a barrier for their size. But I am not very well read in physics altho I've read a bit about the mechanics of animal physiology (related to studying living species' size/limbs/speed etc to estimate how dinosaurs moved, and that sort of thing)

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  9. awesome, biomechanics must be very interesting. You'll have to tell me about it, even more if it's about dinosaurs.

    Sorry if I bored you with my physics ramblings.

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  10. Nah it's not boring. I'm just bad with numbers and haven't studied hard physics beyond whatever we learned in high school... haha.

    I'm no expert in biomechanics either, but it's pretty interesting-- a good example to read about would be how they analyzed dinosaur trackways to figure out the size and speed of what made them, or the debates over how quickly dinosaurs could move.

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  11. That would be an interesting read, I'll have to dig around. Another subject I enjoyed reading about is the theories about dinosaurs being able to swim.

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  12. Check out the link on my sidebar for Tetrapod Zoology. I've been rabidly reading it for a few years, and he does many interesting posts -- just the other week he posted something he was studying about computerized models analyzing whether giraffes can swim.

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  13. Will do. Thanks for the link.

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  14. No problem, I pimp Naish's blog all the time cos it's so ridiculously awesome. He discussed all sort of zoological stuff- dinosaurs, cryptozoology, all groups of animals. It's really educational.

    He's also a researcher of British theropods has put out science papers, and written a book recently. I wanna be like him when I grow up lol (as a kid I wanted to be a paleontologist)

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  15. Sounds like a lot of good things to read.

    I had the same dream as a kid. I kind of regret the way things went.

    I Hope your dream job will come true!

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  16. Hehe I kinda doubt it, since I'm not that good with the extremely technical part of science, and you need tons of higher level education and research to really do anything substantial in it. I don't recall exactly, but one blog I was reading mentioned the estimate for how many dinosaur paleontologists worldwide really make a serious living/career out of it (are published, well known etc) it was something like from 80 - 100 IIRC. Naish writes about his situation a lot, kind of sporadically writing papers, collaborated with other researchers, doing freelance writing but other stuff on the side to supplement it. It's a really academic kind of world from what I've gathered.

    I wish I could have done that, kind of -- I think it's sad that so few women get into that field. There are some women who are paleo-artist though, which is cool.

    i guess I go more towards the art/amateur side of it, it entertains me and inspires me artistically.

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  17. I was hell bent on trying to be a paleontologist, but as you said, it's not an easy career to get in.

    Things kind of go too fast, too. I ended up in quantum physics, then biophysics/medical physic, and then where I am now. Guess I had my reasons for the last part, though. I really hope you can work in the field of your choice.

    Well I've been to your other DA account, and you really are talented. Ever thought of doing a recueil of your illustrations? I'd buy it in a second, just to have the pleasure of turning the pages and look at your drawings when I want.

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