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Natural Environment How Human History has been impacted by the environment, science, nature, geography, weather, and natural phenomena


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Old June 22nd, 2014, 10:15 AM   #51

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I'm curious, why were so many prehistoric animals way larger than their modern counterparts? And why did they become extinct?
The large ones were harder to wash/drag away, so they managed the fossilization process more successfully. But there are myriads of little critters too. I spent one summer removing matrix from fossils collection in the Antarctic, and I was sternly advised that ANYTHING that looked like something other than rock was to be brought to the lab manager's attention immediately and before proceeding a nanometer further. (I had to look up nanomter. )
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Old June 22nd, 2014, 11:59 AM   #52

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There were several reasons that animals in the past were larger than their modern counterparts. The main reason is that there was more oxygen in the atmosphere, facilitating the growth of larger animals. I know that there were other reasons, but that is the only one I know for sure. The reasons that 99% percent of all species are now extinct is that they were either unable to adapt to their circumstances properly or simply evolved out of existence.
Being warm-blooded might place a greater limit on size than being cold-blooded. The largest dinosaurs by far were the sauropods, who may have been cold-blooded.

Dinosaurs also had bird-like bones with air sacs in them that made their bones lighter without sacrificing strength. The design of their bones allowed for quite massive sizes in some species.

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Old June 22nd, 2014, 12:18 PM   #53

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Being warm-blooded might place a greater limit on size than being cold-blooded. The largest dinosaurs by far were the sauropods, who may have been cold-blooded.

Dinosaurs also had bird-like bones with air sacs in them that made their bones lighter without sacrificing strength. The design of their bones allowed for quite massive sizes in some species.
I'm not so sure. The largest creature (we know about) that ever lived is still living today - the Blue Whale. The largest land animals of all time were dinosaurs, but some immense mammals have existed too. Baluchitherium would've been considered fairly large even by dinosaur standards (not compared to the great sauropods though!). Most dinosaurs weren't huge, but of course the ones that the public loves so much were massive That being said I think overall that the dinosaurs were, obviously, larger than the mammals which came later. Maybe it has something to do with the more oxygen rich environment the dinosaurs inhabited?

I think my favorite misconception about dinosaurs comes from fans of the Jurassic Park movies. Velociraptor was a very small dinosaur, roughly the size of a turkey, yet thanks to Spielberg 99% of the public thinks Velociraptors were man sized
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Old June 22nd, 2014, 12:19 PM   #54

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The large ones were harder to wash/drag away, so they managed the fossilization process more successfully. But there are myriads of little critters too. I spent one summer removing matrix from fossils collection in the Antarctic, and I was sternly advised that ANYTHING that looked like something other than rock was to be brought to the lab manager's attention immediately and before proceeding a nanometer further. (I had to look up nanomter. )
Excellent point about fossil size.
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Old June 22nd, 2014, 02:00 PM   #55

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Maybe they ate everything
"Maybe" but not likely. They lived in a swampy area, their teeth are straight, giving the indication that they're intended to hold slippery fish, and that sail would be too brittle to take it into a fight with any large animal.
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Old June 22nd, 2014, 02:06 PM   #56
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"Maybe" but not likely. They lived in a swampy area, their teeth are straight, giving the indication that they're intended to hold slippery fish, and that sail would be too brittle to take it into a fight with any large animal.
What was the sail for? Other dinosaur with sails use to fill them with blood to try and scare a usually more dangerous dinosaur. Why would a dinosaur that size feel the need to do that? Maybe there was something more dangerous there and we haven't found it yet.
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Old June 22nd, 2014, 02:11 PM   #57

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It could have been for cooling. The wet sail would leach heat from the body if there was a breeze, as there usually is at dawn and dusk on a shore.
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Old June 22nd, 2014, 02:14 PM   #58

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It could have been for cooling. The wet sail would leach heat from the body if there was a breeze, as there usually is at dawn and dusk on a shore.
Or it could catch heat if it was too cool... Though given the general theory that theropods were warm blooded, the purpose of the sail on Spinosaurus is not fully known. Theories range from temperature regulation to some form of sexual display.
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Old June 22nd, 2014, 02:16 PM   #59
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It could have been for cooling. The wet sail would leach heat from the body if there was a breeze, as there usually is at dawn and dusk on a shore.
Indeed and may have been used to heat it up as well given the fact they were cold blooded..or were they?
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Old June 22nd, 2014, 02:39 PM   #60

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Most of the big sea-going monsters were aquatic reptiles, IIRC.

And yes, a dry sail would absorb heat, a wet one would lose heat.
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