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Post by Infinity Blade on Nov 25, 2019 7:19:35 GMT 5
That is what I meant, but please understand that this isn’t my field of expertise, and so I wasn’t sure if that’s how it actually works. This is why I only asked instead of outright assuming it was (which, had I done so, would have myself look even dumber).
Anyway, your method does indeed sound more reasonable (although it would be nice to know if there's anything more to it). From this I gather that it depends on where on the horn's length we're talking about (the bony core will taper to a point and there be a point where the horn's cross section is just keratin, particularly at the distal end).
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Post by theropod on Nov 25, 2019 14:14:58 GMT 5
Hmm whether you calculate the strength of the keratin and the bone separately and then add them up, or calculate the average strength properties according to the percentage of area made up by keratin will give you the same result.
Say bone has a strength of 100 and keratin of 50, and the cross-section is 50% bone. Then the strength would be 50*.5+100+.5=(50+75)/2*1
From my understanding, this is indeed the proper way of calculating it, sum up the strength of the individual components.
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Post by Verdugo on Nov 25, 2019 17:25:40 GMT 5
That is what I meant, but please understand that this isn’t my field of expertise, and so I wasn’t sure if that’s how it actually works. This is why I only asked instead of outright assuming it was (which, had I done so, would have myself look even dumber). No worries mate. I do not judge. I was just a bit unsure and confused of not knowing what you actually meant when you said so. Anyway... You meant like an explanation of how i came up with that or something else? As you probably already knew, MPa is basically Force per Surface Area (you can actually convert it to N/mm^2, which does make it more comprehensible, at least to me). So the Strength you're looking at is basically 'lb 4 lb' Strength. For instance, why Bones are stronger than Keratin in its lb 4 lb Strength (according to your post), it would not really matter if says, the Keratin structure is 10x as thick as the Bone structure. So if you want to compare two animals to see which one has stronger Horns/Tusks, you'll need to take the 'lb 4 lb' Strength value and times it to the Cross-sectional area of the Horn to work out how strong the Horns are in absolute term (lb 4 lb Strength will not be sufficient if one animal has thicker horns than the other). For instance, if an animal has horn made out of keratin, tensile Strength is 100 MPa (or 100 N/mm^2), the cross sectional area of the horn is 100 mm^2, then the Strength in absolute term is: 100 * 100 = 10000 N So the Horn would take 10 kN of Force to break under Tensile stress. Maybe you could just take the part right at the middle of the horns and assume 50% Keratin 50% Bone for the sake of simplicity? AFAIK, the way how Keratin sheath and Bony core are related to each other is not uniform. Some animals have small Bony core but large Keratin sheath so there horns at midpoint would be pretty much all Keratin. According to Mark Witton, old Triceratops appears to shrunken its Bony core so in old Trike, the horn would be mostly Keratin while in younger Trike, there would be more Bones  |
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Post by Infinity Blade on Dec 6, 2019 4:49:11 GMT 5
Does anyone know why suboscines are called the Tyranni? I know it's derived from the type genus, Tyrannus, but...why is it called Tyrannus? What about the bird compels one to call it a "tyrant"?
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Post by theropod on Dec 7, 2019 22:28:29 GMT 5
Regarding Tyrannus tyrannus, it is hard to imagine what must have been going on in Linnaeus’ head when he named it… Yes, what's more, humans(of course, talking about the physical potential of a fit, trained runner, not the average overweight couch potato) are actually in the very top tier of long distance runners. The few animals capable of keeping up with the best ultra runners would possibly belong to wolves, sleigh dogs and some ungulates. Ostriches. My lecturer in respiratory physiology seemed of the opinion that there was not much else that could match a human in endurance. Things like wolves, horses and pronghorn are amazing mid-distance runners (and obviously vastly faster than humans over those distances), but even they seem unable to match humans when it comes to running for several hours (hence why San hunters can chase down a kudu even though the kudu can outspeed them with contemptuous ease). This makes me wonder though, is there any basis for the commonly cited claim that bipedal locomotion is more efficient for endurance running than quadrupedal locomotion? |
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Post by Infinity Blade on Dec 7, 2019 23:09:27 GMT 5
Okay, I asked people on Discord, and apparently ‘tyrant’ back in the day (18th century) just mean king or ruler, with its negative connotations being much more recent cultural norms, so calling it a ‘tyrant’ inasmuch as it is a king (kingbird) would fit. And some have noted the aggression and territoriality of these birds, maybe like what you’d expect of a tyrant ruling over his/her land.
I’ll try to find something over bipedal vs quadrupedal energetics later.
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Post by sam1 on Dec 8, 2019 0:10:54 GMT 5
Regarding Tyrannus tyrannus, it is hard to imagine what must have been going on in Linnaeus’ head when he named it… Yes, what's more, humans(of course, talking about the physical potential of a fit, trained runner, not the average overweight couch potato) are actually in the very top tier of long distance runners. The few animals capable of keeping up with the best ultra runners would possibly belong to wolves, sleigh dogs and some ungulates. Ostriches. My lecturer in respiratory physiology seemed of the opinion that there was not much else that could match a human in endurance. Things like wolves, horses and pronghorn are amazing mid-distance runners (and obviously vastly faster than humans over those distances), but even they seem unable to match humans when it comes to running for several hours (hence why San hunters can chase down a kudu even though the kudu can outspeed them with contemptuous ease). This makes me wonder though, is there any basis for the commonly cited claim that bipedal locomotion is more efficient for endurance running than quadrupedal locomotion? Yeah, good point. Forgot about the ostrich. Well, from a biomechanical standpoint it looks kinda obvious that two legs require less energy than four(overall, even accounting for the increased stride frequency). Humans aren't the best examples with their multifunctional anatomy and dexterity but when it comes to efficient running I think there's no beating a highly optimised bipedal bird/dinosaur. Or a kangaroo? Some good little pieces on the subject. www.popularmechanics.com/adventure/sports/g418/animal-kingdom-top-marathon-runners/www.google.com/amp/s/www.orlandosentinel.com/news/os-xpm-1986-01-19-0190220124-story,amp.html |
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Post by theropod on Dec 8, 2019 1:10:53 GMT 5
In the case of dinosaurs, they have the added advantage of a far more efficient respiratory system than mammals, but I was wondering how much of their stamina (in the limited number of examples of cursorial birds that we have) is simply down to bipedalism.
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Post by Infinity Blade on Dec 25, 2019 18:12:54 GMT 5
I've recently been rewatching Walking with Dinosaurs, and I've been curious about something. Which species from Time of the Titans (episode 2) would still have been alive by the time of Cruel Sea (episode 3)? Do we even have clear enough "resolution" into what went extinct and what was still around after a 3 million year time gap so long ago?
If I take Wikipedia's temporal ranges for certain animals at face value, Allosaurus would still have been around, but Stegosaurus and Diplodocus would have gone extinct by Cruel Sea. I'm not sure if these are actual known ranges of time in which these genera lived or if these are just ballpark estimates for known specimens (in which full temporal range is unknown).
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Post by creature386 on Dec 25, 2019 19:02:00 GMT 5
I cannot tell you more than Wikipedia does, but I can answer your question on stratigraphic resolution. Generally, we can perform biozonation for the Phanerozoic at a resolution of 2-3 million years. Here's what my textbook on biostratigraphy says (don't have a link, sorry):
Plankton Stratigraphy by Bolli et al. 1985 has been cited as an example of detailed biostratigraphic donation for the Mesozoic and Cenozoic. If you don't have such a table at hand, you can just grab a generic stratigraphic table and look for where the borders between geologic ages lie. Our records are precise enough to tell that something changed at these borders. Cruel Sea took place in the Tithonian. Time of Titans likely took place in the Kimmeridgian. When people tell you that one animal lived in one age and not in the other and they have data to back it up, you can probably believe them.
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Post by Infinity Blade on Dec 25, 2019 20:36:20 GMT 5
Interesting! I didn't really know about the use of plankton for biozonation down to just a few million years.
I guess it's just a matter of who has data on exactly what time intervals (down to a million years) these animals are found in.
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Post by creature386 on Dec 25, 2019 20:50:12 GMT 5
Note that this probably only applies to marine sediments though. "Calcareous nannoplankton" in practice means "coccolithophores" (and a bunch of other exclusively marine groups) and "planktonic foraminifers" means "Globigerinina". Neither of these occur in fresh water where dinosaurs are typically deposited. Still, looking at geologic ages/chronostratigraphic stages should give you a good minimum resolution quality.
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Post by Infinity Blade on Jan 9, 2020 10:13:00 GMT 5
Can anyone find me information on how flexible an elephant's neck is? I tried searching before and just recently (though more thoroughly the first time) and all I could find on the matter dates back to the early to mid 19th century. Does anyone have any more up to date work, or even quantitative data, on the flexibility of an elephant's neck (in all planes)? The old sources I mention seem to suggest the elephant's short neck is inflexible, but is made up for by the length and flexibility of the proboscis. While this intuitively makes sense, I just want to make sure. Edit: once again my research ends up answering my own question. link |
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Post by Infinity Blade on Jan 20, 2020 9:21:46 GMT 5
This might be a stupid question, but does the term "order of magnitude" only refer to when a number is strictly 10, 100, or so on times greater than another? Or can it be applied more broadly, as in, simply having one more digit? Obviously 100 is an order of magnitude greater than 10. But is 2,500 considered two orders of magnitude greater than 32? Is 10,000 one order of magnitude greater than 6,000?
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Post by creature386 on Jan 20, 2020 13:33:09 GMT 5
On a phone, so I can't give you an in-depth answer. The term “order of magnitude“ has a clear mathematical definition. en.m.wikipedia.org/wiki/Order_of_magnitudeLook at the equation and table under “Definition“ to see how it applies to numbers which aren't multiples of ten. |
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