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Post by Ceratodromeus on Jan 29, 2020 10:27:12 GMT 5
I have gone down quite the rabbit hole regarding Quinkana fortirostrum, can any one help me figure out the body size of this animal? i am cautious about accepting the 6-7m figure that was supposedly figured in Molnar's book on Megalania. From a different thread: I found the description paper of Quinkana fortirostrum ⇾ journals.australianmuseum.net.au/Uploads/Journals/17568/198_complete.pdf{2}
Well, a more detailed description than Molnar (1977) {1}, that is. Here is a comparison with a saltwater crocodile from Molnar(1977) That appears to be a young saltwater crocodile in the comparison, so do what you will with that. I am not well versed enough to scale and measure from images yet. Scale bar = 5cm in all images.
More references{1} Molnar, R.E. 1977. Crocodile with laterally compressed snout: first find in Australia. Science,197:62-64 {2} Molnar, R.E.1982. Pleistocene ziphodont crocodilians of Queensland, Records of the Australian Museum 33(19): 803-834, October 1981. (Published January 1982)
I also came across the description of Q.babarra in an attempt to better understand the size of fortirostrum, but this hasn't helped much, as it is also not known from a lot of material. Anyways, a commonly cited figure of 3m for babarra is floating around, and the holotype for this species is only noted to be "slightly smaller than the holotype for fortirostrum, and i am incredibly confused as to how they got an animal twice the length from this , or how they got it at all.
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Post by Infinity Blade on Jan 29, 2020 17:17:32 GMT 5
I think blaze might have said something regarding Quinkana's size a while back, but I'd have to do some digging just to find it. I also don't remember if what he said is anything new to what you have here.
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Post by Ceratodromeus on Jan 30, 2020 0:45:20 GMT 5
I think blaze might have said something regarding Quinkana's size a while back, but I'd have to do some digging just to find it. I also don't remember if what he said is anything new to what you have here. I thought so too, but the only thing i can find on Quinkana here is the thread in the sympatric section, in which theropod mentions a jaw fragment suggesting ~6m, but that is extraordinarily dubious for me to find right now. Down the rabbit hole i go..
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Post by Infinity Blade on May 22, 2020 6:10:30 GMT 5
Do scientists nowadays use Neornithes as the clade name for crown birds? Or is Neornithes just thought of as a junior synonym for Aves? I looked at Wikipedia's article on birds, and it seems to suggest the latter, but from experience I can't trust Wikipedia a whole lot on this. en.wikipedia.org/wiki/Bird
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Post by theropod on May 24, 2020 0:08:10 GMT 5
Well in all honesty I get the impression that even ornithologists and dinosaur palaeontologists are totally confused on what clade "Aves" is actually supposed to refer to. One lecturer in ornithology suggested that all sauropsids should be called "Aves", as the name takes nomenclatural precedence over Reptilia/Sauropsida and a group not including birds wouldn’t be monophyletic. Which is technically correct, though I don’t understand his reasoning for insisting Aves must be so inclusive, which just seems completely arbitrary to me (especially next to including only the actual stem-lineage up to the split with crocodiles, i.e. Avemetatarsalia). Aves as traditionally used was monophyletic already (whether it’s just Neornithes or Neornithes + part of the way down the stem), and whatever it is, it definitely never included crocodiles, lepidosaurs or turtles, which are all extant and therefore crown-groups of their own that would have "equal rights" to Aves. Just naming an entire clade after the oldest crown group of that clade would be a weird practice. Also that would throw up the problem that we’d have to call amniotes as a whole either "Mammalia" or "Aves", as both were named at the same time but predate "Amniota" by a century. Ok, enough of that, sorry.
So no, I don’t think there is anything like a consensus on using "Aves" to refer to only crown group birds. Better use Neornithes, which everyone is agreed on the meaning of.
I think with Avialae, it is generally agreed that it should include stem-group birds up to a certain cutoff point, though where exactly that cutoff is supposed to be is not really clear (it definitely doesn’t include all Avemetatarsalia in common usage either, more like everything closer to Neornithes than to core Deinonychosaurs). I think that clade is potentially still of use, but before using it in a paper I’d have to decide what definition is the most sensible and widespread.
Aves really doesn’t seem to be used all that much outside of exclusively neontological circles to be honest (i.e. circles where it doesn’t matter because there’s only the crown groups to worry about). At this point, it’s more like "Plantae" or "Animalia" in that it refers to organisms that fall into a certain field of study (botany, zoology, ornithology) more than to a concrete clade (which in these would be Streptophytes or at least Chlorophytes or Diaphoretickes, Metazoa and Neornithes or at least Avialae).
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all
Junior Member
Posts: 238
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Post by all on May 31, 2020 23:38:51 GMT 5
Xylomannan is a protein that attaches itself with help of certain oil to cell membrane of Alaskan darkling beetle to prevent ice to enter the cells when its really cold. this type of beetle can survive temperatures of - 60 degrees Celsius. Alaskan red flat bark beetle can survive temperatures of -150 degrees Celsius. What kind of protein does Alaskan red flat bark beetle use to keep from freezing and does it have same principle of action as xylomonnan? I know this is asking for a lot but if you could point me in right direction I would appreciate it.
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Post by jhg on Jun 18, 2020 4:43:15 GMT 5
I would assume it's a similar substance. I admit I don't know arthropods very well. Why didn't Yugoslavia ever consider an alliance with China after the Sino-Soviet split?
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Post by Infinity Blade on Jul 31, 2020 2:15:34 GMT 5
How much O 2 is in the stratosphere? I understand that O 3 exists in that layer in such high concentrations that it's toxic, and the air is too thin for normal breathing, but how much breathable O 2 are we talking about here? www.ccpo.odu.edu/SEES/ozone/class/Chap_6/6_2.htmEDIT: I found a paper. sci-hub.tw/10.1038/138544a0It seems oxygen percentage is similar to that of Earth's surface. Air being "too thin" didn't mean what I thought it meant; you can't breathe there because oxygen is less compressed. So while the percentage of oxygen is similar as on Earth's surface, there's less oxygen to breathe.
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Post by theropod on Jul 31, 2020 19:42:32 GMT 5
That’s the significance of partial pressure vs concentration. The concentration of oxygen up on mt. Everest is the same as down here. But there’s much less air overall that the partial pressure is lower.
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Post by Infinity Blade on Aug 7, 2020 9:00:05 GMT 5
In Predatory Dinosaurs of the World, Greg Paul mentions the theory of elastic similarity. He says that when length is doubled in an elastically similar structure, its diameter needs to increase nearly three-fold (2.83-fold, to be more precise) in order to maintain the same resistance to bending. This was written all the way back in 1988, and I don't know if anything has changed since then, so I have to ask: does this still hold true?
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Post by creature386 on Aug 7, 2020 12:11:36 GMT 5
From mathematical principles, this seems very sound, actually. We do know that doubling the length causes an eightfold incease in mass. Since bending resistance (as described by Paul) scales with the square diameter, the bone's diameter would need to increase by the square root of eight (which is roughly 2.8).
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Post by Infinity Blade on Aug 7, 2020 20:06:28 GMT 5
Okay, I deleted the subsequent posts now that your edit has been made clear. Yeah, that makes more sense.
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Post by Infinity Blade on Nov 28, 2020 6:03:46 GMT 5
Everyone knows that carbon-14 dating isn't accurate for things older than 50,000 years old (occasionally 75,000 years old with special preparations). But I've known for a while now that it also isn't accurate for things younger than 100 years old (and shockingly, there are dating methods for things younger than that). Can someone explain why this is the case?
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Post by creature386 on Nov 28, 2020 14:28:03 GMT 5
It's been a while since I concerned myself with isotopic dating. My guess would be that you need a high enough number of daughter isotopes to receive meaningful results. A thousand years might be too little for enough N-14 to form. If you have too few daughter isotopes, it can be harder to rule out contamination (there's also the issue that radioactive decay is a stochastic process which in and of itself necessitates a certain sample size).
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Post by Infinity Blade on Feb 1, 2021 6:22:52 GMT 5
If Lystrosaurus were alive at the end of the Cretaceous, could it have survived the K-Pg event? I know the P-T extinction event was far more severe (with regards to how much life it killed off), but I get the impression that the P-T event was just a little more lenient on large terrestrial animals than the K-Pg event was. Not only did Lystrosaurus survive (although, it seems larger species went extinct), but even the apex predatory Moschorhinus survived (which was supposedly 1.5 meters long). So I'm wondering if it could survive a mass extinction that was entirely different in its cause.
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