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Extinct Animal Questions
Topic Started: Nov 26 2013, 10:24 PM (193,232 Views)
Posted Image Flish
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http://markwitton-com.blogspot.com/2017/06/revenge-of-scaly-tyrannosaurus.html

Naming you a terrestrial animal over three tons is already a difficult task, there's literally three of them. Two of them are elephants, which are a bad example because they're incredibly compact in build, and the third is a rhinoceros, which is also compact in build and covered in armor. Plus, none of them are mesotherms like Dinosaurs.

Including semi-aquatic animals, we add a whopping one (the southern elephant seal) which has a fur coat and a thick layer of blubber. That said it is native to a colder habitat than the vast majority of Dinosaurs, but it also of course has a higher body temperature.

If we include extinct animals we know the integument of, we get the woolly rhino and woolly mammoth, which both had a thick coat of fur. They did live in polar conditions, importantly, though.

but yeah, you can't because our sample size isn't large and none of them are built anything like a theropod. African elephants are from a similar environment to Therizinosaurus and Deinocheirus, but they're elephants still aren't mesotherms and still are just about as compact of a mammal as you can get.
Edited by Flish, Jan 1 2018, 09:20 PM.
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Six Foot Turkey
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magpiealamode
Jan 1 2018, 08:50 PM
Can you link the post by Witton?

Regardless, it makes sense to me. If the three-ton rule is what I think it is, I buy it--name me an animal today that is over three tons and has a coat of some sort.
The extinct Megatherium weighed in at around 4 tons and in lived in semiarid, arid, and temperate environments. We know from Mylodon that giant sloths were covered in coats of fur.
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Six Foot Turkey
Jan 2 2018, 12:20 AM
magpiealamode
Jan 1 2018, 08:50 PM
Can you link the post by Witton?

Regardless, it makes sense to me. If the three-ton rule is what I think it is, I buy it--name me an animal today that is over three tons and has a coat of some sort.
The extinct Megatherium weighed in at around 4 tons and in lived in semiarid, arid, and temperate environments. We know from Mylodon that giant sloths were covered in coats of fur.
That reasoning doesn't make sense here, given what we're arguing. Mylodon only weighed about 1 metric tonne- well within the suggested "furry" range. We have nothing from Megatherium itself. It could well have been naked or sparsely haired. After all, Ground Sloths are built more or less like elephants, with squat limbs and bulky torsos.

Do we know anything about Ground Sloth metabolism? If so, how would it affect this debate?
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stargatedalek
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I'm not slow! That's just my moe!

I should point out that the partial loss of feathers in ostriches is also not a valid reference since ostriches are adapted to lose heat quickly in compensation for running long periods at high speed. Their range also includes areas far more arid than any of the dinosaurs in question.

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babehunter1324
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magpiealamode
Jan 1 2018, 08:50 PM
Can you link the post by Witton?

Regardless, it makes sense to me. If the three-ton rule is what I think it is, I buy it--name me an animal today that is over three tons and has a coat of some sort.
Behold the hairless Woolly Mammoth!!

(I know, seasonal temperature below - 40°C, but still).

(Also I know it's not extant, but in a geological context it became extinct like an hour ago).
Edited by babehunter1324, Jan 2 2018, 05:04 AM.
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Tunes
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Did Velociraptor and other mongolian animals lived in cold deserts?
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stargatedalek
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I'm not slow! That's just my moe!

Tunes
Jan 2 2018, 12:15 PM
Did Velociraptor and other mongolian animals lived in cold deserts?
All deserts are cold at night.
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magpiealamode
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No good hero is a one-trick phony.

Don't you think he meant cold desert as in the biome? If I remember correctly there are cold deserts in Central Asia, but probably not during the Cretaceous, so it's a no from me.

And yes, I forgot about mammoths and sloths because I wasn't thinking back to a geological hour ago. But yeah if we consider that mammoths lived during an ice age and dinosaurs lived when it was warmer on average than it is today, I think it's fair to say that the three-ton rule could, by and large, hold true with some exceptions. Honestly though, we haven't found enough evidence--parsimoniously, it makes sense to give T. rex feathers, but we've discovered several skin patches and none have them. Maybe certain body parts are more likely to leave impressions than others but statistically, shouldn't we have something by now?

I'm currently in favor of the "bare save for a few wispy patches here and there" model for T. rex and other similarly sized dinosaurs.

Also, Flish--you state that dinosaurs are mesotherms with certainty, but I have literally never heard this. Can I get a source for that?
Edited by magpiealamode, Jan 2 2018, 02:20 PM.
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So wikipedia says that Anteosaurus had weak limbs and was thus likely aquatic. I don't really believe that, since its sister taxon Titanophoneus had long, strong limbs. Does anyone have a good skeletal diagram (or even just a photograph of the skeleton) for Anteosaurus so I can confirm my suspicions? Everything I can find is Titanophoneus.
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Posted Image Flish
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magpiealamode
Jan 2 2018, 02:07 PM
And yes, I forgot about mammoths and sloths because I wasn't thinking back to a geological hour ago. But yeah if we consider that mammoths lived during an ice age and dinosaurs lived when it was warmer on average than it is today, I think it's fair to say that the three-ton rule could, by and large, hold true with some exceptions. Honestly though, we haven't found enough evidence--parsimoniously, it makes sense to give T. rex feathers, but we've discovered several skin patches and none have them. Maybe certain body parts are more likely to leave impressions than others but statistically, shouldn't we have something by now?

I'm currently in favor of the "bare save for a few wispy patches here and there" model for T. rex and other similarly sized dinosaurs.

Also, Flish--you state that dinosaurs are mesotherms with certainty, but I have literally never heard this. Can I get a source for that?
The mesotherm wikipedia page literally has a section specifically on how Dinosaurs are considered mesotherms, with measured temperatures indicating a body temperate for theropods of 89 degrees Fahrenheit. It's not 100% certain if they WERE mesotherms, but it's been the leading hypothesis for several years now, and I'm pretty sure there was a topic on it here. Notably, sauropods have a higher body temperature almost identical to a human's at 98.6 F, but they're also much larger animals who can maintain a temperature like that simply by being gigantic a lot more easily. It's important to note that the theropod used was an Oviraptorid, so Coelurosaurs, even ones about as close to birds as you can get without being a Paravian, did not have the obscenely high body temperatures of modern birds or even mammals. That said, an Oviraptorid and a Tyrannosaur are very different animals, but they have a lot more in common than a Tyrannosaur and an elephant do.

Quote:
 
That reasoning doesn't make sense here, given what we're arguing. Mylodon only weighed about 1 metric tonne- well within the suggested "furry" range. We have nothing from Megatherium itself. It could well have been naked or sparsely haired. After all, Ground Sloths are built more or less like elephants, with squat limbs and bulky torsos.

Megatherium still was a temperate animal, and considering Mylodon lived in the same environment and was covered in literal wool very comparable to a mammoth, it makes a lot of sense that an animal three times its size would at least have a decent fur coating, even if not wool, per-say. Furthermore, since sloths are mesotherms as well, they are the best example to look at in integument of theropods when it comes to mammals- along with other Xenarthrans, probably on par with birds because birds have such high body temperatures that are going to make them likely have a much lighter integument layer than a Dinosaur of the same size- look at anteaters, giant anteaters are covered in very long and dense fur but still can get cold in a tropical environment. Furthermore, as mesotherms, they are much less effected by temperature fluctuations on their body than true endotherms. the same is likely true of Dinosaurs, though with the weight of some of the very large ones means they probably didn't get effected all that much, or were only mesotherms because of gigantothermy as has been proposed for sauropods.
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Tyranachu
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Nerdasaurus

https://www.washingtonpost.com/news/speaking-of-science/wp/2017/06/06/tyrannosaurus-rex-had-scaly-skin-and-wasnt-covered-in-feathers-a-new-study-says/?utm_term=.d6723acc21b0

I've seen these popping up everywhere lately. Sooo... What is the safest depiction of T. rex? Fluffy or scaly?
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magpiealamode
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No good hero is a one-trick phony.

I think the fluffbro days are over, but I'm down to depict it with patches along the spine, neck, throat, etc. Tough to say as of yet.
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magpiealamode
Jan 5 2018, 01:13 PM
I think the fluffbro days are over, but I'm down to depict it with patches along the spine, neck, throat, etc. Tough to say as of yet.
There's a range of possibilities. The Saurian rex is at the maximum-fluffyness end of the spectrum. It could also have been completely bald. Personally I'm not convinced by the skin data- it's too relegated to certain body parts, too many of them are unpublished and the sample sizes are just way too small.
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stargatedalek
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I'm not slow! That's just my moe!

That study was bull.

- It actually didn't bring any new impressions of Tyrannosaurus* to light, only published opinions on some specimens that were already public knowledge. *It did present some new impressions from IIRC Albertosaurus, but still nothing conclusive whatsoever (said new impressions are also supposedly from the face, bringing their relevance to related species into question in the first place).

- Several of the authors of the paper had previously expressed not only reluctance but active dismay in regards to the idea of feathered Tyrannosaurs. Impressions aside these are the opinions of researchers with clearly established bias, and it is absolutely fair to take their conclusions less objectively because of that. Even if they made effort not to act on those biases that could still effect their final conclusions.

- The authors fail to provide any justification for their choices of where to place the impressions on the animals body. A great many taphonomic processes can move dermal surfaces after death (or even after preservation) and the authors don't even attempt to address any of them. If these impressions were much larger or clearly impressions of specific anatomical features than sure we can say with some certainty, but there is absolutely nothing to justify their claims that these several centimeter diameter sections of tissue are from one place and not another.

I will also add that the places they choose (and yes, I do feel we can say it was choice) are places that A) previous interpretations of these impressions did not use, and B) are placed centrally to where most reconstructions place the animals feathers. Yes this is hearsay, but I think it's a valid criticism.

- The impressions themselves are irregular in size and pattern, not comparable to any other scales we know of. Other ornithodiran scale impressions tend to be extremely rich in pattern, but even in reptiles no such random scalation is known. Similarly random surface impressions however can be observed in desiccated skin, and in the exposed skin of some birds. While it's not impossible that these impressions are scales that isn't the most likely conclusion.
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stargatedalek
Jan 5 2018, 04:16 PM
- The impressions themselves are irregular in size and pattern, not comparable to any other scales we know of. Other ornithodiran scale impressions tend to be extremely rich in pattern, but even in reptiles no such random scalation is known. Similarly random surface impressions however can be observed in desiccated skin, and in the exposed skin of some birds. While it's not impossible that these impressions are scales that isn't the most likely conclusion.
That was my conclusion, too. I saw a cast of the Wyrex skin impression at the Black Hills Institute, and it didn't look anything like scales to me- much more like the kind of wrinkled skin you find on elephants or cassowary necks.
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