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Extinct Animal Questions
Topic Started: Nov 26 2013, 10:24 PM (193,226 Views)
Furka
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Not exactly an extinct animals related question but it came to my mind when thinking of Oviraptor, would it actually be possible for a large vertebrate like that to feed largely on eggs ? (assuming it lived in an environment where eggs were available all year round and not as a seasonal resource).
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stargatedalek
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I'm not slow! That's just my moe!

Furka
Feb 27 2018, 11:34 AM
Not exactly an extinct animals related question but it came to my mind when thinking of Oviraptor, would it actually be possible for a large vertebrate like that to feed largely on eggs ? (assuming it lived in an environment where eggs were available all year round and not as a seasonal resource).
Doubtful, it would need to travel so extensively that would be impractical.
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magpiealamode
Feb 27 2018, 09:12 AM
I don't think I mentioned ceratopsian color once and afaik there is no evidence of it so I am gonna call that a moot point for now. This isn't about hiding, anyway; I did say that they were too big for that, so let's stop talking about camouflage because I think we all agree. I also never said I thought female ceratopsians would be drab. Regardless, I think ducks are kind of a bad example. Peafowl works much better, as both sexes are colorful but males are much more so.
Right now I'm talking about structural characteristics such as size, ornamentation, and weaponry. Danny already made some important points: increasing these things has a cost and animals won't do it unless there is some benefit. Obviously, protection is one reason for size, as are a few other things. Beyond that however, sexual selection plays into it. Sexual selection may have gone with color, and it's possible then that we will find no obvious evidence of sexual dimorphism. However, perhaps it went with things like horns, muscular strength, or frill size--a species that keeps harems and/or competes with for mates would select for these things, as the biggest, strongest individual would be the one with the most chances for mating and the highest fitness. However, the non-competitive sex wouldn't maximize this stuff as it could be too costly to be useful.
But that's not how it works. It's not an either or thing, clearly, and the peafowl you keep coming back to show just that- even with a gigantic train the males are colorful and use intraspecific combat (they have giant spurs for a reason). Many antelope again have all three. Peafowl are actually a bad example in your case because they show just how sexual selection works- in Blue peafowl, where they live in sparse forests or grassland environments, the females are much drabber because hiding them and their young is much harder. Yet in the jungle dwelling green peafowl, both are nearly identical except for the male's train because she can hide way easier so she gets to be more colorful. It's not a "oh this gender gets to fight so they get to be colorful/have bigger ornamentation" case because if it was almost every animal would be like this- but in animals where neither gender has to hide, but they have great color vision, they're usually almost identical. Jacanas only show size dimorphism and this can easily be explained in that the males carry the young around so they have to be smaller to carry them without sinking. almost all seabirds, who have few if any predators (or only marine based ones) are almost impossible to tell apart.

Rhinos and Elephants are a poor example because they're colorblind and have pretty bad eyesight, must travel long distances to find mates, and also put way more energy into one baby than a similar sized dinosaur, so being colorful is out the window and they must rely on scent (which is what they mostly do) and significant physical differences to tell each other apart- and it just so happens the males are the ones who fight over females so this is why we see it being horns and tusks.

Finally, there seems to be this strange opinion that it's one sex choosing the other when it's really not. It's usually either they both pick each other (though males are often less picky, though this is because they have far less to loose in mating with a "bad" female) or the male forces themself on the female.

And of course female ceratopsians will have some very minor sexual dimorphism- but the whole argument was on if Machairoceratops and Diabloceratops would be potentially the same species but just different sexes, and really the chances of that are very slim because any amount of sexual dimorphism you'd see would probably not be in the display structures or weaponry but in size or some minor body proportion differences such as hip width (though in Ceratopsians, I doubt their hips were ever an issue for laying eggs) because both sexes are showing off how fit they are, not just the males.

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stargatedalek
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I'm not slow! That's just my moe!

Aside from Triceratops itself most ceratopsians "weaponry" wouldn't be useful for defense or combat at all. They didn't have specialized horns or frills for combat because they were structures that evolved for display and for nothing else, which is why they should not be dimorphic like elephants and such.
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Ulquiorra
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stargatedalek
Feb 27 2018, 01:12 AM
magpiealamode
Feb 26 2018, 11:17 PM
I'm not sure you're understanding the meaning of sexual selection, and if you are it's not coming through to me. Sexual selection specifically operates via sexual attraction; it's not just normal selection that happens to apply to one sex or the other. Sex selection is not what makes female ducks drab, it's what makes male ducks colorful. In no way is a female duck sacrificing anything to be inconspicuous, she is only making herself harder to detect and increasing her fitness, and if you haven't noticed, drakes are kind of sex machines so I don't think attraction is an issue.
If as you claim it was the male duck making the sacrifice to be colourful, than the females should be choosing the male.

Male ducks will just take whatever females they want, they don't have the ability to choose their mates, so why would male ducks be more colourful if that wasn't the default?

Colour serves a great many functions besides sexual selection, and pretty much every non-mammalian animal that doesn't spend extended periods of time guarding or hiding young has some degree of display colouration.

You are misinterpreting the entire concept.
Not to mention drakes, outside the breeding season, go through an eclipse phase. During which, their plumage is more or less identical to that of the females.

If Dinosaurs had any form of dimorphism, would it be seasonal like that of ducks?
Edited by Ulquiorra, Feb 27 2018, 04:51 PM.
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caviar
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stargatedalek
Feb 27 2018, 01:12 AM
magpiealamode
Feb 26 2018, 11:17 PM
I'm not sure you're understanding the meaning of sexual selection, and if you are it's not coming through to me. Sexual selection specifically operates via sexual attraction; it's not just normal selection that happens to apply to one sex or the other. Sex selection is not what makes female ducks drab, it's what makes male ducks colorful. In no way is a female duck sacrificing anything to be inconspicuous, she is only making herself harder to detect and increasing her fitness, and if you haven't noticed, drakes are kind of sex machines so I don't think attraction is an issue.
If as you claim it was the male duck making the sacrifice to be colourful, than the females should be choosing the male.

Male ducks will just take whatever females they want, they don't have the ability to choose their mates, so why would male ducks be more colourful if that wasn't the default?

Colour serves a great many functions besides sexual selection, and pretty much every non-mammalian animal that doesn't spend extended periods of time guarding or hiding young has some degree of display colouration.

You are misinterpreting the entire concept.
Only that it is the female that makes the choice.

You see female ducks have a very intricate cloaca to avoid coercion from frustrated males who just want to get laid with any female duck.

She will just close her cloaca and make it almost imposible for males to fertilize her eggs, only the mate whom she aproves as the father of her chicks is allowed to penetrate her labyrinth cloaca.

@Flish: Your whole argumet about sexual selection is a bit close minded, sexual selection can work in many, many many, many, many ways, just narrowing it to females get to be drab in order to survive, completely ignore the fact that it's them the one who chooses their mates, it the girls who have the ability and the necesity to choose the best mates to be father of their children.

Remember eggs are more expensive to produce that sperm, so it is them, the femalse who cannot give their eggs to a random male, whom they didn't choose.

So a female do not get drab in order to survive, it's the other way around, the males get colorful in order to be the ones that females favor. Novel signals work because of this, females are bound to choose any novel character that other males do not have be it a patch of color or a different song than the rest of the males.

Both sexes being colorful is a completely misunderstandig of how sexual selection works, females don't get colorful because the males do not choose them. Look at phalaropes for example, it's the girls who dance and seduce the males, so they are the ones who are colorful.
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It's not close-minded, it's literally observable throughout the animal kingdom to be the case. If the female does not have to hide to protect her young, she is not any less colorful than the males. The phalaropes are an excellent example of this and prove my point, so thank you for bringing them up. The females are the ones who go off and let the male watch over the young, so the males are drab to hide themselves instead. If it was the other way around, seabirds, jacanas, parrots, turtles, and the many, many ridiculously colored reef fish would not be colorful. In fact, if you look at the bird groups where both parents watch over the young, you get birds that are very difficult to tell apart, even if they are colorful. Female macaws aren't brown, and swans are also practically identical.

You can't just look at much smaller birds where one gender watches over the eggs and use them as an example in this case because their behavior is going to be about as far from any large herbivorous Dinosaur as you can get. The best examples are going to be fish and turtles. Female turtles are almost always larger than males, but this is probably because they are making massive egg clutches for their size almost constantly (Turtles love to... do things) and thus need larger energy reserves. The amount of fish you can actually tell the difference in sex of is absurdly small, and is almost always because of intraspecific competition when you can. Yet here we are, with these thousands of reef fish that are are bright blue and yellow, purple, black and white, etc. yet using your logic they should all be brown because they neither sex has to compete the other at all (typically they have mass spawnings. There are exceptions but those ones also show next to no sexual dimorphism).

So, because literally every other group of herbivorous animals that does not have to hide while watching over young and has good color vision is colorful in both males and females, I think it's safe to say that Dinosaurs would be the same. You're not going to be seeing sexually dimorphic ceratopsians very often if at all just like you don't see sexually dimorphic tangs or box turtles.

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magpiealamode
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No good hero is a one-trick phony.

Obviously, not every animal that is colorful was sexually selected--poison dart frogs, for example. Green peafowl have to hide of course, they just are able to do so while being a verdant green--but the male train is a sexually selected trait that proves to females he is a good mate. You told me something confusing, which is that my peafowl example was bad because it showcased sex selection, then you proceeded to explain how natural, not sexual, selection operates in the species. I'm going to keep beating this drum, sex selection has nothing to do with making females drab, that's natural selection's job. Sex selection makes males (and maybe females) colorful, or otherwise possessing some exaggerated feature. In some animals where both sexes are colorful, such as green peafowl, sex selection probably has a hand in at least some of it, but it's natural selection which allows it to stay. If you moved green peafowl to a brushy environment, the females would become drab because the bright ones would be more likely to get eaten. The males would be pushed in this direction, except that the more vibrant ones are going to have more children. If they can escape predation, they will stay colorful. There is a difference between natural and sexual selection and I don't think you're seeing it.
Sex selection could increase frill size and ornamentation in male ceratopsians, maybe not because they are the most weaponized, but because those individuals will be most intimidating to rivals and most attractive to females. It's very simple.
Ultimately, it comes down to a species' mating system. You've chosen seabirds as an example of a non-dimorphic sex. Of course they're not dimorphic, they pick their mate through a ritual once and stick together for life. In harem keeping species, such as elk or elephant seals, the males are bigger, more muscular, and have greater weaponry in order to defend their claim. In species such as birds of paradise or grouse, each male still tries for multiple mates, but doesn't claim them, meaning he has to be attractive to as many females as possible. That's why they've developed such amazing colors and ornamentation. There are multiple mechanisms for sex selection. Each species has a particular method of attraction--some go for ritual, some go for displays, some for combat, etc etc with some mixing. If ceratopsians are monogamous maters-for-life, there will be little dimorphism. If they are harem keepers, the males will likely display increased size and strength for the purposes of intimidation and possible combat. If they display and let the females pick, they're going to be more colorful or ornamented, not because the females need to be less colorful, but because sex selection works like an arms race. The attractive features in the sex in question will be amplified until they become detrimental. A particularly gaudy female would probably receive no benefits unless it's a polyandrous or monogamous species, so her getup will stay only as colorful as necessary--and any mutations which might make her more colorful won't be amplified like they will be in males. Both sexes need to show how fit they are. However, depending on the mating system, one will probably need to show it differently.
If we're to prove or debunk sexual dimorphism in ceratopsians, we'd need more fossil evidence, both to observe actual specimens and to work out their mating systems.

Edit: Despite what you may think, phalaropes are just reinforcing this case. The competitive sex becomes more colorful in that example, because the most colorful (attractive) ones get the most matings.
As for reef fish, again. Natural selection allows them to be colorful, in fact may even encourage it because their environment is so colorful. I don't know how all their mating systems work but it probably wouldn't necessitate sexual selection.
Edited by magpiealamode, Feb 28 2018, 12:17 AM.
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I never once said or implied that sexual selection makes females drab- quite the opposite. I simply stated that females are only drab because they have to hide- which is true, and that if they did not have to hide, sexual selection would make them just as colorful and showy as the males because that's what we see in almost every animal group. For some reason there seems to be this thought that sexual selection only exists in one gender when it always exists in both- it's just sometimes more pronounced because of differing lifestyles that require one sex to be less gaudy.

Sexual dimorphism from intraspecific competition (and thus harem-style social groups) is always in animal groups where a lot is put into just a few young- it's important to have a fit and powerful male because he is going to be the one protecting the young and females, and also helping make new young. That's why in elephant seals, for example, the sexual dimorphism is so absurd yet in deer it's rarely much more than the males having antlers and the females not. Ceratopsians, like all dinosaurs, would have had a ton of babies so intraspecific competition and harem breeding is very, very, unlikely. It's not if they're monogamous, it's about how important and how easy it is to raise the young, or if the young are raised at all, that determines this.

Finally, just because the female is not displaying does not mean she won't be just as colorful- Bontebok have the same color patterns in both male and females, and it's certainly not a pattern and coloration picked for being good for hiding. Aposematism also plays into it because showing that she's just as dangerous as a male is important, especially when you can't exactly hide. Unfortunately, our selection of large animals that can't/don't need to hide is limited to mammals, but even among those we can see pandas, anteaters, orcas, many pelagic dolphins, all follow this pattern where they're equally as gaudy regardless of gender even though the males have to get the female's attention, and really if females were drabber just because they didn't display we would see some fossil evidence of this in Dinosaurs- yet we get hundreds of Ornithiscian species where there is no discernible difference between the two sexes from what we can tell. There might be a size one, but we wouldn't be able to tell that easily and as discussed before it's not likely (though not impossible- of all the sexually dimorphic characteristics, size has the most variables effecting it for sure), and then because we see all these display structures, if the two genders were dimorphic, we'd expect the females (or whichever gender is displaying) to lack these structures since, if it really doesn't matter what she looks like, she might as well not waste the energy growing them. So while there is a very small chance that females would be a different color, there is literally no reason for them to be and because of that the chances of them being a different color are much, much smaller.

EDIT: ...That's not how sexual selection works. Again, evolution doesn't go "oh well these males aren't displaying anymore it's the females so guess they are gonna be brown now" it goes "oh well these males are protecting these babies so they can't be colorful anymore." If this was the case, Jacanas, which just like Phalaropes, have the females courting the males, would show the same thing. But they don't, because the males don't have to hide to raise the young. I'm literally saying that in the absence of any pressure that would cause sexual dimorphism, both genders are colorful rather than one just being drabber for no reason. Which is what we see in fish. And turtles. And birds. And the entire animal kingdom. This is why we wouldn't see it in Dinosaurs very often, especially Ceratopsians- there is no reason to be drabber. They're both going to be colorful.
Edited by Flish, Feb 28 2018, 12:55 AM.
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magpiealamode
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No good hero is a one-trick phony.

Quite frankly I'm getting tired of this conversation as it's going nowhere; you've said a lot of things both true and untrue, but your last statement has something at the heart of your argument which is what I really disagree with, so I'm going to address that and then drop it.

Flish
 
I'm literally saying that in the absence of any pressure that would cause sexual dimorphism, both genders are colorful rather than one just being drabber for no reason.


I agree with you, however I have not seen you put fort any examples of one of those pressures besides protecting young, but I'm sure there are many. One that was mentioned was nutrient requirement for growth of extra horns, frills, muscles, size, etc. Also, the difficulty and energy expenditure that would come from hauling all that stuff around. Color is really actually a bit irrelevant, since we don't know (to my knowledge) any ceratopsian colors. But with those expenditures in mind, if only one sex is getting the mating benefits, only that sex will magnify those features, past the point that normal natural selection would allow. If both or neither sex gets the advantage, there will be no difference. So like I said, we need to know the mating system of the species in question. Is it most like that of fish or turtles? Maybe, although it strikes me as a bit of a non sequitur. Whatever, that wasn't exactly my interest here in the first place.
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I'm genuinely confused what you're trying to debate at this point because I never said they couldn't have smaller horns and frills on the female- This is about the only sexual dimorphism we see in fish because it IS a lot of energy to grow a different skull shape or longer fins. There are a lot of pressures, primarily nutrient consumption, that are going to effect this. However, color is a much less resource-expensive thing to develop for both genders, and really the only driving factor that is going to make females duller over their male counterparts is going to be rearing young- except for in harem species, and in this case we can again mostly rule out Ceratopsians since they have so many young for so little resources comparatively. If there were other factors, we'd see significant differences at least in SOME species of fish who perform mass spawns- but we really don't. They're all identical. If there was some natural pressure that would make fish who mass-spawn sexually dimorphic, you'd expect to see it at least in some species, but you don't. The only fish with significant sexual dimorphism are species that pair off.

What I DID say, however, is that if Ceratopsians are going to be sexually dimorphic, as you said, the females are not likely to grow the same crests and horns as the females. But they apparently do or we would have found obviously different genders in Dinosaurs, yet really the only sexual dimorphism in Dinosaurs seen is some sketchy dimorphism in Hesperosaurus, and potentially also male Diplodocus whip-cracking their tails (Causing the last few vertebra to ossify together from damage), though even then neither is definite. This means that if the females are putting the time and energy into growing the same display features as males, they probably are not going to be sexually dimorphic in coloration, either, because they have the exact same display structures and no known pressures causing the females to be duller.

Also, not really related to the debate, but we do know Psittacosaurus sp.'s colors- tan with black spots on the chest, a black face, and light bristles, as far as we can tell. Psittacosaurus lives in a very, very different environment, however.
Edited by Flish, Feb 28 2018, 10:33 AM.
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heliosphoros
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I'm just going to point out that some tetrapods have more than two sexes.
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Incinerox
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Āeksiot Zaldrīzoti

Got a less technical question for you guys:

What popular extinct animals are lacking in good skeletal restorations?
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stargatedalek
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I'm not slow! That's just my moe!

Incinerox
Mar 16 2018, 10:19 AM
Got a less technical question for you guys:

What popular extinct animals are lacking in good skeletal restorations?
Raphus, somehow. There are some good 3D references out there but nothing in a really convenient form.
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Ulquiorra
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What were the "hands" of oviraptorids like?

Were they wing-like, like this?
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Or, three separate fingers, like this?
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