Post ARa7ScOyefpYMYRime by keesey@sauropods.win
(DIR) More posts by keesey@sauropods.win
(DIR) Post #ARZJPP8aWHbMeC3Q3s by john@sauropods.win
2023-01-12T13:41:44Z
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Isn't is just a bit too weird we don't have any cases of really obvious sexual dimorphism in Mesozoic dinosaurs?Or am I out-of-date on that?#dinosaurs
(DIR) Post #ARZLkVDFKMarTjQAHQ by chiasm@mastodon.online
2023-01-12T14:07:56Z
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@john my first thought is they aren't mammals; but tbh I assume lizards are sexually demographic, like frogs are, but they don't carry external gadgets, maybe? Hard to tell by just looking at them?
(DIR) Post #ARZM3VE1VNA71GqQ2S by john@sauropods.win
2023-01-12T14:11:25Z
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@chiasm I was just reading this: https://royalsocietypublishing.org/doi/10.1098/rspb.2013.0401"The extinct giant moa Dinornis is one of the most remarkable known examples of reversed sexual size dimorphism (RSD), with males weighing 34–85 kg, but females weighing up to 240 kg."(!!!)Females were 3-8 times larger than males! They used to be considered different species, and we wouldn't have known any different if we didn't have DNA.
(DIR) Post #ARZMZCOb32Bjt5u6pU by john@sauropods.win
2023-01-12T14:17:08Z
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@chiasm Not digging the terminology "reverse sexual dimorphism" though. There's nothing in the term that suggests males should be bigger than females.
(DIR) Post #ARZOAS7hdVH3KnKVt2 by chiasm@mastodon.online
2023-01-12T14:34:53Z
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@john spiffy!!
(DIR) Post #ARZOwlyl7GI4oeBftY by DreadShips@mastodon.me.uk
2023-01-12T14:43:42Z
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@john Given the presumed difficulty of recognising adults as the same species from the bones alone, I guess it's worth asking what evidence we would need and how likely it is to appear (and what to look for)?Both morphs regularly found in the same bone beds? Intermediate juveniles? Looking for medullary bone in one pseudospecies and never another?
(DIR) Post #ARZPOpiGpIykVNr4lc by john@sauropods.win
2023-01-12T14:48:52Z
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@DreadShips I feel like having a pair of morphs that cannot be ruled out as sexual morphs found in association a few times could be evidence (some dinosaurs are common enough for this to be possible). As far as I know, there's nothing like that.
(DIR) Post #ARZPVo5bGIKLUq5o6i by DreadShips@mastodon.me.uk
2023-01-12T14:44:24Z
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@john I share your feeling of weirdness, btw - surely, surely, surely it was common
(DIR) Post #ARZPVoWtcoA4rUrbea by john@sauropods.win
2023-01-12T14:50:06Z
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@DreadShips Yeah, I think we're missing something. It would be wild if some mesozoic dinosaurs were so wildly sexually dimorphic we wouldn't even consider it!
(DIR) Post #ARZQEnBNTp7jiPFIp6 by chiasm@mastodon.online
2023-01-12T14:58:14Z
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@john Yeah to me sexual dimorphism means the egg/sperm makers are biologically easy to distinguish. I didn't realize it was being used in this case just to refer to *size*. That seems weird.
(DIR) Post #ARZQevVb97sF4FAKFk by john@sauropods.win
2023-01-12T15:02:58Z
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@chiasm Yeah, I really think it should be something along the lines of 'morphological differences between sexes aside from the reproductive system'. Males being bigger than females is just one of dozens of examples.
(DIR) Post #ARZVNoGvIYtZTGxVyq by mike@sauropods.win
2023-01-12T15:55:51Z
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@john The "obvious" sexual dimorphism in extant animals is mostly not in the skeleton, is it? Maybe the dimorphic features just (colours, flaps) don't fossilise well?
(DIR) Post #ARZVQ1JplFcuVyNH2O by mike@sauropods.win
2023-01-12T15:56:21Z
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@john @chiasm This is a nice example, which was new to me.
(DIR) Post #ARZViwvIKRZGNpvFmS by mike@sauropods.win
2023-01-12T15:59:42Z
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@john @DreadShips Someone (I don't remember who) suggested Barosaurus is the male Diplodocus. I think unlikely due to different cervical count, but Apato as male Diplo doesn't seem completely insane. (But how do their stratigraphic and geographical ranges overlap?)
(DIR) Post #ARZWMwpi5CfnggNoO0 by john@sauropods.win
2023-01-12T16:06:53Z
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@mike @DreadShips It's a shame the answer relies on having good knowledge of something as boring as biostratigraphy.We'll never know for sure I guess, but it would great to have a list of co-occurring taxa that can't be ruled out.
(DIR) Post #ARZZtOgSMysZC6DfLE by mike@sauropods.win
2023-01-12T16:46:22Z
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@john @DreadShips I bet John Foster could answer that part. Does anyone know if he's on Mastodon yet?
(DIR) Post #ARZcRfa2FtSJLrgbDc by PeterFalkingham@sauropods.win
2023-01-12T16:20:05Z
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@DreadShips @john even both morphs found evenly in same bed relies on 50:50 sex ratio in life which may well not be the case.
(DIR) Post #ARZcRgDjsHDNL0GJ6W by john@sauropods.win
2023-01-12T17:15:01Z
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@PeterFalkingham @DreadShips If we ever did find that, it would be suggestive though!
(DIR) Post #ARZd9mj92opcG7yzdA by john@sauropods.win
2023-01-12T17:22:57Z
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@mike @DreadShips You should invite him...
(DIR) Post #ARZdOgS4esCX8l6PJ2 by mike@sauropods.win
2023-01-12T17:25:38Z
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@john @DreadShips I invited a lot of dinosaur people during my two-or-three-week cutover period. Not a whole lot of them seem to have come.
(DIR) Post #ARZdrBxj62RMycV8Sm by john@sauropods.win
2023-01-12T17:30:51Z
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@mike It's weird that we had a lot more success with artists than academics, even though artist have way more to lose. I think that academics are strangely politically inactive as a group. (Academic publishing, how could that happen?)
(DIR) Post #ARZe0aMJl9vRFQTzay by mike@sauropods.win
2023-01-12T17:32:29Z
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@john I think there is something in what you say. Artists by nature tend to be looking for the next new thing. Academics by nature tend to consolidate what they have, and are reluctant to bite the system that got them where they are.
(DIR) Post #ARZetT4EZUSmYnC6Ma by llewelly@sauropods.win
2023-01-12T17:42:26Z
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@john has anyone tried to research the question of how many cases of obvious sexual dimorphism we would find in modern birds if pared down only to the sample sizes and remains found in Mesozoic fossils?That being said, I thought there was a case of a Jehol bird in which two individuals were found together with eggs, and the only difference was one had very long tail feathers, and this was hypothesized to be sexual dimorphism.But now I'm having trouble turning up a reference to it.
(DIR) Post #ARZfKoK7eJJOIufDxA by john@sauropods.win
2023-01-12T17:47:24Z
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@mike Like shark, we only move forward.
(DIR) Post #ARZh07rvz764kYkAOO by john@sauropods.win
2023-01-12T18:06:04Z
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@llewelly I think that was Confuciusornis? I bet no one has done such a thing. Because not a lot of ground-truthing research is done.
(DIR) Post #ARZhL7lZYrdMVrmTEu by llewelly@sauropods.win
2023-01-12T18:09:53Z
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@john yeah, I'm sure that kind of ground-truthing is really hard, time consuming, and expensive. But without it, how do you know if the paucity of Mesozoic sexual dimorphism examples is strange?
(DIR) Post #ARZhe4DUyzXh0RsLlA by john@sauropods.win
2023-01-12T18:13:19Z
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@llewelly I think what makes it particularly odd is that we have some many dinosaurs with what look like sexual display structures, with no dimorphism.
(DIR) Post #ARZhi8fuLi07zX6b1k by palaeo3d@troet.cafe
2023-01-12T18:13:59Z
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@john nope, it is to be expected. Given the paucity of fossils, the reduction in almost all cases the bones, the incompleteness of specimens, the unknown time within a fossil population.......no, I don't think we should expect to see many clear examples! After all, true bony dimorphism that is easy to show is so often size-related, and size is out the window if you have much time in your equation.
(DIR) Post #ARZmruNIs3NiJ6sgZE by llewelly@sauropods.win
2023-01-12T19:11:50Z
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@john by the way, thank you, it was Confusciornis.
(DIR) Post #ARa5ENIZoOyLYgX5M0 by DinoDadReviews@sauropods.win
2023-01-12T22:37:07Z
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@john SO weird… how the hell are hadrosaurs and ceratopsians NOT sexually dimorphic?!?
(DIR) Post #ARa7ScOyefpYMYRime by keesey@sauropods.win
2023-01-12T23:02:29Z
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@john Given that a lot of sexual dimorphism is not skeletal, and that it's hard to distinguish subadult and adult dinos (blurring the lines between dimorphism in adults), maybe not?
(DIR) Post #ARjFdsdNBzKRwnhSYS by robknell@ecoevo.social
2023-01-17T08:46:36Z
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@john @DreadShips To get an idea of how badly wrong we can get it for a recent and richly preserved extinct species see the moa paper Bunce, M., Worthy, T.H., Ford, T., Hoppitt, W., Willerslev, E., Drummond, A. & Cooper, A. (2003) Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis. Nature, 425, 172–175.
(DIR) Post #ARjK675tQK6yiel3h2 by dave_hone@sauropods.win
2023-01-17T09:36:32Z
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@john Yes and no. I think it was out there a lot and so we will turn some up sooner rather than later, but it's also not *that* common and given how many dinosaurs are known from a couple of specimens, I can easily buy that we've not found them, or the dimoprhism was primarily size and colour and so very hard to iD.
(DIR) Post #ARjfDu0O4MUBTljoy8 by john@sauropods.win
2023-01-17T13:33:18Z
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@dave_hone I guess it feels odd because we do know of a lot of display structures, but none are obviously dimorphic.
(DIR) Post #ARjg3UV88dGzRCiWsi by dave_hone@sauropods.win
2023-01-17T13:42:21Z
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@john true-ish. I mean we don't have dozens of good skulls of most apart from the ceratopsians but then there are loads of bovids where both sexes have horns so that might track. And the long growth of dinosaurs cf mammals and birds would likely make it cryptic to us but clear in living animals.
(DIR) Post #ARjnKGb9mUJ2vATyQi by john@sauropods.win
2023-01-17T15:04:02Z
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@dave_hone I thought there were quite a few hadrosaurs as well? (The other obvious contenders.)
(DIR) Post #ARkKNPCTYKfSxJ2h0K by dave_hone@sauropods.win
2023-01-17T21:14:23Z
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@john Again, sort of. I really don't think we actually have that many good skulls (like a dozen plus) of adults at one time and place for any taxon.
(DIR) Post #AV6E8sASUroPTenbea by kirt@mastodon.social
2023-04-28T04:24:25Z
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@john @kirt@ecoevo.social how would you know they're the same species? or is that your point?if we found male and female gorillas (without finding them in a big group) we'd mainframe think they were separate?