Two groups of dinosaurs moved to cooler climes during a period of climate change.
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When warm-blooded dinosaurs first roamed the Earth
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https://birdfact.com/articles/are-birds-warm-blooded-or-cold-blooded
Sinxe nowadays we know dinosaurs became birds or are birds, it makes sense.
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I can’t imagine basking having been important to most sauropods. Wouldn’t the square-cube relationship of body volume to surface area have made basking a waste of time? Plus, it seems like at some size being able to reject metabolic heat becomes an issue, more so than how to acquire more heat.
That’s not to say I’m claiming that means sauropods were warm-blooded. Only that on first blush (to a layman) there seems to be an issue with the idea of the sauropods needing to bask. At the very least, for instance, they still might have needed relatively warm temps, even if basking, per se, wasn’t an important factor.
That’s not to say I’m claiming that means sauropods were warm-blooded. Only that on first blush (to a layman) there seems to be an issue with the idea of the sauropods needing to bask. At the very least, for instance, they still might have needed relatively warm temps, even if basking, per se, wasn’t an important factor.
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So the pigeon who sun bathes in my bird bath most days is channeling their ancestral sauropod.
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The way the author refers to the Early Jurassic Jenkyns Event, it makes it seem like there were only two choices: too hot and too cold. Wouldn't there have been a mild climate dinosaurs could have migrated to between the two extremes?
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"... Known as the Early Jurassic Jenkyns Event, the researchers now think that these disruptions pushed theropod and ornithischian dinosaurs to cooler climates because temperatures in warmer zones went above the optimal temperatures for their survival."
Overall the article is interesting and informative. This particular line of thought seems bogus to me. Some event causes part of the planet to now be uncomfortably hot for some species. So they migrate to someplace cooler. But that cooler doesn't need to be cold, it just needs to be cooler than the new hot, like maybe the temperature that the regions that are now too hot were like before. If there was not enough pressure to make them migrate to the poles before, why would there be one now?
We're seeing some of this in the current global warming, with some bird and fish species' territories gradually shifting pole-wards. But gradually, essentially just maintaining those species' territorial temperatures.
[edit: Ninja'd by a couple of minutes.]
Overall the article is interesting and informative. This particular line of thought seems bogus to me. Some event causes part of the planet to now be uncomfortably hot for some species. So they migrate to someplace cooler. But that cooler doesn't need to be cold, it just needs to be cooler than the new hot, like maybe the temperature that the regions that are now too hot were like before. If there was not enough pressure to make them migrate to the poles before, why would there be one now?
We're seeing some of this in the current global warming, with some bird and fish species' territories gradually shifting pole-wards. But gradually, essentially just maintaining those species' territorial temperatures.
[edit: Ninja'd by a couple of minutes.]
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What about fungi? I thought they also brought an evolutionary benefit to warmblooded creatures, especially during these troubled times with average temperatures falling.
I can see them putting evolutionary pressure to keep coldblooded dinosaurs out of more temperate regions.
I can see them putting evolutionary pressure to keep coldblooded dinosaurs out of more temperate regions.
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I would also point out that as egg layers, dinosaurs would have also needed to deal with how to incubate eggs at appropriate temps. Perhaps sauropods couldn’t keep eggs warm by sitting on them (being huge and featherless), so were limited to climates where eggs would be warm enough by themselves in nests. They may have even tended/protected such nests, but maybe couldn’t control temp outside of certain ranges, while lighter, feathered theropods could sit on eggs like modern birds do.
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Not even an African sparrow could carry a one-pound coconut. It would have to be a swallow.
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If the colder regions were full of lush plants that had nothing much eating them, could be a strong inducement for hungry critters to push their cold tolerance limits to take advantage.
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I don't think that a sparrow could swallow a one-pound coconut.
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In those new cold climates, the theropods needed to ingest Theraflu.
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Yep It's Me
Ars Centurion
From the article ...
In a nice bit of timing, PBS Eons just posted a video on the formation of the Mid Atlantic Rift that split apart Pangea through the effects of volcanism. It also belched massive amounts of gases into the atmosphere, creating a cooling effect that these dinosaurs would have experienced.
View: https://www.youtube.com/watch?v=NzOPAoRWOLg
In a nice bit of timing, PBS Eons just posted a video on the formation of the Mid Atlantic Rift that split apart Pangea through the effects of volcanism. It also belched massive amounts of gases into the atmosphere, creating a cooling effect that these dinosaurs would have experienced.
View: https://www.youtube.com/watch?v=NzOPAoRWOLg
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This smacks of the authors being stuck viewing everything through the slit of their study area. Sauropods were large surface grazers (except for brachiosaurids, that tended to eat up), and everything about their in body plan and even defense was predicated on "big" . The most parsimonious explanation for them staying in warmer latitudes is that is where you'd have sufficient food for that lifestyle.
The corollary is that you'd expect brachiosaurids to be the least impacted by this limitation, but single animals were the size of mammoth herds, the fact that mammoths could pull it off doesn't mean anything for sauropods.
We know that sauropods had avian style lungs, and that is inconsistent with low metabolic temperatures.
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One thing that gets lost in the mix is this simplified high school idea of cold blooded vs warm blooded.
Its a continuum. There are a huge variety of heat strategies for species that partially regulate their body temp and are not simply at the mercy of the weather.
Heck by this simpified reasoning taught in high school, a hummingbird is not warm blooded, because every night they let their body temp decrease to the ambient air temperature.
Its a continuum. There are a huge variety of heat strategies for species that partially regulate their body temp and are not simply at the mercy of the weather.
Heck by this simpified reasoning taught in high school, a hummingbird is not warm blooded, because every night they let their body temp decrease to the ambient air temperature.
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What I would expect but wasn't actually written in the article is that it's about seasons.
Higher latitudes would have been comfy in spring and fall, warm but survivable in summer, and cold in winter.
And once you can survive winter sometimes, maybe now it's less adaptation to move further and further polewards to where summer is nice, fall and spring are cold, and winter is fucking cold.
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If global warming creates an advantage for cold-blooded species, does that mean the lawyers win?
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Birds (class Aves) are dinosaurs but dinosaurs (clade Dinosauria) are not birds: Dinosauria is a large clade that includes several levels of smaller clades til the class Aves, and birds lived along other dinosaurs for millions of years.
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If they moved toward the poles to escape the equatorial heat, they would have had to contend with cold winters, even if they still had temperate summers. And there were arctic dinosaurs, so they did survive cold (and dark) winters.
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Per the study, it's not primary productivity that kept sauropods in hot places because they stayed in those environments despite higher productivity in mid latitudes (where it was cooler, but also wetter).
Instead, it must have been their inability to tolerate the colder weather.
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Elephants have the largest mass to surface area of any extant animal. And have mammalian hot bloodedness to keep them going. Yet their range is limited to hot countries. Why?
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Carrying a coconut does indeed sound impractical, but swallowing it sounds like a really big ask even so...!
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Because the cold-weather evolved elephantidae died out at the end of the last ice age.
But maybe your point is that the cold-weather evolved ones had thick fur.
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No fur. Mammoths had plenty of fur to stay warm in the arctic.
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They'll have to balance the cost of migration (including all its risks) against the cost of trying to stay put and survive harsh winters (again including the risks of freezing or starving); In our ecosystems today we've got both strategies, but the costs of either one are not trivial.
And of course the mirrored effect with harsh droughts and heatwaves.
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It's not easy to get a passport when you're too big to get into the photo booth.
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Elephantidae were limited to Africa because they didn't have boats. When Africa and Asia connected via a land bridge, they spread across it and pretty quickly mastodons and mammoths evolved.
For a clade more on par with therapods, you'd be looking at a group of mammals that includes, beyond the elephants, a whole bunch of animals that went over the land bridge to North America via the Arctic, along with a bunch of aquatic mammals. Clearly, they didn't have much trouble adapting to various climates.
The aquatic mammals did have boats, so we have had manatees in the Americas since before Africa got connected to Asia.
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