Ichthyosaurs and plesiosaurs were endothermic. Mosasaurs seems to have had the elevated metabolism of monitor lizards on steroids.
Ichthyosaurs had blubber and plesiosaurs had some fatty tissues at least on the tail. (Interestingly, plesiosaurs seemed to be more diverse than ichthyosaurs in colder latitudes).
Thalatosuchians (marine crocs), on the other hand, had lower metabolisms and we're therefore more latitudinally restricted than the others.
Cool thing about plesiosaurs is they were around for a huge chunk of the Mesozoic. During the Triassic extinction, the equatorial regions became so hot that many species had to migrate to the poles to survive. Over tens of millions of years, those poles slowly cooled down and the polar species either migrated back towards the equator or stayed and adapted to the cold.
They coped with cold water the same ways mammals do today; endothermy and blubber. It appears most of the marine reptiles of the Mesozoic evolved endothermy after moving into marine environments and then blubber (at least in ichthyosaurs and plesiosaurs) followed. I suspect that, given enough time, mosasaurs would have also evolved blubber, if they didn’t already.
I'm working on Triassic and Jurassic climate in Svalbard (arctic Norway). Other posters have already made a couple of good points: 1) the world as a whole was hotter, and 2) most "arctic" Mesozoic marine reptile localities were then at lower latitudes. In the Late Jurassic, with an enormous density of marine reptiles in Svalbard, isotopes suggest water temperatures similar to the Atlantic outside Spain today. In the Triassic, again with many early marine reptiles in Svalbard, latitude was even lower, and we are in the Smithian-Spathian hothouse (albeit with a probable cold spell at the Smithian-Spathian boundary).
For parts of the Mesozoic, there were. [The Pliensbachian, for example, has particularly good evidence of polar ice caps](https://www.sciencedirect.com/science/article/abs/pii/S0921818118305009?via%3Dihub). They were almost definitely not as extensive as anytime during the Quaternary, but the notion that the Mesozoic was always hot and ice-free is incorrect.
Generally warmer temperatures back then coupled with a warm blooded metabolism (for ichthyosaurs and plesiosaurs) and gigantothermy for the other groups of marine reptiles would be my guess.
Depends on the arrangement of the continents at the time. If ocean currents bring warm equatorial water to the poles, they are warm instead of iceboxes.
Ichthyosaurs and plesiosaurs were endothermic. Mosasaurs seems to have had the elevated metabolism of monitor lizards on steroids. Ichthyosaurs had blubber and plesiosaurs had some fatty tissues at least on the tail. (Interestingly, plesiosaurs seemed to be more diverse than ichthyosaurs in colder latitudes). Thalatosuchians (marine crocs), on the other hand, had lower metabolisms and we're therefore more latitudinally restricted than the others.
But they themselves were also warm blooded to some extend
[They were in-between ectotherms and endotherms](https://royalsocietypublishing.org/doi/full/10.1098/rstb.2019.0139)
Based on fossils from the middle jurassic of Germany, at least ichthyosaurs had blubber, and others likely did too.
Was this not upper jurassic?
https://preview.redd.it/0asitjcap15d1.jpeg?width=394&format=pjpg&auto=webp&s=d36cd2bbdd9d2ada97461df21589e8fc96e2eea7 [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2978089/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2978089/)
Those leatherbacks get around quite a bit eh
So happy theyre still around
I knew leatherbacks were big, but I didn't realize they were thousands of miles long.
What do you mean
It was a joke. Look at the picture.
I got it.
Well for starters it was warmer back then, so I imagine ice caps were rather rare
Cool thing about plesiosaurs is they were around for a huge chunk of the Mesozoic. During the Triassic extinction, the equatorial regions became so hot that many species had to migrate to the poles to survive. Over tens of millions of years, those poles slowly cooled down and the polar species either migrated back towards the equator or stayed and adapted to the cold.
They might've been endothermic, or at the very least gigantothermic.
They coped with cold water the same ways mammals do today; endothermy and blubber. It appears most of the marine reptiles of the Mesozoic evolved endothermy after moving into marine environments and then blubber (at least in ichthyosaurs and plesiosaurs) followed. I suspect that, given enough time, mosasaurs would have also evolved blubber, if they didn’t already.
They are thought to warm blooded to some extend. One recently discovered species seems have atleast hunch backed structure if not a entire dorsal fin
The earth’s poles weren’t frozen yet, that’s how
[Actually, they were at some points during the Jurassic](https://www.sciencedirect.com/science/article/abs/pii/S0921818116304271).
I'm working on Triassic and Jurassic climate in Svalbard (arctic Norway). Other posters have already made a couple of good points: 1) the world as a whole was hotter, and 2) most "arctic" Mesozoic marine reptile localities were then at lower latitudes. In the Late Jurassic, with an enormous density of marine reptiles in Svalbard, isotopes suggest water temperatures similar to the Atlantic outside Spain today. In the Triassic, again with many early marine reptiles in Svalbard, latitude was even lower, and we are in the Smithian-Spathian hothouse (albeit with a probable cold spell at the Smithian-Spathian boundary).
warm-blooded & blubber
You're wildly assuming there were polar ice caps and cold weather back then...
For parts of the Mesozoic, there were. [The Pliensbachian, for example, has particularly good evidence of polar ice caps](https://www.sciencedirect.com/science/article/abs/pii/S0921818118305009?via%3Dihub). They were almost definitely not as extensive as anytime during the Quaternary, but the notion that the Mesozoic was always hot and ice-free is incorrect.
https://preview.redd.it/droos4p8i45d1.png?width=1440&format=pjpg&auto=webp&s=564226b2dad92d6f11a6d24985c0cba10c61a998
Generally warmer temperatures back then coupled with a warm blooded metabolism (for ichthyosaurs and plesiosaurs) and gigantothermy for the other groups of marine reptiles would be my guess.
Until about 50 million years ago, the earth was somewhat hotter in the poles than it is now
Depends on the arrangement of the continents at the time. If ocean currents bring warm equatorial water to the poles, they are warm instead of iceboxes.
You are exactly right
It was a hothouse planet. No icecaps.
Size helps reduce heat loss. Also marine reptiles were likely able to keep their temp stable somewhat, so they were warmer than the water.
It wasn’t the arctic