Mesozoic Marine Reptiles: Dolphins🐬 or Sea Monsters🦈? GEO GIRL

[@NaturesCompendium]

In addition to the oxygen isotope studies, the discovery of a well preserved species Stenopterygius with soft tissue preservation showed that they had blubber as well, further supporting them being warm-blooded! Ichthyosaurs turned out to be a lot more with dolphin-like than we previously thought 💙🐬

[@GEOGIRL]

So cool! Thanks for sharing :D

[@donaldbrizzolara7720]

Rachel: I find it interesting that the ichthyosaurs didn’t appear to check out at the K/P boundary, but earlier. The end of the ichthyosaurs may have occurred in a two stage process. An initial event at the beginning of the Cenomanian removed two of the three ichthyosaur feeding types or guilds still present. A second extinction event probably occurred at the Cenomanian-Turonian boundary event, a proposed marine 'anoxic event', after which a single ichthyosaur lineage survived, Platypterygius hercynicus, which then disappeared about 93 million years ago. Ichthyosaur extinction would then appear to result from a pair of relatively rapid events rather than a long, draw out one and was more than likely related to environmental and climatic changes in the Cenomanian and Turonian.

[@robinleow185]

I am comfortable with this topic on marine reptiles (monsters) of the Mesozoic Sea because I’ve written short articles on the geology of Australia (where I come from) in facebook. These articles were written (based on actual evidence found in the fields) right from the beginning of time ~4.4 Ga ago with the discovery of Hadean zircons at Jack Hills to Anthropocene. The article on Cretaceous Period (145 to 66 Ma ago) - Coober Pedy, SA, mentioned were made on the Ichthyosaurs and Plesiosaurs found in the then Eromanga Sea (Cretaceous) that spread out over a quarter of Australia. Opalized plesiosaurs were also discovered at Coober Pedy, SA. Kronosaurus queenslandicus (the name queenslandicus from Queensland, a state in Australia) were also discovered in the Eromanga Sea.

[@GEOGIRL]

Opalized plesiosaurs, wow! That'd be so cool to see! :D

[@SydWalker3k]

Apparently his name is Eric. He has very colourful vertebrae. Incidentally, I think your channel is awesome. Discovered it a week or so ago and I'm spending way too much time here already :-) @@GEOGIRL

[@GEOGIRL]

@@SydWalker3k Oh that is so cool! And thank you so much! So glad you have been enjoying my videos! :D

[@brucewilliams4152]

I had a wonderful conversation with a paleontologist at the Oxford natural history museum. She recently was one of the team that dug up the ichythiosaur found in Rutland water

[@GEOGIRL]

Wow that is so cool! :D

[@billkallas1762]

Meters to feet is easy. Just multiply by 3 (very roughly) or 3.3 (less roughly). Convergent evolution is very interesting.

[@fabiana.4640]

Another excellent vid! You forgot the marine iguana among the sea reptiles. I would love a video comparing many of these marine reptiles of the Mezozoic with those gigantic predatory marine mammals from the Eocene such as Basilosaurus that looked like the sea monsters of the Mezozoic.

[@GEOGIRL]

Oh yea, great point! ;)

[@mikesnyder1788]

English Literature major here reporting in... And I love the content in this video! Thank you for presenting the information in a clear and concise manner.

[@andrewschaeffer8147]

A meter is 40 inches. 3 feet is 36. The safe conversion is just to triple the meters to get the feet

[@forestknowledge]

Definitely over 65 ft

[@stevenkobb156]

When most of the non-avian dinosaurs became extinct, before mammals became so dominant, we also had a long period of birds evolving to fill many ecological niches. I imagine many of these birds preyed on reptiles.

[@robinleow185]

A totally remarkable educational video on the reptiles of the Mesozoic Sea and they were actually monsters just like the dinosaurs counterpart on land! That is good to be reminded!

[@GEOGIRL]

Thank you! So glad you enjoyed the video :D

[@forestknowledge]

GEO Girl is the coolest! Another great video! :)

[@pumaconcolor2855]

To be honest I wouldn't be surprised if we find out it existed a fully aquatic lineage of mesozoic (stem)mammals. Castorocauda was already semiaquatic and there are plenty of examples of marine amniote lineages arising while more dominant and specialized lineages exist (Mosasaurs, Pinnipeds, Hesperornithes to name a few).

[@madhealerofwindurst807]

Thank you for a great documentary on marine reptiles!

[@wolfpackastrobiology3690]

What's really interesting is that we recently found out that there were some very large raptorial ichthyosaurs. Although we knew that some ichthyosaurs grew to the size of whales in the late Triassic for some time, it was thought that the larger ones lived like modern sperm whales. But just last year we identified a 40-60 tonne ichthyosaur from the late Triassic of Switzerland that had clear adaptations for hunting large prey and it was likely more powerful than Pliosaurus funkei and comparable to Megalodon and Livyatan.

[@madsgrams2069]

Yes and Himalayasaurus is now being reexamined as well, as it too seemed have had similar teeth, but was labelled by some researchers to be a domen dubium. In fact, all of the Shastasauridae family of ichtyosaurs might have been erroneously branded as toothless suction feeders that hunted almost exclusively cephalopods, so now even the more famous members of the group, like Shonisaurus sikkaniensis, are being reeexamenined as well. It's possible they were more similar to Thalattoarchon than to the genus that gave the name of the family, Shastasaurus.

[@Ornitholestes1]

~2:30 placodonts actually did have shells, at least many of them (see _Henodus_ ). Possible convergence between basal Sauropterygians and stem-turtles is actually a really major issue in figuring out the latter’s relationships. Turtles might or might not turn out to be close relatives of Sauropterygians, or even surviving members of sauropterygia. 3:11 Actually, the oldest Plesiosaurs are from the uppermost Triassic (see Wintrich et al. 2017). There is one complete skeleton of a definite Triassic plesiosaur, and also various isolated bones from Rhaetian bone beds in the UK, Germany, and I think France if memory serves me right. 8:40 Some ichthyosaurs laid eggs? Not so sure about that. We know very little about ichthyosaur(omorph) origins, but by the time they turn up in the fossil record, they are already fully aquatic. There is no fossil evidence of any ichthyosaur laying eggs, in fact even very early members back in the Middle Triassic were already viviparous (there definitely is a known pregnant female specimen of _Omphalosaurus_ , which is fairly basal, although I think it’s unpublished). Maybe even more basal ichthyosaurs did lay eggs at some point, or maybe viviparity evolved earlier in Ichthyosauromorph evolution. We don’t have definite proof of how the closest relatives of ichthyosaurs, Hupehsuchians, reproduced, but they have been suggested to have been viviparous as well due to their extensive aquatic adaptations (see Carroll and Dong 1997). 12:53 The image you show here (the skeletal reconstructions) look like they come from one of David Peters’ websites, likely reptileevolution.com (or, less likely, pterosaurheresies). Be very careful about that source, David Peters is a very talented artist, and easily capable of fooling many people into believing his science is legit, but he is a proponent of total crackpot ideas (such as Pterosaurs being lizards rather than archosaurs) that are based on completely flawed methods. These include subjecting published images of specimens to "image analysis" in photoshop and thus somehow being able to discern not just anatomical details, but weird and outlandish structures that for some inexplicable reason nobody who looked at the actual specimen has been able to see, such as ridiculous soft-tissue flaps, and even unossified embryonic pterosaurs, that are apparently supposed to be hiding on well-known slabs in plain sight. His phylogenetic methods are also very bad, based on far too few characters to be of any worth. That’s why I would recommend not to trust any phylogenetic analysis he proposes, unless it has been verified in a published work, based on sound methods. A good summary of the issues with that site is given here: tetzoo.com/blog/2020/7/23/the-david-peters-problem As for the ichthyosaur-mesosaur relationship is looks like he might be proposing, that is utter BS, I have literally never seen this suggested by a peer-reviewed phylogenetic analysis, which always place Mesosaurs as very basal Sauropsids while Ichthyosaurs are recovered as saurians, or at least close relatives of Sauria. Never say never, esp. with the remaining uncertainties about where ichthyosaurs came from, but I wouldn’t take Peters’ word for it. --- Wintrich, T., Hayashi, S., Houssaye, A., Nakajima, Y. and Sander, P.M. 2017. A Triassic plesiosaurian skeleton and bone histology inform on evolution of a unique body plan. Science Advances 3 (12): e1701144. Carroll, R.L. and Dong, Z.-M. 1997. Hupehsuchus, an enigmatic aquatic reptile from the Triassic of China, and the problem of establishing relationships. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 331 (1260): 131-153.

[@neptunethemystic]

I could listen to you for hours! Thank you

[@GEOGIRL]

Thank you so much! So glad you enjoyed the video :)

[@curtisblake261]

It continues to fascinate me the points during your presentation at which you chuckle or laugh. I'm sure those moments say something but I'm not sure what they say. To be continued...

[@nieselregen420]

Hey there, I recently stumbled upon your channel and I'm surprised that every video sparks my interest. You chose great topics, present them really well and I can see your passion in these things! Could talk about these kind of things all day. Also love your rock collection from the mineral videos. Hope your channel blows up, you deserve it. Thank you!

[@ptredhead]

Great video! I think convergent evolution is so fascinating. Maybe you could do a video about all the times things evolved to look exactly like other things.

[@GEOGIRL]

That’s a great idea thanks!

[@br7693t]

Thank you for what you do. I've made dozens of links to your videos for my intro paleontology students.

[@GEOGIRL]

Oh my gosh, thank you so much! I am so glad you find the videos helpful enough to share with your students ;D

[@joecanales9631]

Hi, thanks for your video. I liked your comparisons with modern analogs for the Plesiosaur, or lack of one except for mythical. The Nothosaur did remind me of the iguanas of the Galapagos. BTW, did you catch my note about the EGU article on the Volyn Biota? Actually I originally saw it presented by Anton Petrov’s video. Very cool fossils from the ‘Boring Billion’. It covered some geochemistry.

[@asthemoonturns]

Another channel just uploaded a video about Hupehsuchus (close family of the Ichthyosaurs). Research indicates that it was a filter feeder. So they were even more whale-like than we thought.

[@artificercreator]

Oh, that is a nice point! Thanks for the video

[@robbabcock_]

Truly fascinating stuff, GG!

[@Alberad08]

Thank you for this video! I like that topic very much.

[@shadeen3604]

Amazing information about Marin lives easy to understand thank you geo girl excellent

[@GEOGIRL]

Thank you! So glad you enjoyed it ;D

[@leechild4655]

I could be wrong but it seems the size of eye balls in many ancient creatures has gone mostly misrepresented. Maybe to do so would `look wrong` to us? idk but look at the orbital structures of some of these things. It makes no sense to believe a small eyeball resided in these large orbits. Maybe I`m just way off base but, I just have to go with what seems obvious from observations.

[@davidrogers8030]

A fascinating variety of animals long gone to sea in this vid.

[@GEOGIRL]

Agreed, so facinating! I wish we could go back and visit them :D (but not too close up lol)

[@footfault1941]

Thank you for a nice selection of topic. During a so-called age of dinosaur, those Reptiles enjoyed an immense space for life. That's a kind of conundrum why not dinos tried to extend further their home territory! Back to the main subject, those marine reptiles' apparent success is just stunning. Divergence in shape & size, the latter in particular, is simply unmatched in nature anywhere else. Large-sized ichthyosaurs would be equivalent to enlarged orcas or great white in modern time. Mostly their pelagic lifestyle is another feature, sign of exquisite adaptation. The footage presented well those points. Elaborated as usual. That's said, personally the efficiency under water of ichthyosaurs provokes bits of skepticism. As clear in fossils, they had elongated ribs, which is construed as a plumpy body contour in reconstruction. Hydrodynamically it looks less sophisticated than cetaceans. Agility like that of dolphins ..? Anyway, unlike sea turtle or marine snake, the reproductive strategy of ichthyosaur is a hallmark of fully adapted to marine life. Amazing, isn't it? An important, intriguing & controversial subject of being warm-blooded may find a reference - tuna. They can raise body temperature 10°C higher than that of surrounding water. It's (I suspect) the work of their muscular body (sorry, but unknown about its physiological mechanism). Unlike mammals, they might not be homeothermic, but might have a similar physiology or faculty. Curiosity is inevitably directed to their ancestral forms on land, which is covered, or well-anticipated. Neatly done. For such a morphological diversity, a single stock is hardly suitable for the origin of all. Dinosaurs for some reason discarded a oceanic lifestyle, but much later one of the surviving lineage successfully found ways to explore a vast niche - birds! Note: as you may know, their exploration in the sea was actually already happened in later Cretaceous. Ichthyornis, hesperornis to name a few (although they went extinct).

[@hectorbacchus]

Nice video. I wish you mentioned that it’s unknown how exactly ichthyosaurs breathed. The nostrils are sometimes is weird places. So maybe they breathed in and out from the tip of their mouths?

[@GEOGIRL]

Oh interesting I didn't know that! Thanks for sharing :D

[@fernbedek6302]

I think I’ve heard Plesiosaurs be compared to penguins (and other diving fish)? Much bigger, of course. But very ‘lead with the neck’.

[@wagon9082]

Good video

[@takingbacktheplanet]

😱... oh man, monitor lizards adapting to aquatic life sounds scary. 😅

[@billyr2904]

Mosasaurs were the biggest lizards to ever live. Recent evidence suggests that the closest relatives of mosasaurs are snakes, but there is some debate whether snakes or monitor lizards are there closest relatives.

[@sydhenderson6753]

There's evidence now that the largest Triassic ichthyosaurs rivaled the blue whale in length (judging from jaw size) but probably not in weight. They were also toothed rather than having baleen. I don't know of any analogues to the baleen whales.

[@GEOGIRL]

Wow that is so cool!! Thanks for sharing that ;D

[@oqsy]

With the internet being how it is, I want to preface this by saying it’s an honest question, not at all meant to be rude. Where did you get your pronunciation of “Cretaceous”? I have never heard anyone else say “Cray-“, but you clearly know your stuff, so I’m honestly curious if someone stressed to you at some point to say “cray-taceous”, and if we are all saying it wrong or at least the colloquial pronunciation isn’t preferred for some reason. Great vid as always and I appreciate your time and effort!

[@GEOGIRL]

Oh, I never thought about it this is just how I always heard it haha, what other way is there to say it? Now I am curious haha ;)

[@oqsy]

@@GEOGIRL Other than regional accents, I usually hear “cruh-taceous” or “cree-tacious”. Language is funny 😂 English was my major until I decided I’d like to make money after college. 😂

[@GEOGIRL]

@@oqsy Oh I see haha yea, I think it should be more of an 'uh' sound than what I say, but I think when I say it quick I just tend to give it more of a 'ay' sound so I would say that is more of my accent than a purposeful pronouciation haha. But I haven't heard anyone say it with an 'ee' sound, that is new to me. I agree, I think it is largely influenced by regional accents ;)

[@oqsy]

@@GEOGIRL I wonder how much of it is old BBC dinosaur shows I used to watch regarding the “ee” 😂

[@АртурСПб-э6ю]

Спасибо за лекцию!:)

[@GEOGIRL]

Пожалуйста! ;D

[@forestknowledge]

Scientific Proof that the Loch Ness monster is real! 🤯🤯

[@Vadjong]

And long since extinct...

[@davidcora2751]

Very interesting. Thank you.

[@oiocha5706]

I seriously want to know why crocs didn't take over the oceans after the KPg extinction...and what's up with marine iguana's? What's taking them so long to transform into mosasurs!? I WANT MEGAFAUNA!!!

[@youtubejosephwm6699]

Rachel you forgot about Thalattosuchians the Marine crocodiles also all ichthyosaurus plesiosaurs and mosasaurus probably gave birth to live young

[@Paralititan]

Non of the derived marine reptiles laid eggs as their bodyplans prohibited them from beaching themselves. We have direct evidence of live birth for most ichthyosaurs including early forms, one plesiosaur and some more basal eosauropterygians and a basal mosasaur. Live bearing is quite common in reptiles apart from archosauria which exclusively lay shelled eggs. Although we can’t say for sure yet, terrestrial ancestors of these reptiles were likely already livebearing giving their descendants an advantage in aquatic radiation

[@Theorigamian]

I need that table of elements that you have behind you. Where can I find that?

[@mathewritchie]

You have it backwards Dolphins are ichthyosaur mimics.

[@GEOGIRL]

Yep, that's what I said at the beginning, the reptiles set the trend and the mammals copied it in the Cenozoic ;)

[@curtisblake261]

This is not appropriate in this context, but cue the sky high guy from the double rainbow video breaking down over the question "What does it mean"? Full-on double rainbow. What does it mean?

[@jensphiliphohmann1876]

09:00f _We can't say for sure that they didn't jump out of the water._ Like the great white.

[@jimthain8777]

When talking about ancient animals where the evidence points to their having traits similar (a typo of warm blooded system, live birth, were mentioned, are there other things?) to mammals, I wonder if maybe these creatures had evolved to be something that wasn't either a reptile as we would think of today or a mammal either. I have wondered about this since I first heard that some dinosaurs may have been warm blooded too. Could a case be made that these animals actually formed a class of their own different from both reptiles (that they may have evolved from) and the mammals that later succeeded them? We do have at least one long necked mammal (giraffe), that seems to eat similar to long necked dinosaurs, One wonders why there aren't more? Perhaps the reason some body types have been lost is that the type of food they ate no longer exists? Was there plankton, or something like that in ancient seas? It seems reasonable given how important such tiny plants & animals are to our modern seas? If so what would have eaten those things? Huge wales do so in our world but maybe something much smaller would have done so back then. Sorry for the long comment. Your video certainly stimulated my curiosity, that's for sure! Thanks for the video.

[@od1452]

I've seen a number of Ichthyosaur Fossils in Germany and couldn't help thinking of dolphins. Convergent evolution seems to indicate specific niches. Surely someone has tried to quantify and identify them. Do you know of an author? Thanks. Always interesting subjects.

[@colinmetzler]

dang they really filled in every nook and cranny with teeth : D

[@curtisblake261]

Geo Girl is obviously an off the charts scientific genius. Alternatively, she's an historic scientific scam artist. I'm going with the former

[@GEOGIRL]

Hahaha I am certainly not a genius, but I do my best ;) thank you!

[@madsgrams2069]

You didn't mention the thalattosuchians, the fully-marine crocodiles, which convergently evolved to have a similar body-plan to the mosasaurs that would come much later and filled the niche of medium-sized maarine predators in the middle Jurassic. Also, marine snakes eveolved in the Lower Cretaceous, even earlier than their mosasaur cousins and just continued to exist after the KPg extinction. They're survivors of that age, similar to sea-turtles. The only retiles that evolved a semi-aquatic life-style in the Cenozoic are marine iguanas.

[@billkallas1762]

Do you believe that the K-T extinction was caused 100%, by the 10 to 15 year long "Winter", caused by the Strike Event, or are there other theories about secondary causes?

[@GEOGIRL]

Oh no, there are so many other causes besides the impact winter! I don't think any extinction events are caused by such a singular event or factor. I actually have a video discussing the KT event and all the causes that you can check out if you want:https: //kzbin.info/www/bejne/q2OahJSErN2XZtk I think in the end, I listed like 7 causes :)

[@billkallas1762]

@@GEOGIRL Thanks.

[@nicholasmaude6906]

We've heard of Mammal-like Reptiles, Rachel, would it be fair to describe Ichthyosaurs as Dolphin-like Reptiles?

[@JasonKale]

Someone some day can now say Im so old I remember when dolphins were reptiles..hahaha lol

[@GEOGIRL]

Lol I am going to use that someday ;D haha

[@JasonKale]

@@GEOGIRL After you said proto turtle I got to thinking about snapping turtles as they are prevalent in my part of PA.. I knew they have been around for some time but just learned they have been around for nearly 90 million years and survived the mass extinction that killed the dinosaurs. Maybe there is grounds for a future video...Proto turtles to snapping turtles...They must be tuff little buggers Surviving even PA winters...lol. They are sort of an anomaly on the north american continent would you not say?

[@mapache-ehcapam]

All of this makes me wonder, if there were any ''primate'' like animals in the Mesozoic, or alternatively what Mesozoic animals occupied a niche similar to our recent primate ancestors. Because sadly, I doubt there were any animals occupying the niche of modern humans... right? do we even have a niche?

[@GEOGIRL]

Those are great questions! First, yes, we absolutely have a niche :) We have of course, expanded to live in basically all ecosystems and make food in many different ways now, but in general, we do have an ecological role or niche, that is we are terrestrial, bipedal, non-climbing tetrapods that hunt and farm, eat both meat and veggies and we are basically the apex predators of whatever environment we end up in (except for marine ones, as of now at least haha). So there could be another primate (or other animal) species to eventually fill this same role on either future earth once we have gone extinct or another earth-like planet. But no, there were no primates yet in the Mesozoic, only very small rodent-like mammals until the dinos disappeared :) I would say that given the incredible diversity of dinosaurs throughout the mesozoic, there were potentially ones that filled similar roles to modern day primates, but I can't say for sure nor can I name species, I will have to look more into it. What an interesting thought though, thank you for sparking this conversation! ;D

[@DominikJaniec]

learning about examples of convergent evolution, I've convinced myself that alien creatures will not look that different from what we know here, and in the end everyone will become a crab via Carcinisation ;)

[@GEOGIRL]

Oh really? I guess if their planet was similar to earth I could see that potentially happening, but what if it was really different? Ya never know ;)

[@DominikJaniec]

@@GEOGIRL right, fully agree - environment is the key

[@SSNewberry]

"Reptiles" as you use it means 0. It is non-cladistic. It has no defining feature. It is "the wastebin for all non-mammal, non-avian amniotes" which is not match by the current examples. Razie award.

[@reidflemingworldstoughestm1394]

Hey wait a minute. Didn't this used to be a geology channel?

[@GEOGIRL]

This is geology (this is actually taken from part of a lecture I give my real life historical geology students 😉)

[@reidflemingworldstoughestm1394]

@@GEOGIRL That is a relief. You gave me quite a scare there.

[@aaronmeehan8161]

Do we think large icthyosaurs and small icthyosaurs are more closely related than dolphins and sperm whales?

[@curtisblake261]

With most people, I own their brain as soon as I meet them. Or at least that's my narcissistic take on it. But Geo Girl is more elusive than I've met before as a purely platonic matter. Seems like she should be in the government lab somewhere with electrodes in her brain. Or maybe she is and that's how Earth 2.0 started. Forget that last comment. Earth 3.0 is just around the corner and you could be part of the vanguard GeoGirl. Do I sound crazy? Yes, I probably am but Earth 2.0 made me this way.

[@paleontologico]

1 meter is more or less 3 feet

[@jensphiliphohmann1876]

14:25f There is an ocean but it's kind of empty. Why should land animals return there just to starve?

[@OzGeologyOfficial]

👋👋

[@johnvl6358]

😎😎

[@the_eternal_student]

It would be nice to turn into a dolphin when you needed to swim in deep enough water and then turn back into a human when you needed to build a machine. What I got out of this video is that evolution is trying to create a single species that can transform into what ever form is necessary in a given environment at a given instant, including being infinitely big and infinitely small.

[@wtywatoad]

Chicken of the Mesozoic Sea

[@terenzo50]

Live births! Good grief! My aquatic heroes (besides dolphins) since childhood have been seahorses.

[@texcatlipocajunior144]

Have no analogs of the modern baleen whales been discovered?

[@AndrewMellor-darkphoton]

hi

[@Moontanman]

You left out the marine crocodiles! Metriorhynchids

[@cavetroll666]

🐟🐠🐡🍥🦎🦎

[@geodkyt]

Ive more commonly heard "suchus" pronounced "Sook-us".

[@GEOGIRL]

Thanks! That is gonna be helpful for future videos :)

[@ashajacob8362]

Are you doing Phd???

[@GEOGIRL]

Yep, I am ;)