BIG THANKS to Dr. Matthew Svensson (recent geoscience doctoral graduate!🎉) for his help researching this topic and putting together this video! I was going to just make this a short (less than a minute) video, but Matt found so much info that I had to make it a full length video and now it is one of my favs! I hope you all enjoy this video and find this topic as interesting as I do! ;D

Whenever Geo Girl talks about exotic prehistoric creatures -- backboned or not -- we know we're in for a good time. 😊 🦖 🦕

Excellent review. I am a Biology prof and had emphasized the deep water habitat as a may reason for nautiloid survival, but I hadn't thought more generally about the other factors you noted. Really appreciate the video.

Would be fascinating to see a video about groups that survived the KPg extinction event only to go extinct shortly after, like you speculated about the ammonites here.

I got a small ammonite fosil from a museum shop after visiting the dinosaur section when I was a kid. I love cephalopods. They're so cute and unpredictable. Pity they lead such short lives. It would be so cool if humans could bond with Octipi and teach them stuff.

Rachel is the best. Very few, if any, can explain science as well as she does.

Rachel: Nice synopsis of the various theories that led to the demise of the Ammonoidea. Worldwide there are scattered examples of ammonite presence extending into the Danian, but no later. Most of my encounters with ammonite fossils has been from largely shallow marine (shelfal to upper slope) sedimentary facies. I think that factor, combined with other theories you mentioned, was very significant. I have always been fascinated by ammonites. When I lived in Eagle River, Alaska I lived quite close to the Talkeetna Mountains which carries a remarkable ammonite fauna extending from the early Jurassic to Late Cretaceous. Many summer days were spent hiking there, studying and collecting ammonites. Boxes in my attic attest to it to this day. Great job on your discussion..I loved it!

Very interesting video! Now I have to wonder if the Nautiloids inhabited the surface ocean niches before the Ammonoids and their higher metabolism outcompeted them when they came on the scene 50 million years later. If Nautiloids were confined to less dominant niches throughout the Mesozoic due to competition, they sound like an aquatic equivalent of the mammals living in the shadow of the dinosaurs!

Historical geology was probably one of the most fun classes I ever took, it was instrumental in my pursuing (and eventually getting!) a geology degree. It has now been a few decades since then, this brings back great memories in a wonderful fashion. 🙂

Geo Girl makes anything from extinction to how do zircons tell us age-related information sound interesting, and I'm here for it!

Subscribed a while back after seeing your channel recommended in a paleontology/earth history-related discussion online. Finally got around to watching and I just have to say that I love how concise you keep your presentation. Thank you!

'Extinction selectivity' is super interesting and relevant. It would be great to know more about impacts on deep sea biomes. Great content. Thank you! 🐸

Highly informative! Nice to see that in an internet landscape that doesn't typically value deep understanding of a topic. Keep up the good work!

As always, thank you for the great explanation :)

I still refer to the end mesozoic extinction event as the KT extinction event, Rachel, now as to the possibility of the Ammonoids surviving into the early Palaeocene I do believe that is what is referred to as a "Dead Clade Walking", well there is some controversial evidence that suggests that there were non-Avian Dinosaurs in the early palaeocene too.

Trilobites and Ammonites really interest me. so cool

In addition to the Ammonoids surviving, Rachel, I'd loved to have seen the giant orthicones survive too.

Glad youtube recommended this! Totally into this stuff. Great video! 😊

Always very good, thank you. Some additional thoughts to chew on for any interested: -It's a truism that drivers of extinction are rarely terminal in groups that aren't already 'stressed'. As noted, Ammonoids were in decline before the KPG. -I'm not sure what this is based on, but it's believed Ammonoids died after spawning. A very risky strategy indeed if your environment is in upheaval. -Nautiloids are detritivores, great when everything is dying. However Ammonoid dependency on the bottom of a collapsing food web was really bad.

Fascinating. . Thank you for your great video 👍👍

Wow lots of good info and clear accessible delivery!

Great topic. I’ve been curious about this for a long time.

Thank you so much for a well presented and informative video.

I recently read Monarchs of the Seas by Danna Staaf, and this video made me geek out over cephalopods! Love your videos!

Thank you geo girl for your explanation so many topics very simple language

Ammonites and trilobites are two lines that I find fascinating, having lived from the the Cambrian for hundreds of millions of years, much of the time being quite successful organisms, but gradually declining over the millennia until the point they disappear from the fossil record by the Cretaceous extinction event at the latest. Particularly interesting considering some ancient lines that manage to plow right on through the great extinctions, such as sponges, jellyfish, corals, and anemones, and horseshoe crabs that started nearly 440 million years ago and continue in the present day. I first wonder how continental movement, resulting in changes to the environment (such as new ocean current flows that develop as continents rift apart and collide, new mountain change develop and begin to erode away dropping great masses of fine-grained sediment, etc. I visualize a sort of web of geophysical and chemical activity that determine if creatures live or die, as well as how well they can evolve to take advantage of and survive in a changing environment.

Thanks for a great video! 🎉

Very interesting! I didn't know we knew about their eggs, nor the fact that ammonoids are younger than nautiloids! What a great first impression your vid has made!

thanks for the video :)

Really really love this video! It's so interesting thank you sm geo girl , and also the rocks/fossils collection behind you looks cool 💓💓

Thank you very much - highly appreciated!

Always had this question, thankyou Rachel you do you❤

Just happened upon this channel and I like it alot. Pleasant to listen to and informative. Subbing, Looking forward to seeing more!

I absolutely love the egg fossils 8:18 ! How did paleontologists determine that those were ammonioid eggs? I always wonder about connecting trace fossils and eggs to the organisms that made them.

Awesome job, Liked the content. Loren

This question has been keeping me up at night! I can finally get some sleep! Thank you!

Peter D Ward covers this exact topic in his book "On Methuselah's Trail: Living Fossils and the Great Extinctions." Great read, I think you'd like it.

Thanks. No idea why this didn't show up until today.

Thank you for the video! ❤ 1:15 - I think there were not only nautiloids as survivors of the extinction event, but many other groups of organisms. We focus on these guys, but should acquire the rest.

Too bad the Ammonoid speciation wasn't diverse enough to include a deepwater version or they might still be around. Reminds me of a line from an old Eagles song: "Now I look at the years gone by and wonder at the powers that be / I don't know why fortune smiles on some and lets the rest go free."

Great video, thanks. Calcium Carbonate polymorphs....? Did ammonoidea have identical shell chemistry to the nautiloids? Or did they make more use of aragonite for their shells, thus depriving them of the deeper water environment due to pressure? Nautilus shell chemistry more calcite? Hence when cataclysmic environmental change happened at the K/Pg they could continue existing in the deep, while ammonoidea were wiped out in the shallows and unable to retreat to a higher pressure niche ? I worked on a foundations drilling rig, as a geologist, and the spoil coming up from the Purbeck/Weald clays in Chichester England contained ammonite fossils, but unaltered! Nacent, pearlescent shells, which is aragonite polymorph of Calcium Carbonate. Beautiful. Not lithified, chemically replaced. It made me wonder about their chemical construction in comparison to the earlier evolved nautiloids.

Great video, I loved it! I really want to wacth a living nautilus and an ammonoid fossil. Amazing creatures

Interesting, thanks!

Lovely talk. Something I’m left wondering is what other creatures took over their niches, as the final stages of decline by residual survivors can be outcompetion by whatever other taxa were in the ascendancy - what other advantages did those others have leading to any takeover (if we accept persistency for some remnants of those ammonoids )

I always thought that nautiloids were just modern ammonoids but I'm glad you explained the difference

I just visited the Paris Natural History Museum and there were a lot of ammonoids fossils.... Quite impressive how big and diverse and weird those things could get in real life .....

In terms of plankton shortage the lack of sunlight was likely a bigger role as acidification was a problem for all of the major mass extinctions but the sheer decline of plankton at the K-Pg extinction was quite distinct both with the lack of freshwater algal proliferation and the loss of marine phytoplankton diversity . The book Monarchs of the sea focusing on cephalopods goes to suggest this lack of plankton given the size of ammonoids eggs suggests they were likely planktonic was potentially responsible their extinction. I'm sure acidification wasn't good either but they had dealt with that threat earlier with the great dying so I doubt that was the sole factor. Also one really peculiar thing is that for all their beautiful shells we have never found one with soft body preservation unlike nautiloids, there has been a possible shell-less ammonoid which at first seems bizarre but might actually provide the explanation for this lack of soft body fossilization based on what we know about squid and how their adaptation of ammonia as a lifting gas for buoyancy adjustment has rendered them unfossilizable due to PH criteria. If the ammonoids had stumbled onto the same use of ammonia in their shell chambers for buoyancy that would neatly describe why we never see intact ammonites in their shells under Lagerstatten conditions.

Thanks for this explanation! I will never be able to comprehend the staggering amount of time it takes to carry out geological and biological processes. Human lives are just a blink of an eye. It can be brilliant. It depends on us.

Thanks for answering a question I never even thought of. I'm gunna guess they were just in the right place at the wrong time and got lucky.

Thanks a lot!

Praise the algorithm for sending me to this awesome channel today

Thumbs up from a (former) palaeontologist. Clean, simple, and clear. William of Ockham would be proud of you, I think. Thank You. Keep on. Please.

Very interesting video! Could you do a video on feldspar meteorites? I read that such meteorites are responsible for mass extinctions. 😊🦖

I wonder if the thicker shells of the nautiloids might have better resisted acidification in the initial period after the impact. Extinction is rarely a "one thing" deal - usually it's a combination of things, all weakening the organism's survival chances, until the final straw breaks the camel's back - sure that last single factor may be the *proximate* cause, but the ton of straw piled on first made the last one unsurvivable.

That's what survival of the fittest means. When the situation changed, ammonoids longer fit as well as they used to, whereas nautiloids fit better in a pattern that let them persist.

Thank you for lecture, in addition ammonite is the most important macrofossil in late Cretaceous period in biozonation (age determination) which make them better than foraminifera, because it is easly to recognize, wide spread, fast hatching

The level of detective work required to formulate these theories and hypotheses is astounding.

fascinating and fun to learn -- thx lady. i hope your school year went well. are you doing summer school? or will we be getting presumably more videos this summer if you don't? ha. 🐌🐚🐙

Nice!

Thank you

You didn’t mention that from the multitude of Nautiloidea only two genera survived. It’s often not survival of the fittest but the luckiest.

This is a question I've thought about for over a decade, glad the algorithm knew. I guess? Somewhat concerning, glad to be here though.

This was very interesting. I live in Newfoundland and we are very fond of aquatic information. We need to start an online petition to bring back Ammonites! Let's give them another chance😄

Thanks

Great video, very informative and interesting, thanks! Were there any differences in the composition of their shells? If so, chemistry changes in the ocean may also have inhibited shell growth.

Wow who knew this topic would rival optical mineralogy in popularity 😮

"Oh, come on! What's the answer?" If one said that, the person got a proper answer she gave. Yes, unknown is the right one. Those following Geo girl would not expect that, but would be interested in how to deal with the subject. Dealt with it pretty good in my opinion. Series of extinction themes indicate clearly, the approach taken there is very intriguing, in wider scope, reconstructing a whole picture, not only focusing on organisms in question, but also the surroundings, fauna, flora, geological settings & chemical components of the environment then. Curiosity this time around is in the title which is sounds bits provoking. That type of the question, being normally of public interest, is the nastiest, the most embarrassing to paleontologists. "One extinct, the other surviving .." Instead, the basic issue, what's are ammonites & nautilus, is featured. Excellent as usual. On Methuselah's trail by Peter Ward is recommendable (I was young then) in addition.

That's crazy i was literally just wondering this question yesterday, and had found no one talked about it! I think it would be cool if you did one about why amphibians survived, but things such as marine reptiles, dinosaurs, and yes, ammonites didn't! Amphibians seem the most vulnerable to me, am i wrong?

With a shell like ammonoids, the developmental process must have been quite fascinating. I'm not really into evolution, but seeing that process would be very cool

Excellent. I've long wondered why the Ammonoides became extinct. The thicker shells of the Nautiloids would possibly have evolved to withstand the greater pressures at deeper levels of the oceans. This too may have assisted their survival. From your video it seems the predators of neither played much of a role nor any differences in their distribution from equator to pole - unless you have unearthed further information not included in this video...

Great video! 9:38 What are the controversial fossils that led some researchers to suggest that ammonoids survived the K-Pg impact?

Fascinating discussion. Forgive my ignorance, but could changes in surface water chemistry have an effect on their ability to build their shells? If so, perhaps the slower-changing chemistry of deep ocean water provided the nautiloids time to adapt?

Another theory is nautilus (and their even weirder cousins the argonauts) also live in a "goldilocks zone" when it comes to fast moving predatory marine mammals. Basically there's no seals or sea lions where they live.

You can find fossils of both in certain places, there’s a chunk of Ames limestone in Trafford Pennsylvania that has a few of each in it. I have been fossil hunting in Pennsylvanian age rocks around West Virginia and Pennsylvania

It is wonderful that we have nautiloids, those "living fossils", still with us today. Just to think of all the lifeforms, many of which arose later than the nautiloids, that we can now only analyze as fossils, to have those animals whose lineage dates from the early to mid-Paleozoic with us is very fortunate indeed. But they are not thriving. They are down to only a few species, mostly in the western Pacific and the Indian Ocean. Hopefully the stressed status of the current oceanic environment won't mean the end of their existence. Niles Eldredge in his book "Lifepulse" dating from almost four decades ago stressed how groups with less specialized species may have fewer species in general but tend to fare better during periods of mass extinction. A lot of theorizing can be done about why the nautiloids survived the K-Pg extinction while their offshoot relatives the ammonoids didn't, but direct causal effects are hard to pin down and the role of randomness in extinction events can't be discounted.

😮 Ammonoids are so neat! 😊

Some of my favorite critters.

An interesting follow up quetion could be why then did Ammonoids survive the End-permian Great Dying extinction? Many of the extinction causing conditions were similar if not worse to the K-PG extinvtion, and it was more destructive to ocean life overall. It may be that pre-mesozoic ammonoids were not yet as diverse and specialized, so their more generalized lifestyles helped them scrape through in a way that the more specialized creatures of the end-cretaceous could not. It could also just be from a evolutionary roll of the dice or some unknown aspect of the ocean ecosystem that differed between 250 mya and 66 mya. Always more interesting questions that can arise from discussing extinctions.

Do you know what species the image you used on the slide around 4:03 to illustrate the sutures is? I've been looking for an ammonite to get as a tattoo, but I'd like it to be some existing fossil where I could learn a bit about the species itself, and that one is really pretty!

I recommend better microphone! And tnx because of document!

That was good!

One point, you mention that ammonoids may have lived for another 500,000 years after the extinction, and then say that amount of time is geologically inconsequential. Modern humans have only been around for 300,000 years, so it’s more consequential than we are.

Rachel can you make videos on hypothetical scenarios like what if the asteroid that killed the dinosaurs hit today?

Thank you again for a wonderful new Paleo video geo-mommy 😫 If any of y’all are interested in ammonites, i recommend James Witts lecture called Spirals in Time that goes in-depth into this subject and the ecology and biology behind why the Nautiloid body-plan won over the Ammonoid one Here is the link: kzfaq.info/get/bejne/oauZnrmfud2Yiac.html

I feel like i just gained a level in my Jeopardy vocabulary 🙂

_Hello darkness my old friend..._ - Garmin and Siphuncle

This was a particularly interesting episode. I didn't know the difference or that one went extinct and the other survived. Unfortunately the surviving nautiloids are limited to a very small somewhat land-protected area that didn't include any predators but seals have invaded this area now and are munching up the survivors so nautiloids may follow the ammonoids fairly soon. I hope not, they are fascinating and beautiful animals.

Many cephalopods made it past the KPG extinction, and the fossil record is starting to show a curious thing. When seals started to show up in an area, most the cephalopods went extinct. The nautiloids are deeper water animals and seals wouldn't have been eating them.

The Wheel of Fortune, some lose and some win.

AHH yes my favourite cephalopod folk rock group: Garmon and Siphuncle.

Cephalapods are so awesome

I was taught that earlier species had uncoiled shells, which became coiled later on. Can you address that?

Great! But "to help understand future extinction events" 🤔 Or perhaps its actually just really cool and interesting! Especially given that each extinction even is so very different and since the rise of Man and the changes we have made no previous extinction events will ever be the same again!

There might be a stronger critical mass barrier for eggs on the surface than for eggs in the deeps.

the haptics with this video are bugging me so much, great video though

Is there a relationship between ammonoids and ammonia (the chemical)?

Arguably ammonoids were more "evolved" (derived) than nautiloids which is why they were more susceptible to changes.

Location, location, location!

Awesome 👌 We need more females in the Science KZfaq Science education community. High quality content 😊

Great video, thanks! Please pardon my ridiculous comments where I clearly disagree with modern science while appreciating everything people do for advancing our collective understanding. With regard to ammonites, science has greatly overlooked the Hindu sacred stone known as the shaligram. It is classified as an ammonite, however they have not been rigorously studied (due to the religious views of the stones and being found only in the Gandaki River in Nepal near a place called Damodar Kund). These stones are *exceptional.* They frequently have cross sectional openings (along the thin axis) into a chamber where the fossilized shell is considered to have been. In these stones, I have seen the boundaries of one fossil merge *seamlessly* with the boundaries of another as if they were one unit. I have seen hexagonal cross sections where they should be rounded like the shape of a shell. The surrounding matrix of a shaligram can be as intricate and unique as the shapes within the stone. I have perhaps 100 hours of video just simply reviewing the nuances of these stones. This is highly relevant to the concept that ammonites have siphuncles at the boundary of the shell where nautiloids have the siphuncle down the middle. Shaligrams are conclusive proof that geological processes have the capacity of literally forming these structures (and did) without any shell being contained in a matrix, but just with current flows within the matrix. The position of the siphuncle at the boundary of the shell is because there were currents flowing in eddies within the matrix material that shaped the stone. If you look the Gplates EMAG2 map of the Earth, there is an ammonite structure literally under Australia--inclusive of siphuncles and various structures that are reminiscent of those said to be parts of ammonites (gut and buccal mass for instance). Its final chamber is the center of Australia, where its spiral center is near the north coast and its upper boundary reaches the islands north of Australia. There are many examples of fractal structures of ammonites. South of Australia is an island known as Skull Rock. It has an ammonite physically attached to its outer face (upper right side relative to the large opening in Skull Rock itself). This and many other reasons strongly suggest that the K/Pg boundary is an important time in Earth's geological history where a drastic change in the Earth's processes occurred at this time that no longer provided the capacity to produce ammonites. As ammonites such as the one under Australia can be described as being induced by interactions of current flows--namely ones that are colliding under sufficient pressure to induce an eddy between the currents--then it would mean that there was a relieving of pressures that were causing eddies to form to a sufficient degree so that they simply no longer formed. This also would explain their wide diversity--because current interactions are nuanced and can result in many outcomes. For there to be a major pressure release at the K/Pg boundary would indicate that it was not simply an impact (there are 15 potential impacts in literature that I have found at the K/Pg boundary based on stratigraphy and even some by radiometric dating). I know its not the present consensus and has been considered disproven, but Earth expansion models show rapid expansion of the Earth largely began around ~66Ma. Oceans have many indicators of a relationship to this time frame, such as the average age of ocean crust is 64.2Ma overall, 65.7Ma for the Pacific, 69.2Ma for the Atlantic, 60Ma for the Indian ocean. Hydrothermal vents have relationships to this date. Seamount chains both begin at 66Ma (Louisville seamount chain) and end at 66Ma (Mid Pacific Mountains). There are many things that would be purely coincidence from modern interpretations that are distinctly linked to the K/Pg boundary. So there is the potential that the Earth expanded, slowly from ~550Ma-66Ma (accelerating around 100-80Ma) and then entered a rapid phase of expansion around ~66Ma. This would mean that internal pressures under the crust pushing against it to fracture it into continents from a single landmass built up, and built up--inducing more and more eddies across all scales on the planet--until the crust actually broke apart enough for the pressure to be relieved and most of the energy to then be put into forming the ocean floors until a genuine equilibrium was reached between the interior and exterior of the planet. Then the currents were greatly reduced to such a degree that ammonites were no longer induced by swirling eddies. This even ties into chemistry, as it points to a fractal nature that can be studied and relied upon for basis to conclude nuances of atomic structures and mechanisms. I would suggest that nautiloids existed in truth while ammonites just appear so much like them that we have concluded them to be. The dendrites of the ammonites I have seen on shaligrams *without an ammonite present.* Just purely wrapping around the stone itself like waves at its "equator." Fully around the stone demonstrating it is not just a piece of a larger ammonite shell, but instead is truly formed wrapping around the stones. These types of examples are not accounted for in the interpretations modern science has arrived at and would materially change the view if accounted for because they simply cannot be fossils in instances such as that. I have a video titled "Shaligrams: From the Heart" that has these in it (3:27 of the video) as well as many shaligrams that purely cannot be explained by traditional methods and requires additional considerations and amendments of preexisting concepts to be able to account for them as well.