I saw that my friend had “dinosaur sex” on his google search history a lot so I sent him this because I thought he’d be interested.

Do an episode about prehistoric India when the subcontinent was an island before it crashed into Asia.

Two distinct species could actually be sexual dimorphism and we would have no idea

It makes sense that sex of dinosaurs would be hard to distinguish. One being bird and reptile related, without colour patterns and feathers or eggs, theres no identifying features to base any differences on. Adding to this, some species of reptiles are very prone to hormonal changes and genetics designating sex in eggs or amphibians, and the existence of reproduction like parthogenisis.

Grew up on a farm. "Sexing chicks" was bad enough. (To tell male from female chicken chicks.) Do that a few years as a kid, and the thought "sex the dino" is basically a NO WAY!

It’s sometimes difficult to tell the sexes of reptiles to this day, much less from (often incomplete) fossils. One has to be an expert, often probing the cloaca for bumps, counting them for male or female. Those bumps are soft tissue & internal, thus are rarely preserved

Setting aside how cool it is that we can (potentially) tell something like this about a creature that's been dead for over 65 million years, can I just say that I love how well this showcases the scientific process? Someone finds some interesting technique or concept, and backs it up with evidence. Someone else is skeptical, and provides their own evidence as to why. The first person goes out and (maybe?) conclusively backs up their points with brilliant evidence. This is fundamentally what science is about, and I love seeing it on full display here.

Wait! Wait just a second! Are you telling me that the T-Rex in Chicago might be a "boy named Sue?"

If Steve is still alive and watching, we appreciate you too

The museum I intern at here in Wyoming, has the 1st and only T-rex to stay in Wyoming. We don't know if its male or female; the body is small but a tail section is broken and healed over so maybe mated? The femur size is also small. Our rexes name is Lee :)

I was always told that fossils are essentially "casts" of the original bones in rock. I wouldnt think that anything inside the bones could have ever been preserved. Thats amazing!

I love the scientific process so much. It's so exciting when scientists think of new ways to test a hypothesis and potentially learn something new.

Something I'm surprised this video didn't touch on is that we do have other animals we've been able to reasonably extrapolate the sex of! Specifically pterosaurs, which aren't dinosaurs themselves but their closest relatives. Pteranodon is famous for having two different size morphs, the larger of which has a big sweeping crest whilst the smaller one has basically a nub. Considering they had been found together, and all other characteristics of their skeletons pointed to them being the same species, we already had some decent evidence of sexual dimorphism. This is further reinforced by immature specimens of both the large AND small morphs being present, indicating that the small morph itself wasn't just an immature version of the larger morph. Figuring out which is male and which is female specifically is still far from an exact science because of how much dimorphism can vary between species as touched on in this video, but it's fairly universally assumed that the large morph is the male, while the small one is the female. While females can be larger in dimorphic species, males being the larger one is more common among tetrapods, particularly so for males with a display structure just like in Pteranodon. Animals in which females are larger rarely also have display features, and vice versa. Additionally the smaller females seem to outnumber the larger males, which is also consistent with most modern day animals. While there are cases in which females take on multiple males (polyandry) it is much, much rarer than males taking multiple females (polygyny). Males can mate frequently and easily thus have little need to be as selective when choosing a mate, while females need to be more choosy about who they mate with due to the time and resources they have to put into reproduction, so in the majority of animals there's pressure to evolve a polygynous system rather than polyandrous. Again, this isn't universal, but it is by far the more common method of mate selection. Additionally, the smaller females seemed to have wider-set pelvic bones, likely to pass eggs more easily. It isn't reliable as the sole way to sex a skeleton because many species don't seem to have wider hips when you'd think it advantageous, plus it can vary a lot between individuals within a species (including us, hence why archaeologists try to use cultural signifiers such as what a person was buried with to determine sex rather than features of their skeleton). But with everything else in mind it's a pretty safe assumption that Pteranodon's have sexual dimorphism in which males are larger with big crests, while females are smaller with tiny crests.

This is such a great overview of the scientific process, and an awesome video! My favorite channel!

It crossed my mind that _T. rex_ evolved from much smaller ancestors so if it did use those bone deposits it could be vestigial

Love the face-tickling turtles!

I first read about medullary bone from a compilation of _Scientific American_ vertebrate articles that I bought, but I didn't realize at the time that it could be discerned in fossils until much later.

I’m confused. Aren’t fossil bone molecules different from those of regular bone? Like totally different minerals? How is it then possible to compare staining between the two?

Fascinating episode. Well-explained research.

Ugh… I love dinosaurs sooooo much 🦖 never get tired of this!

Absolutely fascinating debate and ace work by Schweitzer and her team! The new paper should have tested the large population sample for medulary bone tissue to see if it matched with the dimorphism characteristics! And always appreciate the mention of thanks for indigenous land and community help!

Will you guys be uploading to your podcast anytime soon?

Interesting that the tissue was still preserved after all those millions of years. I would love to see you guys do a video on the soft tissue that was also found within B-rex and other fossils since

I'm so stupidly excited when a new Eons is posted. Always informative, great art, new ideas.

Love this very interesting content Thank you!!

I always learn from your videos

Happy 200 years of Dinosaurs 🦖 Its been 200 years since Megalosarus was named…

Paleontology is so full of unresolved and troubling questions that causes scientists to argue about.

Oh, this is fascinating!!

It's an interesting question bc well we don't even really know what to base speculation on. As mentioned, many reptile species have larger females. They also do need quite a lot of calcium after laying, so much so that some species can die if they "double clutch" in a season. And then there's some reptiles that are viviparous or oviviviparous. But in any of the cases idk how we'd know for sure that was their method without finding a gravid female. And then there are crocs (yes ik they're a reptiles, but they do it a bit different) and birds.

00:32 THIS CAUGHT ME OFF GUARD

very intresting as always

Here, you’ve read a lot of lame comments. Have a bento 🍱

The picture at 5:54 almost looks like a Magic Eye illusion.

We need more investigation into the egg laying cycles of Emos. 😅

Enjoyed the video! I prefer the slightly longer approach work more details

I LOVE this cutting-edge paleonthology episodes. only PBS Terra brings this for us. thanks guys!

I would love to see a study on the evolution of the humming bird!

But...grandpa said all the dinosaurs are girls...

As always, thank you for your enjoyable & enlightening episodes. 👏🖖

Was listening along and got to the section on the study that theorized the structure was a more general bone disease and I'm like, "Well, can't tell the sex but might have found evidence of dinosaur syphilis." LOL

Thank you for so often acknowledging native land where fossils are found, and where episodes take place. ❤️

I watched you guys back in 2017 i love dinosaurs

Please do an episode on the Livyatan and other macroraptorial sperm whales

Before watching the video, I am guessing they were like birds and had a cloaca

Did Dinos also lay unfertiliezed eggs?

I miss Steve :c

If modern birds are descended from dinosaurs, does that mean they are more related to dinosaurs than modern reptiles are? Also, does that mean that no birds existed when the dinosaurs existed?

Quick question. Since chickens have insane head stability. (Insert that funny bmw commercial) are there any known dinosaurs that had that ability?

If both pterasaurs and dinosaurs both had this special bone tissue, then shouldnt it be an ancetry trait from a common ancestor? Maybe it didnt develop in birds but instead is a relic of fish transitionint to land. fish dont have high calcium bones, so maybe then needed it first to develop proper eggshells? Or maybe it developed a bit later when terrestrial animals became totally free from water and developed hard shells? Maybe we could prove this by looking at mososaur bones. If they have this weird bonestructur even tho they werent terrestial but came from terrestial animals, they just kept the trait?

I love the Eons content and hosts! Love that plug at the end for emonightbk, these ladies are the coolest!

Isn't alluvium always deposited by water? I think material left behind by ice would be glacial till.

This is interesting

Such a nice video ❤❤❤❤❤

That was all so interesting!

Oh, hey, just like birds!

I think most definitely would have a cloaca, but finding an external structure preserved would also be interesting. Do mammals have the same bone differences when pregnant too? Thinking it will take a lot of calcium to build baby bones inside.

Birds are Dinosaurs. It is difficult to overstate the significance of this fact, for palaeontology. Perhaps the most recognisable group of vertebrates, Dinosaur bones line both displays and drawers in every natural history museum, offering endless fascination for children and adults alike. Yet, so much about these creatures is lost to history. Think of how little the bones of an animal resemble the living being they once supported. The colour of their eyes, the texture of their skin, the way they moved, the chemistry of their blood; all gone. We take for granted the ability to discern the sex of living creatures, but this is exceedingly difficult in fossil animals. Anyone who has ever owned a reptile knows the difficulties of discerning male from female. This is because of their lack of external sexual organs, as well as the typically little sexual dimorphism between the sexes of most species. This difficulty is multiplied when looking at (often incomplete) remains of extinct reptiles, like Dinosaurs. Most species of Dinosaur are known only from a single specimen; so we usually don’t even know what the female of an extinct species is supposed to look like! Exceptionally preserved fossils, and ever-advancing methods of studying them, help fill in some of these gaps. But the closest we will ever come to knowing the living anatomy of these amazing animals, is found in their living descendants, the birds. Despite how unique birds are, even among the dinosaurs, many of their anatomical curiosities are deeply rooted in the Dinosaur family tree. These include feathers, wishbones and even the air sacs of their respiratory systems. Well, it turns out the similarities go even deeper. Down to the bone, in fact. Dinosaurs lay hard-shelled eggs; these require extra calcium. In female birds, this calcium is laid down and stored in a unique type of long-bone tissue called Medullary bone. Its presence is an indicator of a sexually mature female, about to lay eggs. This tissue has now been found in multiple Non-Avian Dinosaurs,including a T-Rex.

Neat

its hard to tell the sex of a dinosaur nowadays because they usually don't fossilize while "Doing the deed".

yeah dinosaurs 🤘💯

I wonder how dinosaurs mated?

Bobbi Rex

Ngl I miss the jokes at the end of the episodes 😢

You’re awesome!

I believe Dr.Malcom asked about this in Jurassic Park

I love your presenters.

Egg layers are referred to as "gravid," not "pregnant."

Oh, those are some cool earrings, they aren't amber fossils are they?

....moraine

Steve...

🥰🦖

Why did the dinosaur cross the road ? To ask the chicken who lays the eggs lol😂😂

I absolutely adore this channel. All of the presenters are very charismatic and the storytelling is perfectly crafted and compelling. I really miss your podcast on Spotify!

I would have thought Terminal moraine but could be wrong been a long time since I studied Physical Geography

This episode was well done and....well presented.

I feel like we need to look at more species. We don't know if this applies to all theropods or even all dinosaurs. Regarding function in T-Rex, it is possible that this structure evolved in a smaller ancestor and was kept.

🤙🖤

Michelle has really improved as a host, she’s excellent!

On interesting possibility is that both camps of the discussion are right. Evolution works more often than not by adapting a previous trait (say bones grew out of calcium sacs, or dogs got most of its socializing features by keeping their puppy traits, etc.). Thus, I would not be surprised, if the current medullary bone structure was actually an adaptation of a different feature that the Rex lineage used for something else. After all, the rex are just the previous branch theropods to the lineage that evolved into birds. So I would be inclined to assume that the Maniraptoriformes had some special feature in their bones that they adapted later to enable flights, but probably had the original structure shared with Tyrannosauroidea or even earlier ancestors. It would explain both why it did react to the chemical signature but was not necessary given the bone density for egg laying.

Very interesting video... Love your dress!!!❤❤❤

I just love Michelle’s style! It’s gothy/punk paleontology!

Mature Female Dinosaurs in your area 😏

What happened to the theory proposed a short while ago, that the first lower caudal spine would be reduced or absent (as in female crocodiles) to allow more room for the eggs to pass?

Well, now you've gotten tRICKy again! The larger accretions left behind upon the retreat of glaciers is called moraine alright! "Terminal" at the glacier's furthest reach, and "lateral" at the sides. Alluvium is usuallly the ground down material from beneath the body of it, though some of that may arrive from (upstream of) the remaining watercourse? Apologies for being a pedant though, but it is high school stuff, so where was that enquirer then, hmm?

A (very old) stereotype about people in science, is that they have very little fashion sense. But I wish I had one tenth of the style the people of Eons (any of them) show in each video.

I always get excited when i see Michelle is hosting a video. They're so cool and their presentation style is really friendly and engaging.

Defining the sexes solely by the type of gamete produced is the only taxon agnostic, and technically correct, method of doing so. But don't let PZ Myers know that you did so, because he'll have a conniption over it. 😂

What about Dinosaur STDs?

Sex, sex, sex. Interesting actually.

Dinosaur love and Life is war

I don’t know why we’d need clarification between female aka egg producing and male aka sperm producing dinos as that’s an obvious. Enjoying the subject though and hope these continue

Well have they found Medullary bone from a male bird?

Because cloaca can't be fossilize, idk. that's my guess.

We call them Eskers…. There’s a bunch here in PG.

Bone density?

Is this IA dinosaur?

Scotty is a female while Sue is a male T-rex, so female T-rex are possibly bigger than male.

0:07 This looks very safe!

I saw "femora" in one of those headlines. The other plural, "femina", may have been more appropriate. (It's an r/n noun, though it has no known cognates.)