#Arizonasaurus

[chameleocoonj]

flocking time :)

[knuppitalism-with-ue]

Results from the Flocking #paleostream

Dinocephalosaurus, Enoploura, Achelousaurus and Arizonasaurus.

[ppaleoartistgallery]

Paleostream 2/03/2024

here are this week's #Paleostream drawings!

today we drew Dinocephalosaurus, Enoploura, Achelousaurus, and Arizonasaurus

[veloci-raptor]

Flocking Together

Dinocephalosaurus/Enoploura

Achelousaurus/Arizonasaurus

[confusedhadrosaur]

Day 20: Arizonasaurus babbitti

[saritawolff]

#Archovember Day 20 - Arizonasaurus babbitti

The Ctenosauriscids were a strange group of pseudosuchians who did the whole “sail” thing looooong before Spinosaurus was even a thought. And in the Middle Triassic of North America, the ctenosauriscid Arizonasaurus babbitti was likely an apex predator. As it was closely related to the bipedal Poposaurids, it was probably also bipedal, looking a lot like a miniature, crocodilian form of Spinosaurus.

It is unknown what this sail was used for, but theories about other sail-backed archosaurs can surely be applied to Arizonasaurus. Edaphosaurus’ sail seems to have been mainly used for thermoregulation, while Dimetrodon’s sail may have also been used for display. Ouranosaurus had a sail which may have been a hump used for fat storage. Even some amphibians had sails, such as the temnospondyl Platyhystrix, and it was probably used for thermoregulation. Even some modern day reptiles, like the basilisk lizard, have sails on their backs. So for sailbacks to keep popping up every so often, there must be a reason… and for now, we don’t know exactly what that reason is.

Arizonasaurus would have shared Middle Triassic Arizona with a variety of temnospondyls, dicynodonts, and the rhyncosaur Ammorhynchus.

Arizonasaurus may also be familiar with long-time followers and/or people who participated in the first Archovember. Yep, this is a repeat. But I felt like we really needed at least one super distinct pseudosuchian this year, and I didn’t really do a great job the first time. 😅

[extinctworld-ua]

Arizonasaurus

Arizonasaurus – це архозавр із родини Ctenosauriscidae, відомий із середнього тріасу (243 млн років тому) формації Моенкопі в північній Аризоні. Таксон характеризується великим спинним вітрилом, утвореним подовженими остистими відростками хребців. Типовий вид, Arizonasaurus babbitti, був названий Самуелем Полом Уеллсом (Samuel Paul Welles) в 1947 році на основі кількох зубів і верхньої щелепи, позначених як зразок…

Повний текст на сайті "Вимерлий світ":

https://extinctworld.in.ua/arizonasaurus/

[aberrantologist]

Doodles from today's flocking paleostream featuring Dinocephalosaurus, Enoploura, Achelousaurus and Arizonasaurus Iced Tea.

[quark-nova]

Why crocodile-line archosaurs are cooler than you think

Pseudosuchian evolution is like really, really underrated. Like people learn a version of "crocodiles have been around for 200 million years" even though pseudosuchians have a super interesting and diverse history. Some forms even converged on the "primitive dinosaur" body plan, despite not being dinosaurs at all!

In rough order of divergence:

Desmatosuchus, an aetosaur

Arizonasaurus, a poposauroid

Shuvosaurus, another poposauroid (not a dinosaur!)

Postosuchus, a rauisuchid

Terrestrisuchus, an early crocodylomorph

Neptunidraco, a thalattosuchian

Baurusuchus, a sebecosuchian

Chimaerasuchus, a notosuchian

Simosuchus, another notosuchian

Anatosuchus, a crocoduck notosuchian

Yacarerani, yet another notosuchian

While bird-line archosaurs are fluffier, and have been much more widespread since the Jurassic, pseudosuchians displayed a much wider range of adaptations than we gave them credit for - from fully aquatic thalattosuchians to small terrestrial, herbivorous, armored notosuchians!

[jurassicjoowan]

Monstrous little Arizonasaurus

While it might be confused for Dimetrodon, this Triassic menace is more alike a proper reptile, and built much more lizard-like than Dimetrodon. This style is starting to grow on me, the bold lines and details make me adore drawing these prehistoric beasties.

[sinosauropteryx--prima]

Sailed Animals

(Sailed animals and their relationships. Art by: Platyhystrix - Gabriel Uguento, Dimetrodon - Rob Soto, Edaphosaurus - Sean Closson, Arizonasaurus, Lotosaurus - Nobo Tamura, Spinosaurus - Liam Elward, Ouranosaurus - Scott Reid, Amargasaurus - Sergey Krasovskiy)

Okay, what I actually wanted to do, was write something about the Permian, and I will be doing that at some point - however, I got side tracked by Dimetrodon and Edaphosaurus and their sails, so here we are.

You see, I‘m a big fan of convergent evolution and especially when the evolution converges to some very specific and bizarre feature that we don‘t fully understand, like big sails on the backs of animals.

As you can see in the picture above, sails have evolved independently from each other many times. Some of the earliest instances come from the late Carboniferous and early Permian and include the amphibian Platyhystrix (I had no idea that there were sailed amphibians, that‘s so cool) and of course the famous carnivorous Dimetrodon and its plant-eating cousin Edaphosaurus. Edaphosaurus and Dimetrodon are often mistaken for reptiles or even dinosaurs. They were neither, but instead they were synapsids, the same group that includes us mammals.

The next time we see sails is during the Triassic in the crocodile-related Pseudosuchians, like the carnivorous Arizonasaurus or herbivorous Lotosaurus. I‘m not entirely sure, if the sails evolved only once in this group, or multiple times, because it is hard to find information on that (I really wish those croc-cousins would get the same attention as dinosaurs).

But speaking of dinosaurs: They of course also had sails. Most famous for it is Spinosaurus and its relatives, but other groups of dinosaurs also evolved sails. Those included the sauropods (the long-necked giant herbivores) like Amargasaurus (well, maybe?), as well as the Ornithopods (duck-billed dinosaurs and their relatives) like Ouranosaurus.

Now you might think that we have a clear lack of sailed animals at the moment, but don’t worry: there are still animals with sails! And somehow I was completely unaware of this until I started looking into it. We still have the Crested Chameleon, some species of basilisks, sail-fin dragons and the sailfish (although from what I understand its sail works differently then the ones of the lizards).

The sails of all these animals are made up from long extensions of the vertebrae. It is assumed that those bones were covered in tissue, spanning open a sail. We can be pretty certain of this, because there have been fossils found, where the bones had broken and then healed back together while the animal was still alive, clearly showing that they must have been held in place by something (Rega et al, 2012).

(skeletons of Dimetrodon, Ouranosaurus and a bison, Bailey 1997)

For different animals these bones can look very different though: For the synapsids like Dimetrodon they were very thin, while they were thicker and flatter in dinosaurs. In that way, they looked a lot more similar to the vertebrae of modern humped animals like bisons. This is why in the 90s there were some suggestions that those dinosaurs didn‘t have sails, but instead had big humps on their back for energy storage or maybe for insulation to keep a constant body temperature (Bailey, 1997).

The idea never really caught on, but we did this amazing illustration of a humped spinosaurus out of it. I know, we‘ve probably all seen our fair share of Spinosaurus reconstructions, but I have never seen a chonky one, and I don‘t know how to feel about it.

(humped Spinosaurus, Bailey 1997)

The big questions that remains is of course: why sails? what were they good for? The most common answer you get is either display or thermoregulation.

The sails being a display structure is a very intuitive answer. If you‘re carrying around a giant billboard-like structure on your back, it would only make sense to advertise something on it. You could use it to impress the opposite sex with fancy colors, intimidate rivals because it makes yourself look a lot bigger or signal to other animals that you are the same/a different species.

One thing that I always think about, but never see mentioned, especially in the case of the herbivorous sailed animals, is mimicry. Edaphosaurus and Dimetrodon lived at the same time, so could it not be, that Edaphosaurus had sails to make themselves look like big scary Dimetrodons to keep other predators away? Similar to how we have many harmless insects pretending to be wasps today? It would of course not explain why Dimetrodon had a sail, but it could give the herbivores a reason to have one.

The other big reason for sails is thermoregulation. Especially cold-blooded animals could have used their sails like solar panels, pointing them towards the sun and collecting heat (Bramwell & Fellgett, 1973). Alternatively, the sails could have been used to cool the animal down by positioning them in the direction of winds (Bennett, 1996).

The only problem with thermoregulation is, that its viability depends on whether the animals in question were endothermic or ectothermic (warm- or cold-blooded). And for pretty much all the sailed animals this is a heated (pun intended) debate.

(Airflow around an Edaphosaurus, Benett 1996; Can I just point out that this graph, as well as the chonky Spinosaurus were part of actual peer reviewed publications? I do chemistry irl and I‘m a bit jealous that in the papers I write I never get the chance to draw dorky looking synapsids)

Now that we‘ve discussed the reasonable well accepted explanations for sails, let‘s get into some more outlandish ones. Maybe Dimetrodon used its sail to „camouflage among reeds while [it] waited for prey, or as an actual boat-like sail to catch the wind while the animal was in the water“, as stated in multiple papers. I tried to hunt down the original source for this, but the idea comes from a Book by Romer and Price from 1940, and unfortunately I don‘t have access to it. Honestly, I would love to know if they had any actual reasoning for it or if they were just throwing ideas around, because the image of a Dimetrodon floating around on the surface of the water and getting pushed around by winds sounds ridiculous. Similarly, having a giant structure on your back, just so you can camouflage it to look like the background seems like a lot of unnecessary effort. Surely you could just not have the giant structure and it would have the same effect.

For Spinosaurus, there is the idea that they might have used their sails to shade the water while hunting, like a heron bird. I had never heard that before, but I find it a bit strange. Wouldn‘t that mean, that they had to catch fish at a weird angle towards their side? Seems uncomfortable. Of course there are also many ideas that the sails might have helped with swimming or whatever, but I don‘t want to get into the Is-Spinosaurus-aquatic-debate. I‘m pretty sure most of the papers about it would be outdated anyways and the ones that aren‘t will be in approximately 20 minutes.

For the sauropods, the “long-necks“, like Amargasaurus, even less is clear: It is even debated whether the spines on their necks formed sails or horns. If they had horns those might have been a defense structure or just for display. If they had sails - well, then it‘s the same questions as for all the other weirdos.

So yeah, overall, sailed animals were pretty weird, and there is still a lot to learn.

Also “sail“ doesn‘t sound like a word anymore.

[makairodonx]

Dinocember Days 26 thru 31

From top to bottom: Mammuthus primigenius, Megalosaurus, Yutyrannus, Suchomimus, Arizonasaurus and Rebacchisaurus

[animalesdownloaddescargarmod]

Pseudosuchia ...............................................................

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[dinodanicus]

Some dino character sketches for recent commission I finished.

[2nights2remember]

Arizonasaurus having a drink (Mid Triassic, colourised)

[saritawolff]

Oof, November is already one week away. This year went so fast…

In any case, this means it is time for another Archovember!

If you’re new here, this is my version of Draw Dinovember that I started doing four years ago to challenge myself to draw not only dinosaurs but other Archosauromorphs that I have less practice with. It usually features a somewhat even mix of dinosaurs, pterosaurs, pseudosuchians, and a handful of oddball outliers.

Anyone can feel free to join in! I will be most active on my Instagram (SaritaPaleo), sharing art of the featured species for the day in my story, including that of anyone who joins in and uses the tag(s). But you can certainly post any of your submissions here too! The animal prompt for each day should be posted on or after their specific day, but can be drawn at any time. You can also join in at any time and don’t necessarily have to draw every animal. The point is to have fun and learn about some interesting prehistoric critters!

In case the graphic is hard to read, here is the list:

1. Your Choice!

2. Dino - Qianzhousaurus sinensis

3. Ptero - Hatzegopteryx thambema

4. Croc - Mahajangasuchus insignis

5. Other - Yarasuchus deccanensis

6. Dino - Regaliceratops peterhewsi

7. Ptero - Dearc sgiathanach

8. Croc - Carnufex carolinensis

9. Other - Doswellia kaltenbachi

10. Dino - Ceratosaurus nasicornis

11. Ptero - Batrachognathus volans

12. Croc - Sebecus icaeorhinus

13. Dino - Lambeosaurus lambei

14. Other - Proterosuchus fergusi

15. Ptero - Ferrodraco lentoni

16. Dino - Shuvuuia deserti

17. Croc - Shamosuchus djadochtaensis

18. Ptero - Caviramus schesaplanensis

19. Dino - Mamenchisaurus sinocanadorum

20. Croc - Arizonasaurus babbitti

21. Other - Smok wawelski

22. Dino - Kentrosaurus aethiopicus

23. Ptero - Sordes pilosus

24. Croc - Burkesuchus mallingrandensis

25. Dino - Pachycephalosaurus wyomingensis

26. Other - Chanaresuchus bonapartei

27. Dino - Animantarx ramaljonesi

28. Ptero - Quetzalcoatlus lawsoni

29. Croc - Batrachotomus kupferzellensis

30. Dino - Concavenator corcovatus

(Also, for new paleoartists: as a heads up when looking for refs you will come across David Peters. It is ill-advised to use any refs from the websites “pterosaur heresies” and “reptile evolution” as all those skeletals come from him and his own personal imagining of the tree of life and are usually pretty innacurate. If you have any trouble finding accurate references, I am more than happy to share the ones I’ll be using!)