#ctenosauriscidae

[confusedhadrosaur]

Day 20: Arizonasaurus babbitti

[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/

[alphynix]

Weird Backs Month #14 -- Arizonasaurus

(If you’d prefer a more conventional interpretation of this one, I drew a scaly version about a year ago.)

Arizonasaurus is the only ctenosauriscid known from substantial remains -- from Arizona, USA, as its name suggests -- dating to the Middle Triassic (~243 mya). At about 3m long (9′10″), it was probably an apex predator within the local ecosystem.

It’s been a while since I’ve fuzzed up a stem-croc, so let’s get speculative today and talk about the possibility of crocodile feathers.

Fuzz is very likely to be ancestral to all dinosaurs at this point, and since there are also similar hair-like structures in their sister-group the pterosaurs it might go back even further -- and modern crocodilians have what seem to be deactivated feather-forming genes. It’s not too much of a stretch, then, to consider the potential for some sort of fluffy covering being present in the crocodile-line of the archosaurs, too.

There are also no known skin impressions for any of the early croc-relatives, and considering how varied and diverse they were -- some even resembled dinosaurs so closely they were initially mistaken for ornithomimosaurs -- they could very easily still surprise us.

[alphynix]

Weird Backs Month #13 -- Hypselorhachis

Hypselorhachis lived during the Early-Mid Triassic of Tanzania (~247-242 mya). Although only known from a single vertebra, it has enough similarity to the sailbacked stem-crocs to be tentatively classified as a member of that family. Any estimate of its size is also going to be very speculative as a result, but based on its relatives somewhere in the region of 3m long (9′10″) seems likely.

The ctenosauriscids were some of the first archosaurs to spread across the globe, with species known from Africa, Asia, Europe, and North America over a period of about 10 million years. Despite this wide distribution, substantial fossil remains are incredibly lacking and there’s still a lot we don’t know about them.

[alphynix]

Weird Backs Month #12 -- Ctenosauriscus

The sailbacked synapsids all died out by the mid-Permian, and it wasn’t until the Triassic that elongated vertebrae came back into evolutionary fashion -- but in the archosaurs this time, as they rapidly became the dominant land vertebrates in the aftermath of the massive Permian-Triassic extinction.

Ctenosauriscus was a poposauroid stem-crocodilian living during the Early Triassic of Germany (~247 mya), making it one of the very earliest members of the group. Known from a fairly complete sail and a few other small fragments, it's estimated to have reached lengths of up to 3.5m (11′5″).

Its large sail was once proposed as a sort of shock-dissipating system for the physical stresses of walking bipedally, but this is now considered unlikely.

It was probably quadrupedal instead, especially since the the sail would have shifted its center of gravity towards the front of its body -- too far forward for bipedal locomotion to be particularly viable. In the absence of limb bones, though, we don’t know for certain.

[alphynix]

Arizonasaurus babbitti, a 3m-long (9′10″) sailbacked poposauroid from the Middle Triassic of Arizona, USA, about 243 million years ago. Despite looking very much like a retro Spinosaurus, this animal was actually a member of the pseudosuchia -- the crocodilian-line archosaurs.

The limb bones of Arizonasaurus haven’t been found, so it’s not clear whether it was quadrupedal or bipedal. I’ve shown both possibilities here.

Sailbacks formed from elongated vertebrae have convergently evolved multiple times since at least the Permian, also known in fossil temnospondyl amphibians, synapsids, and many different dinosaurs. Some modern reptiles even sport similar sailbacks, including chameleons and sailfin lizards.

Just what these sails were for is still a subject of debate. Although the classic explanation for them is body temperature control, it’s not clear how useful they actually were for this purpose -- and no living species seem to use theirs for thermoregulation. They may instead have simply been very effective visual display structures.

[archosaurophilia]

The magnificent, sailed back of Arizonasaurus babbitti. As you might have noticed, I went on a little croc-line archosaur kick there for the past few posts. Hopefully this remains a trend.