#ctenosauriscidae

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…

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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.

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.

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.

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.