#thyreophorans

Jakapil kaniukura was a basal thyreophoran, the group that led to stegosaurs in the Late Jurassic and ankylosaurs in the Cretaceous. In the Early Jurassic, thyreophorans like Scutellosaurus were small and bipedal, eventually becoming the armoured tanks of later eras.

However, Jakapil lived in the Late Cretaceous of Argentina, at the same time as ankylosaurs on other continents, and its discovery represents a previously unknown lineage of thyreophoran in South America. Though fragmentary, its proportions seem to suggest it was bipedal like the early thyreophorans, and it also had distinct teeth that allowed it to chew, rather than shear leaves. Hopefully we can uncover more information about this strange little armored dinosaur in the future.

Jakapil lived in the Candeleros Formation which, in the Late Cretaceous, was an ancient desert called the Kokorkom Desert. This environment was covered in windblown sand, broken up by oases. Here, the tiny Jakapil would have lived in the shadow of sauropods like Limaysaurus and Rayososaurus, and the giant theropod Giganotosaurus. It would have also lived alongside small theropods like Bicentenaria, Buitreraptor, and the alvarezsaurid Alnashetri, as well as pseudosuchians like Araripesuchus, rhynchocephalians like Priosphenodon and Tika, mammals like Cronopio, turtles like Prochelidella, and frogs like Avitabatrachus.

#Archovember Day 12 - Miragaia longicollum

In the Late Jurassic of Portugal lived a peculiarly long-necked stegosaur, Miragaia longicollum. Miragaia had at least 17 vertebrae in its neck, more than most sauropods! Its fossil was found during the construction of a new road and, unfortunately, the back half of the skeleton was likely destroyed in the process. 13 bony plates and one tail spike were found scattered, so Miragaia’s plate and spike configuration is mostly unknown. Still, its long neck is a distinguishing feature that sets it apart from any other known stegosaur.

Miragaia was long, graceful, large, but more lightweight than most other stegosaurs, at an estimated 2 metric tons (2.2 short tons). Its long neck could have been a means to browse at levels other herbivores weren’t exploiting, and/or it arose due to sexual selection and was used for display. Like other stegosaurs, it may have also been able to stand on its hind legs to reach even higher levels of browse.

Late Jurassic Portugal in many ways mimicked the Morrison Formation of Wyoming, USA. Miragaia would have lived alongside other stegosaurs like its close relative Dacentrurus. It would have also shared space with the ankylosaur Dracopelta, early ornithopods like Draconyx and Dryosaurus, and sauropods like Lourinhasaurus and Lusotitan. It would have been hunted by the European Allosaur, Allosaurus europaeus, and the European Torvosaur, Torvosaurus gurneyi, as well as other theropods like Lourinhanosaurus.

GUYS.....SOMETHING SCARY JUST HAPPENED... LOOK.......

THAT IS NOT FNAF...,, THAT IS A GODDAMN DINOSAUR!

so yeah surprise surprise to those who didn't read my profile or haven't seen my ancient posts, I also do dinosaur stuff but I almost never post it here so why not post it NOW! this is MY blog and I CAN POST ANYTHING!!!!!!!RAAAAHHHH!!!!!!!!!!!!!!!!!!!

Sauropelta - Sean Closson (twitter)

Apologies in advance if today's article is a bit more scatterbrained than some of my better blogposts in the past, but I've been procrastinating writing for a bit and need to get something out.

The larger group of Dinosauria is traditionally split into two main groups: The Saurischians (lizard hips) and Ornithischians (bird hips). The Saurischians include the Therapods (most meat eaters) and Sauropods (long necks), and have been the focus of a lot of my dinosaur discussion on this blog. So today, I wanna highlight a group from Ornithischia, the Thyreophorans.

Miragaia - TheDinosaurMann (twitter)

Thyreophora includes most of what the public would think of as "Armoured Dinosaurs", and much of the uniting anatomical traits are adapted for a thick set body, weight bearing limbs, powerful tails, and a general predator deterring lifestyle. The earliest and more primitive members of this group were more slender, and evolved from a bipedal common ancestor, but the most derived members were the heaviest, spikiest, and well armoured dinosaurs of their time.

Scutellosaurus, an early Thyreophoran

Gabriel Ugueto/Serpenillus (twitter)

One anatomical trait common to all Thyreophorans is the extensive covering of Osteoderms, bony skin protrusions that decorate and protect the backs, heads, and tails of many members. In the Ankylosaur division, this is mostly present as rounded studs and lumps all along the back and sides of the animal. In Stegosaurs, they present as spikes and plates along the back and tail of the animal. Before researching this topic, it never occurred to me that these were analogous structures, but it makes sense these features had ancestral roots.

To best demonstrate the diversity of Thyreophorans, I want to highlight three of the most recent discovered species from across the group.

Bashanosaurus

@ ttorrooo (on twitter)

This Stegosaur was recently found in China in 2015 and described in 2022. Its name means "Bashan-lizard" Bashan being an old name for Chongqing, where it was discovered. Current research places Bashanosaurus as a very primitive member of the Stegosaur clade, and it shares many traits common with Scelidosaurus, a Thyreophoran thought to have evolved before Stegosaurs and Ankylosaurs diverged.

In later Stegosaurs, the back spines had evolved into angular plates, thought to be primarily a display structure. But in Bashanosaurus, the back spines are still very spiky, and parts of its body still preserve rows of spikes on the side of the body, which were reduced to just one spike on the shoulder or lost altogether in later species. It still had the tail spikes, and this seems to be an ancestral trait. It represents a visual clue on how Stegosaurs evolved some of their more derived traits.

Stegouros

@adamworks (tumblr)

This dinosaur was a very derived Ankylosaur discovered in Chile in 2018, and described in 2021. It's name means "roofed tail". Ankylosaurs were traditionally split into two groups, Ankylosauridae, many of which had tail clubs, and Nodosauridae, which were often heavier built, and lacked tail clubs. These groups were mostly from northern continents, and Ankylosaurs from Australia and Antarctica were harder to classify.

The description of Stegouros prompted the creation of a new division within Ankylosauria; Parankylosauria, a group of Gondwana dinosaurs that diverged earlier, and Euankylosauria, which included the Nodosaurids and Ankylosaurids. While the Northern Continent Ankylosaurs were larger, and utilised clubs in their tail weaponry, Stegouros and its relatives were smaller, less bulky, and Stegouros had a sword on its tail. This tail was less mobile, the "sword" formed from several fused vertebrae, but it was still very dangerous.

Jakapil

Gabriel Diaz Yantén/ PaleoGDY (on twitter)

Video version linked here

This dinosaur was a basal Thyreophoran discovered in Argentina across the 2010s and described in 2022. Its name means "shield bearer" in the Puelchan language. Jakapil represents a lineage of dinosaurs that split off from the rest of Thyreophora before Stegosaurs and Ankylosaurs even split. But whereas most of the time you'd think "basal" or "primitive" means from an older time, Jakapil was from the Late Cretaceous, after most of the Stegosaur lineage had died out.

Thyreophorans were mostly heavy set animals, so quadrupeal locomotion was the norm, but Jakapil was an obligate biped; its arms were too small to walk on. It's well muscled jaw and unique skull shape has many palaeontologists theorising it was a basal Ceratopsian, but the advanced osteoderm armour/spikes on the neck, shoulders and down the back concluded it was a Thyreophoran. A very unique dinosaur indeed.

Thanks for Reading

Hi, if you haven't read any of my stuff before, thanks for reading this. This is sort of my dive into amateur journalism. This is not a dinosaur blog, but I do talk about dinosaurs a lot, so feel free to check out the links in my Pinned Post.

Living in Late Jurassic Wyoming, USA, Gargoyleosaurus parkpinorum is one of the earliest ankylosaurs known from mostly complete fossil remains. It was a nodosaur, part of a family of ankylosaurs that lacked club-tails. Gargoyleosaurus would have instead relied on its body armour and sharp shoulder spikes for defense. It was relatively small, reaching 3–3.5 m (9.8–11.5 ft) long and weighing an estimated 300–754 kg (661–1,662 lb). Like other nodosaurs, it was likely a herbivore, swallowing ferns, cycads, and angiosperms, and relying on symbiotic bacteria and gut flora to digest its food.