#ava's journal

[paleobird]

From the Journal of Ava Ostrom

Dinosaurs: A Summary

What IS a dinosaur? Despite their dominance in popular culture, you'd be hard pressed to get a proper answer if you asked a random person on the street this question. Often, 'dinosaur' and 'prehistoric animal' are considered one and the same by many. In truth, dinosaurs are just one of countless lineages of animals that have existed on this planet, but that doesn't make them any less fascinating!

So, what is a dinosaur, really? While I could go into the nitty gritty, explaining specific skeletal features and so on, it's probably best to keep it as simple as possible:

First things first, dinosaurs are a group of reptiles. Prehistoric mammals, amphibians, etc. are NOT dinosaurs.

Second, dinosaurs are of a specific group of reptiles called Archosaurs, the group that also includes crocodilians and pterosaurs.

Third, birds are dinosaurs, full stop. Dinosaurs did not BECOME birds, birds are just the only lineage of the dinosaur family tree that is still around today.

Note that this means many famous prehistoric animals, such as the woolly mammoth, Dimetrodon, pterosaurs, and marine reptiles, are NOT dinosaurs.

That's not to say, however, that dinosaurs were not diverse animals. They were divided into two major groups: the Saurischia and the Ornithischia, named after the general shape of their hip bones: lizard-like or bird-like.

The Saurischia can be further divided, again, into two families: the Sauropodomorpha--made up primarily of the long-necked and often gigantic Sauropods--and the Theropoda, the group that included all the bipedal, primarily carnivorous dinosaurs; modern birds are Theropods.

The Ornithischia was even more diverse: at its most basic, it can be divided into three major families: Thyreophora (the armored dinosaurs, primarily Stegosaurs and Ankylosaurs), Marginocephalia (horned Ceratopsians and thick-headed Pachycephalosaurs), and Ornithopoda-a group of insanely diverse and hugely successful herbivores that came in all shapes and sizes and, most famously, includes the Hadrosaurs, or 'duck-billed dinosaurs.'

Now, I could go on, but I think this is a decent enough summary, and my talons are getting sore. I'll start going into specific species of dinosaurs next time--starting with my favorite!

[ends-of-the-wayward-storm]

Journal Entry ???

As of the time this picture was taken, I was still trying to level my Wonderland world so I could ascend Ava(ria). Of course, just because she's stuck on level 20 doesn't mean I can't still have her on the team I made with people she makes a connection with and have them keep her from getting sniped. :3 So here she is in Liyue, my favorite region!✨✨ (Journal entry is under the cut.)

Jifang asked me if I could run an errand for her in Qingce Village, so that's where I am now. I ran into that guy with the light blue hair again on my way to the address I was given, and he seemed to recognize me from the last two times we ran into each other. We didn't really say much, though. He seemed a little awkward and I'm not that great with talking to people.

I was going to head back to Liyue Harbor right after I finished the errand, but the view on the way out was nice enough for me to stay a bit longer. I know my last teacher would've wanted me to enjoy it.

I should be heading back now since I still have a job to do. But I guess writing in this every now and then still feels nice, even if it's just to get a couple words out. I'm glad my teacher gave this journal to me.

[paleobird]

What Type of Dinosaur Should Ava Write About Next?

Another Theropod

Sauropod

Ceratopsian

Stegosaur

Ankylosaur

Pachycephalosaur

Ornithopod

Mun Answer

Voting ended onSep 26, 2025

[paleobird]

From the journal of Ava Ostrom

Dinosaurs: Borealopelta markmitchelli

Most fossils, unfortunately, are very fragmentary; paleontologists learn very quickly not to get their hopes up that they'll find a complete, perfectly articulated skeleton like you see in movies. Every once in awhile, though, we hit a metaphorical goldmine, and Borealopelta is one of the most famous examples.

The sole specimen of this ankylosaur, discovered in 2011 and named properly in 2017 after being properly excavated and prepared, had almost its entire top half preserved in three dimensions, without any shriveling or compression, including soft tissue impressions. It's believed that the animal died, washed out to sea, and sunk back-first into the sediment, where it was buried quickly enough to be preserved so pristinely.

In fact, scientists were able to acquire fossilized remnants of melanosomes--pigment cells--from the fossil, allowing us to ascertain its general coloration in life: reddish-brown, with a lighter underside that suggested countershading camouflage. This more or less confirms that, despite its large size (a solid 5.5 meters long), armored osteoderms, and impressive shoulder spikes, it was still under risk of predation. We also have evidence of stomach contents: mostly ferns, suggesting a fairly specialized diet.

Unlike Ankylosaurus, which was an Ankylosaurid, Borealopelta was in a sister group called the Nodosauridae, characterized primarily by a lack of a tail club and larger spikes along its body. Borealopelta is also between 110 and 112 million years old, putting it in the Early Cretaceous as opposed to near the end of the period like its famous cousin.

[paleobird]

From the journal of Ava Ostrom

Dinosaurs: Ankylosaurus magniventris

Ankylosaurs are some of the more popular dinosaurs, thanks to their bulky, armored bodies, spikes, and club tails. And, of course, Ankylosaurus itself was the largest and most famous of them all. But there was more to these tanky beasts than just what we see on the surface.

At around 8 meters long, Ankylosaurus (or 'fused reptile,' due to fused bones in the skeleton) was one of the biggest members of the Ankylosauridae, and one of the last as well, as it existed between 68 and 66 million years ago, right before the famous Cretaceous mass extinction that ended the reign of the dinosaurs as a whole. Like all members of this family, it was covered in osteoderms: knobs of bone that were embedded in the skin and acted as armor plating (crocodilians have these as well). Half-rings of bone armor also wrapped around the neck, and even its eyelids were armored, making for a very well-protected animal. Considering it lived alongside Tyrannosaurus rex, such protection was very justified.

Some modified osteoderms formed an impressive club at the end of Ankylosaurus' tail, and the last several vertebrae were stiffened and fused together to make the 'handle' of the club. A single swing of this club would have been devastating, and it's generally believed to have been used for defense against predators. However, evidence in another ankylosaur species, Tarchia, suggests that they may have used their clubs against each other--possibly in territorial disputes, or to fight over a mate.

Ankylosaurus was a generalist feeder that probably ate mostly ferns, low-growing shrubbery (it wasn't exactly tall enough to handle trees), and fruits. There was little chewing involved, so they likely fermented their food in a hindgut, which would explain their exceptionally broad torsos. Various other species in this family may have fed in different ways, allowing for niche partitioning among contemporary species and therefore avoiding unnecessary competition over food.

A final interesting note: a well-preserved fossil of the ankylosaur Pinacosaurus revealed what may be a syrinx--the vocal organ in birds, which is the source of their famously broad range of vocalizations. While ankylosaurs probably didn't chirp like a songbird--they were adapted to hear low frequencies, not high ones--this discovery suggests they may have been very vocal regardless, and if the syrinx evolved in other dinosaur lineages than just birds, it may be surprisingly widespread among other types of dinosaurs as well.

[paleobird]

"I love the Ankylosaur sweep! Might write about two of them. As a treat."

[paleobird]

From the journal of Ava Ostrom

Dinosaurs: Dilophosaurus wetherilli

There are few dinosaurs that have suffered in pop culture the same way that Dilophosaurus has. Michael Crichton's Jurassic Park novel portrayed the animal as not only venomous, but capable of spitting said venom like a spitting cobra. The film adaptation, infamously, doubled down on this by also giving Dilophosaurus an extendable frill and shrinking it significantly in size. While all of this certainly helped Dilophosaurus make a name for itself, it's safe to say that it has been underappreciated for its real value.

First things first: Dilophosaurus was not a small, dog-sized animal. The largest discovered fossil specimen was 7 meters long and, in life, probably weighed close to 400 kilograms--this was a dinosaur the size of a bear, not a dog. In fact, it was the largest theropod of its time in Early Jurassic North America around 186 million years ago; this was well before the truly titanic theropods would evolve.

Dilophosaurus, meaning 'Two-Crested Reptile,' is so named for the distinctive pair of half moon-shaped crests atop its head. These crests were large but thin and probably intended solely for display; they were likely very brightly colored when the animal was alive.

While slender and with a lightweight skeleton, Dilophosaurus was almost certainly not a delicate scavenger as was once suggested; it was active and agile, with a birdlike unidirectional respiratory system that was more efficient than that of mammals, and it may have had a bite strong enough to puncture bone. Its forelimbs, too, were remarkably strong and were likely used for holding struggling prey in place. Considering no other land animal in its habitat at the time got to its size, Dilophosaurus was probably the apex predator of its ecosystem, with no competition as an adult.

Classifying Dilophosaurus has, historically, been a bit of a chore. While there are similar theropods with head ornamentation--such as Cryolophosaurus, Dracovenator, and Sinosaurus--the possibility that these similarities are due to convergent evolution cannot be ruled out. Generally speaking, these animals are all lumped into their own group, the Dilophosauridae, which were fairly basal (aka 'primitive') theropods compared to their larger descendants.

At the very least, we know it's not a Megalosaur--but that's a rant for another journal entry!

[paleobird]

From the Journal of Ava Ostrom

Dinosaurs: Deinonychus antirrhopus

Deinonychus: my personal favorite dinosaur, and one of the most important to the history of paleontology itself. The study of Deinonychus in the 60's was what kickstarted the so-called 'Dinosaur Renaissance,' when scientists began to look at these animals as active, potentially warm-blooded creatures instead of the slow, plodding, archetypical 'ancient reptile' of eons past that dinosaurs were depicted as before.

Deinonychus was a dromaeosaur--known in pop culture as 'raptors,' such as the now-famous Velociraptor. They are characterized by being generally small to medium sized (with some surprisingly large exceptions), bipedal, covered in feathers, and possessing an enlarged, sickle-shaped claw on the second toe of each foot. This toe was hyper-extended and kept raised off the ground while the animal was walking, and this claw is what gives Deinonychus its name, which means 'terrible claw.'

So what made Deinonychus such a big deal, exactly? These days, it's pretty straightforward; indeed, it's more or less the direct inspiration for Jurassic Park's oversized Velociraptors. But at the time of its discovery in 1931, the idea of a small and agile dinosaur just didn't occur to scientists at the time, and it took until 1964, when more complete Deinonychus remains were discovered, that it could be properly described. Not only was this animal clearly active, athletic, and agile, but had skeletal features incredibly similar to those of birds.

Thanks to Deinonychus, the connection between birds and their fellow dinosaurs is unmistakable, and dinosaurs themselves are universally depicted as fast-moving, active, and warm-blooded. They certainly weren't sluggish, dimwitted swamp dwellers!

Deinonychus itself hails from the western United States (with circumstantial evidence of its presence in Maryland) during a large stretch of the Cretaceous Period, approximately 115 to 93 million years ago. At around 3 meters in length, it wasn't a particularly huge animal, and likely hunted smaller animals in its environment. The large sickle claws were like meat hooks, used in a form of prey capture called Raptor Prey Restraint (RPR): essentially, Deinonychus would leap on its victim, pinning them under its weight and digging its foot claws into the animal to maintain its grip. Then, flapping its arms to stay balanced, it would used its jaws to essentially eat the unfortunate animal alive. Fun!

Perhaps the most controversial topic surrounding Deinonychus and its fellows in the modern day is how social they were. Famously, the fossils of multiple Deinonychus individuals were found in association with the skeleton of a large ornithopod dinosaur called Tenontosaurus, which the smaller predators had clearly been feeding on--this seemed to be a common occurrence. Being twice the length and at least three times the weight of Deinonychus, Tenontosaurus had nothing to fear from one of these dromaeosaurs, but what about a pack?

Well... probably not. The sort of cooperative pack-hunting seen in things like wolves and African wild dogs is the purview of mammals, but this is not to say reptiles are antisocial. Indeed, birds can be very gregarious, and even crocodiles--the closest living relatives of dinosaurs--will tolerate one another in decent-sized groups, and have even been observed working together to take down prey to some degree. Deinonychus may not have brought down adult Tenontosaurus (the region's apex predator, Acrocanthosaurus, probably did though), but they almost certainly traveled and lived in at least small groups, feeding together if they found a large carcass that could be shared--the possibility of infighting amongst individuals, and even cannibalism, though, cannot be ignored.