Pachycephalosauria

The Pachycephalosauria is one of the most prevalent and successful clades of ornithischians in the *New Dinosaur's* Holocene, their success even rivaling their other ornithischian relatives such as ornithopods and ceratopsians. Examples of the pachycephalosaurs' diversity can be observed in various families, most notably the semi-aquatic kappacephalids and some of their relatives.

## History

Like with ceratosaurs, pachycephalosaurs have an obscure history, with the oldest known member of the clade being the species *Sinocephale bexelli*—originally thought to be be a species of the potentially dubious genus *Troodon*—which dates back to 92 mya. Although not as diverse as the other ornithischians during the Late Cretaceous (only having one family that contains 16 taxa, with 1 other taxa being outside of the family), during the Early Paleocene, they began to diversify into many new forms, especially in North America where they reached their peak of diversity later on. The Late Paleocene is where the Kappacephalidae family first arose in Asia, being descended from a species of Asian pachycephalosaur and specializing to feed on aquatic plants while still retaining some adaptations for feeding on terrestrial plants, the Kappacephalidae family being notable amongst others for their semi-aquatic lifestyle. There were also several other offshoot families which will be discussed later on in this page.

## Kappacephalidae

Kappacephalids are medium-sized pachycephalosaurs which are known for their semi-aquatic lifestyle and diet which consists mostly of aquatic plants, they're most commonly found in the swamps, rivers, and forests of Asia, with some species even extending their range into the Asian part of Australasia, with its tropical jungles and quagmires providing an abundance of food for the kappacephalids to feed on. Kappacephalids are named after the Kappas of our universe's Japanese folklore due to their heads resembling that of a Kappa's—especially with the spikes surrounding the kappacephalids' dome heads resembling the hair surrounding a kappa's bald head—not to mention both being semi-aquatic as well. Most kappacephalids are social pachycephalosaurs, living in groups of 5 to 40 individuals in most species, with the largest amount of individuals in a group being 65 individuals in the Longtail kappa (*Kappacephale mirabilis*). These groups usually consist of one alpha male, two to six other males, and the rest being females and their offspring. While most kappacephalids are predominantly herbivorous, there are some exceptions such as the Fishing kappa (*Kappacephale piscivora*) and the Southern kappa (*Kappacephale notocephale*)—the Fishing kappa being primarily piscivorous and the Southern kappa feeding mostly on both aquatic and terrestrial insects.

### Kappacephalinae

By far the most diverse subfamily of kappacephalids, comprising a total of up to 61 known taxa (12 of them being extinct), the Kappacephalinae accounts for more than half of the diversity of the pachycephalosaurs—making them some of the most diverse dinosaur groups in the *New Dinosaur's* Holocene, rivalling the diversity of fellow ornithischians such as the ornithopods and ceratopsians. The list of kappacephalines below are only a fraction of the diversity of the subfamily, and are only to name just a few as there would be far too many taxa to discuss.

#### Common kappa (*Kappacephale vulgaris*)

Like with what their names state, Common kappas are the most common species of kappacephaline, being found from Asia to some parts of Australasia, most commonly in damp and tropical environments. They can be seen bathing in large bodies of water similarly to the hippos of our universe, and diving in those bodies of water to feed on aquatic plants - able to hold their breath for about 20 minutes before having to resurface. When a predator approaches the group of Common kappas, one of the kappas will signal the others by producing loud calls that may sometimes intimidate smaller predators, with the other kappas noticing the warning call they quickly get out of the body of water and run as fast as they could to escape the predator. Despite being some of the larger taxa of kappacephalids at a length of 3.1 meters (10.1 feet) and a weight of 160 kilograms (353 pounds), they are quite fast runners, capable of running at a speed of 51 km/h (32 mph), making them able to easily escape from any predator in a chase.

#### Colossal kappa (*Kappacephale giganteus*)

The Colossal kappa as you could tell from its name, is the largest species of kappacephalid, boasting a length of 7 meters (23 feet) and weighing as much as 1,400 kilograms (3,086 pounds). They're also unusually bulky for kappacephalids, as well as having the thickest skull out of any kappacephalid that could cause a terrifying amount of damage when hit against something, the thickness of the skull is also useful for protecting the skull from being crushed from being rammed by another Colossal kappa. Unlike most other kappa species, when approached by a predator, the Colossal kappa would instead roar at the threat in order to intimidate it away, if it's unsuccessful, then the Colossal kappa will ram against the threat causing tremendous amounts of damage, mortally wounding the predator. Much like other kappacephalids, Colossal kappas lived in groups, usually consisting up to 10 individuals. When a group of Colossal kappas encounter another group of Colossal kappas, their leaders will battle the other group's leader by ramming each other on land while the others observe while bathing in bodies of water—these battles are likely to cause major injuries and even sometimes death from either infection or blood loss. During the dry season, Colossal kappas would actually congregate with other groups of Colossal kappas rather than fighting them, and migrate to an area with an abundance of vegetation for them to feed on, you may expect to see enormous herds of Colossal kappas numbering up to 100 strong moving across the woodlands of Asia in search of food, and if you do see such occurence, it is truly a remarkable sight to behold.

#### Yellow-throated kappa (*Kappacephale xanthochenius*)

Yellow-throated kappas are small kappacephalines which have a yellow mandible and neck which are exclusive to males using these bright colors for attracting potential mates, hence their name. They're also rather bizarre among other kappacephalids, as they seem to prefer terrestrial plants more so than aquatic plants, and also are more commonly seen on land rather than on water—although when they're threatened by a predator, they would quickly run and dive into water to obviously avoid being eaten—and since these colorful kappacephalines are capable of running at a top speed of 64 km/h (40 mph), they could easily escape from most predators' grasps, even when bodies of water are far away from the Yellow-throated kappas.

#### Fishing kappa (*Kappacephale piscivora*)

A rather unusual species of kappacephaline, the Fishing kappa is primarily piscivorous unlike other kappacephalids which are mostly herbivorous, preferring to feed on small to medium-sized fish and avoiding larger ones. Its dentition appears to be adapted for this unusual diet, with the back-teeth being specialized for holding its slippery prey without letting it go, and its front-teeth being serrated in order to slice its prey apart into smaller chunks that are more easier to swallow. While scientists haven't figured out why its piscivorous diet has evolved, the most likely and common theory is that it evolved as a result of niche partitioning, in order to avoid competition from other herbivorous dinosaurs and also other kappacephalids. Fishing kappas, like most other kappacephalids, are social creatures, and would usually live in groups of up to 12 individuals, the majority of which consist of females and their offspring—much like the groups of other kappacephalid taxa. Interestingly enough, it is not the males who find food for the group, rather, it's the females. While they go underwater to find fish to feed their offspring and the rest of the group, the males take care of the offspring while the females are hunting. Sometimes, smaller groups of lone males will take advantage of the young Fishing kappas' mothers gone out for hunting and try to kill the young in order to mate with the females, however the males of the larger group will protect the offspring by fighting the lone males, these battles could result in major injuries as the Fishing kappa's sharp teeth can inflict serious wounds, but even with one of the sides winning both would inevitably sustain injuries that would probably lead to infections, resulting in some dying.

#### Holtz's kappa (*Kappacephale holtzi*)

The Holtz's kappa, also sometimes known as the Indian kappa, is a large kappacephaline with a relatively large and robust skull, that was named in honor of the paleontologist Thomas Holtz. Attaining a length of up to 5.8 meters (19 feet) and weighing up to 880 kilograms (1,940 pounds), the Holtz's kappa is one of the largest kappacephalids. Although thought to have been related to the Colossal kappa, further genetic studies have shown that the Holtz's kappa is more closely related to the far smaller Yellow-throated kappa. The Holtz's kappa is quite common in the forests of South Asia, particularly in India where they gather in groups of up to 25 individuals, bathing in large bodies of water while diving to forage on aquatic plants. Holtz's kappas have the most extreme sexual dimorphism among the genus *Kappacephale*: males weigh 3 times more and are longer than the females and are more brightly colored, whereas the females are much smaller and are more blandly colored as expected.

#### Grey kappa (*Kappacephale orientalis*)

A small species of kappacephaline, the Grey kappa is comparable in size to the Yellow-throated kappa, albeit being slightly smaller at a weight of 11 kilograms (24 pounds) as opposed to the Yellow-throated kappas which weigh over 18 kilograms (40 pounds). They also appear to have a skull size which is smaller than other kappacephalids of a similar size, but besides that their overall morphology and physiology are very similar to that of the Common kappa. However, Grey kappas appear to be much more social in comparison to other kappacephalids, taking care and playing as well as bonding with others of their groups, and even congregating with other Grey kappa groups in certain situations. What's particularly interesting with the Grey kappas are that females often take care of other females' offspring during their absence, behaving as if they were the offspring's mothers, unlike other kappacephalid mothers which aggressively protect their own offspring when approached by another female.

### Odontorhamphinae

With their relatively long serrated beaks and comparatively small domed heads, the odontorhamphines may not seem like your average kappacephalids, but indeed they are a subfamily of true kappacephalids as suggested by DNA analysis. The two species of odontorhamphines are more commonly known as the bunyips, but although the name "bunyip" translates to "devil" or "evil spirit", the odontorhamphine bunyips are far less evil than what their names imply them to be, and one species is in fact incredibly docile towards humans.

#### Lesser bunyip (*Odontorhamphos rufus*)

Lesser bunyips are one of the two species of the Australian genus *Odontorhamphos*, known most prominently as the bunyips. Although the name "bunyip" translates to "devil" or "evil spirit", the *Odontorhamphos* bunyips are far less evil and in fact, incredibly docile. They tend to bathe in swamps, lakes, and rivers in large numbers, with some catching fish to feed on them with their long serrated beaks belonging to the bunyips' emu-like head. During the mating season, instead of ramming each other using their domed heads, bunyips instead use their serrated beaks to bite each other to try and inflict wounds, which is why their domes appear to be much smaller than in other kappacephalids. In fact, their bizarre physiology lead scientists to believe at first glance that the bunyips weren't kappacephalids, but DNA analysis proves that they're indeed kappacephalids belonging under the subfamily of Odontorhamphinae. Lesser bunyips are obviously the smaller species out of the two bunyip species, at a length of 2.1 meters (7 feet) and weighing 69 kilograms (152 pounds). Lesser bunyips also possess a beak longer than that of the Greater bunyip's, which are specialized to catch their slippery fishy prey.

#### Greater bunyip (*Odontorhamphos ingens*)

The largest out of the two bunyip species, the Greater bunyip attains an impressive length of 4.2 meters (14 feet), and weighs an average of 159 kilograms (350 pounds). Greater bunyips have an extreme example of sexual dimorphism, as males are usually twice the size of females both in length and weight, with the females being comparable in size to the males of the Lesser bunyip species, and as expected, males are much more colorful than the blandly-colored females. Greater bunyips are less social than their smaller relatives, often living in small groups of up to 6 individuals. Due to their territorial tendencies, when a group of Greater bunyips encounter another group of Greater bunyips, both groups will battle each other, using their serrated beaks to bite and inflict injuries on each other. Most of the times even the offspring will get involved in the fight, and most of them are usually killed during fights like these. Recovering from such fights is a very slow process that will take months or even in cases where nearly all individuals of the group have died, several years. Indeed, it is a brutal battle for survival for the Greater bunyips.

#### Southern parappa (*Baturocephale armstrongi*)

Southern parappas, also known as Southern timber kappas, are a medium-sized species and one of the three species of the genus *Baturocephale*, and also one of the three species belonging under the subfamily of Baturocephalinae.