Terrarcaulia

**Terrarcaulians** are a clade of celernantids that are alive today.

## Evolution and taxonomy

Terrarcaulians are the basalmost clade of the terrarmians, also known as the "second wave of terrestrial celernantids". Terrarmians first evolved in the Scelusian, some 194 million years ago, evolved from small ambulosepculid-like celernantids, with armor on their back and bug-like eight limbs. They eventually crawled onto land and became air-breathers. Terrarcaulians themselves are part of the sole surviving lineage of native terrestrial celernantids in Terra Septentrionis, and diverged from each other in the Variagene, 130 million years ago. Terrarcaulians are a sister clade to the larger Brevisurisupia clade, which originated in the late Scelusian, 157 million years ago, in the southern continents. Terrarcaulians have a few species residing in the northern continent, with Terrarmis being the basalmost. The largest clade of terrarcaulians includes the dergol and the mud stalker, and together they form the Dergolia clade, which originated in the late Compsogene, some 66 million years ago, just before Terra Septentrionis started moving slightly more to the south to end the long-lasting glacial period it was passing through.

Terrarmia (194-0)

* Terrarcaulia (130-0)
	+ Terrarmis
	+ Dergolia (66-0)
		- Dergol
		- Mud stalker
* Brevisurisupia (157-0)

## Characteristics

Terrarcaulians are the basalmost terrarmians alive today. They present various characteristics that allowed them to better withstand the life on land and the new environments they were facing. The mouth of the early terrarcaulians was composed of three proboscis, being the lateral proboscis, basally, useless for the consumption of food. Eventually these were repurposed as graspers in the case of Terrarmis, or disappeared in modern dergolians, though the disappearance of the lateral proboscis in the dergol and the mud stalker seem to have occured independently however. Terrarmis has a central proboscis that opens with a small membranous net to grab objects and food. Dergols evolved a very long retractable proboscis that ends with a beak, that is used to fastly catch and hunt polyspeculates, and even used as a simple defense against predators, biting their skin in hope that they will get away. The proboscis of the mud stalker is a retractable "spear", it has a hardened and sharp tip to catch small aquatic fauna. The mud stalker, however, has a simple hyoid jaw that, with the help of the rostrum, has batteries of sharp teeth to help grind and chew the meal, before the small pieces are swallowed by the small proboscis. The eyes of the terrarcaulians are basally simple compound eyes. They only became slightly more complex and focalized with dergols. The presence of external armor was something in the first terrarcaulian, however, however, they slowly lost their use. Many, like the terrarmis and the dergol, have what was once external armor plating, burried in their dorso with skin. The mud stalker has a row of 12 external dorsal plates at the back, split between the soft dorsal fin, a remnant of its larval aquatic stage. The limbs of the terrarcaulians are also differently arranged. The first terrarcaulians had eight limbs, but repurposed them in different manners. One of the most notorious, that shares the group, is the attachment of the first pair of limbs to aid in the formation of a feathered gill agglomerate that helps their aquatic larvae to breath. These eventually become reduced, vestigial or disappear altogether in adults, which no longer require them to breath out of the water. Terrarmis repurpose those for display, as the arms are attached to a large buff of white feathers, no longer used for breathing, now just used to attract mates. They even may color them with berries, blood and dirt, to make them more visually appealing, a sign that terrarcaulians have color vision, like many other celernantids. The second pair of limbs has been used repeatedly for walking. Terrarmis and dergols are bipedal, with the former having lost the two last pairs of limbs, while the latter having them very small to perform any form of locomotion purposes. This bipedal stance, however, seems to have evolved independently in both species, and the mud stalker uses all three last pairs of legs to walk on the swamps. Terrarcaulians largely have a warm-blooded metabolism, in part because of their "feathery" integument. Terrarmis resembles how basal terrarcaulians looked like, completely covered in insulating integument to allow them to survive the cold conditions that Terra Septentrionis has suffered. Dergolians have, however, a largely naked skin, a result of the warming conditions that were arising. They still retain some filaments in their respiratory orifices and, in the case of the mud stalker, they are found in the tips of the legs to sense underwater vibrations. The respiratory orifices of the terrarcaulians are also organized differently. Usually they breath through gills, covered in feathers, as aquatic larval young, but they either loose them, or replace them by simple vertical or dot-like orifices. These major gills are located at the front of the second pair of limbs. They also have dot-like orifices located further behind the body, but those are reduced and serve an aditional purpose in breathing. Dergol have lost those altogether.

The size of terrarcaulians is variable. Dergol, for example, is a large 2,5 meter long beast, while the largest is the mud stalker, with up to 6 meters tall, and 3 to 4 meters long.

## Distribution and habitat

Terrarcaulians are the only surviving group of a basal and ancient lineage of terrarmians that only survived in the isolated Terra Septentrionis. Due to their insulating feathered pelts, the first terrarcaulians were the only native terrestrial celernantids to survive, and there they evolved in isolation. Currently, they try to avoid the fully snowy areas. Terrarmis lives in the temperate jungles and subpolar woodlands. The dergol prefers the arid drylands, steppes and deserts. The mud stalker is capable of living much more to the north, in cold and temperate swamps.

## Diet

Terrarcaulians are carnivores or omnivores. They usually tend to have a very rudimentary chewing mechanism, therefore, for the grinding of their food, they often consume stones so that they can use them to grind the food in their stomach. Terrarmis feeds on fruit and insect-like creatures, using their central proboscis, like all other terrarcaulians. Dergols are largely herbivores, but they usually hunt the mobile polyspeculates that they feed on, with their long retractable proboscis. They may sometimes eat small dispeculates. The mud stalker is a carnivore, sensing the vibration of underwater fish-like creatures, through its sensitive hairs in the legs. It will eventually shoot its spear-like proboscis to spear the prey and eventually use its hyoid jaw to chew and shred the meat.

## Behaviour and sociality

Terrarcaulians are actually quite social, living in communal groups. Terrarmis lives in groups, foraging together in the woodlands, and serve an important role in their environment, such as spreading seeds and spores across the island, which get stuck in their feathers. Dergols live in herds where they use mutual protection for their never ending walks through the arid deserts and grasslands in search of sources of freshwater. Mud stalkers also live in groups, where they together hunt the abundance of aquatic fauna in the swamps. The groups that terrarcaulians largely do not show any hierarchy, just a demonstration of their preference in living in groups for mutual protection and general company.

## Reproduction

Terrarcaulians are oviparous. Despite being terrestrial, they lay their eggs on the water, where their young breath through feathered gills that are supported by atrophied remnants of the first pair of limbs, and only later they come out of the water to perform a life on land. They display different forms of sexual display. Terrarmis show off their white feathers, once part of their, now useless, respiratory gills, to attract a mate, and they may often color the feathers with ocre, blood and sap, to make them visually appealing. The mud stalker uses a large dorsal fin, a remnant of its aquatic larvae, to impress mates. Dergol show off sideways to the mate, showing its general bulk. Once they mate, the eggs are laid in a small stream of flowing water, covered in a protective slime to avoid them being eaten or attacked by predators. The mother will keep an eye on the eggs, and once they hatch, they will be laid eyes by the mother for a few months, when in an aquatic life. The terrarcaulian offspring have fins in their dorso that they use to swim around. Once they come out of the water and are ready to walk and run on their own, the mother will cease to take care of them and they will be ready to fend for themselves.