Cetathalassa

**Cetathalassans** are a clade of ambulospeculids that are alive today.

## Evolution and taxonomy

Cetathalassans are a major clade of ambulospeculids, specially because they are the most relevant and successful aquatic clade descended from these, ancestrally, terrestrial creatures. They are part of the basalmost split of ambulospeculids, the epestridutchiians, which originated 259 million years ago in the late Tenerian. Cetathalassans are a sister clade to the terrestrial maiadorsans, both having originated and diversified with the aftermath of the Tenerian-Accomodatian extinction event, namely due to the violent climatic changes that caused the extinction of several species, and allowed these clades to take on the vacant niches. The first cetathalassans, originated in the Accomodatian, 220 million years ago, and were already aquatic, though they would stick to bodies of shallow waters, and go on land or shallow water to lay their eggs, where they would be safe. Eventually one major clade, the cetestians, has arrived and started to become more oriented to the open oceans, in the Scelusian, 181 million years ago. It was only with the Scelusian-Variagene extinction event, that they properly diversified to how they are today. One cetestian lineage, the cetestarexians, evolved 142 million years ago, in the early Variagene, and have become completely independent of going on land, and live a life in the open ocean. Their reproduction tactics have shifted, with some species becoming viviparous, while others guarded their eggs in their body, instead of laying them in the open ocean. The other cetestian lineage, include the triapsarians, which originated 136 million years ago, in the Variagene, including a wide variety of aquatic creatures. Ventuscibumians originated in the Compsogene, 96 million years ago, and are a clade of triapsarians that started to evolve "jaws", though these jaws were organized in different ways. Eventually the most derived clade of ventuscibumians are the thoravenatans, which originated in the early Recensgene, as oceanic faunal turnovers occured. These are characterized for having a lower jaw supported by head plating that is moved by muscles of their first pair of limbs.

Due to the basality of cetathalassans anatomy and morphology, early scientists believed they were part of the even more basal clade, the gomphiobians. However, genetic analysis recovered them as a basal ambulospeculid clade.

Epestredutchiia (259-0)

* Cetathalassa (220-0)
	+ Epestrepseapotithalassa
	+ Cetestia (181-0)
		- Cetestarexia (142-0)
			* Cetesta
			* Maretenuem rex
		- Triapsaria (136-0)
			* Triacrinasus dutchii
			* Ventuscibumia (91-0)
				+ Ventuscibum
				+ Thoravenata (46-0)
					- Spinobrachi velocivenatus
					- Thorakismenikefali psaria
* Maiadorsa (222-0)

## Characteristics

Cetathalassans have evolved various unique adaptations for the survival underwater, allied to the already existing adaptations as an ambulospeculid. Starting with their mouth apparatus, which have taken plenty of forms, but in ways that can be confidently traced back with their evolutionary proccess. The proboscis of the cetathalassans have been repurposed for various purposes, but basally, they all served a respiratory/feeding function. The proboscis of ambulospeculids, in general, have a simple respiratory function, that is more or less advanced in cetathalassans, which allow them to snorkel for air, instead of having to position their lateral orifices for breathing, although they did not loose breathing potential in those orifices at all. Basal cetathalassans use all proboscis for feeding. Epestrepseapotithalassa uses the three proboscis to feed and grab food in the forests it inhabits. Some species of cetestans have evolve a complex respiratory-digestive system, that connects the breathing mechanisms and the digestive system, to allow for a complex channel of air and food flux from the proboscis, to the respiratory orifices and to the anus. The largest cetestans are filter feeders, using the three large proboscis as huge tubes for the filtering of food, but others are predators, using the central proboscis, that has a hook for puncturing prey, and others, being more basal, lack the complicated respiratory-digestive system and use all three proboscis, filled with electromagnetic sensitive spikes, to detect the surroundings and grab and immobilize prey. Triapsarians have repurposed the usage of the lateral proboscis, being incapable of consuming food, leaving that task for the central proboscis. Each proboscis of the Triacrinasus has a three-tipped beak, that it uses to lacerate the food, while they also breath atmospherical air. Ventuscibum, however, has shrinked and internalized its lateral proboscis inside the skull and joined them to a pair of olfactory orifices (which are also repurposed for breathing air), while the central proboscis is instead stiffened and is used as a powerful and muscular "lower jaw". The thoravenatans have evolved another strategy for the making of jaws. The head plate that existed in their ancestors has split and joined the muscles of the first pair of legs, allowing for the required musculature to move this piece of head plate has a jaw. Spinobrachi has fully articulated arms that become deattached from the body and grow longer as it matures, drawing the head plate at the tip, forming a pair of lower jaws. Thorakismenikefali has, however, shrinked its frontal pair of limbs, to the point of vestigiality, though the muscles remain fully active to power the armored lower jaw. The proboscis of Spinobrachi have small teeth to grab prey, but its ultimately the central proboscis the one that feeds the creature. Thorakismenikefali has two long proboscis that come out of the mouth and grab the prey, while the central proboscis, with limited extendable potential, stays in the mouth, swallowing the food whole. The olfactory orifices of cetathalassans are a great example of repurposing those organs for other functions. Triacrinasus, for example, has evolved mucuous extensions behind the head that work as "olfactory gills", to sense the presence of their food. Beyond sensing smell, they have also been repurposed for breathing atmospherical air, as well as having developed them as hearing organs. Other dispeculates have managed to repurpose those for those tasks too, but cetathalassans are a clear example on the way they do it. Hearing orifices have evolved a specialized membrane, attached to a oil bladder, that vibrates and detects sounds. This technique is already used by various other dispeculates, in a more rudimentary form, by using a simple membrane behind the skull. The eyes of the cetathalassans are compound eyes, some having evolved focalized lens, specially in the case of triapsarians, whose lenses are squeezed within each individual eye in the compound eye, to better focalize the image. The eyes of the cetathalassans are very good at distinguishing different wavelengths of light, having four different types of photorreceptors, though some species of cetestans have evolved three additional new types of photorreceptors. The position of the respiratory orifices is variable. Basally, like the first ambulospeculids, the respiratory orifices were organized in horizontal rows under the arms. This characteristic be observed in Epestrepseapotithalassa and Triacrinasus, which proved complicated, as they would either have to position themselves to breath outside of the water, or use their probocis to breath. Eventually, many groups started to position their orifices above their limbs. Cetestans have orifices positioned at the sides or at the top of their bodies. Maretenuem and Ventuscibum have their orifices placed at the sides of the body, while the external armor prevents them from going to the top of the body. Thoravenatans have their orifices positioned at the very top of the body, sometimes sneaking between cracks on their dorsal armor. Cetathalassans, basally, have eight limbs, and they have repurposed them in varied ways across their evolution. Epestrepseapotithalassa screams as one of the weirdest cetathalassans, not only for the fact it was pressured to return to land. It is part of a long lost lineage that used their huge frontal limbs for locomotion, while the three pairs of limbs fused at the end of the body. Currently the frontal limbs are used as large bony scythes to help it climb trees and hills, as well as scythe the food it eats. The six fused limbs are atrophied and are only manifested by a bug spur at the end of the body. It moves around by slithering like a snake, thanks to its belly muscles and has developed external bony rugosities to help it move around. Cetestans have eight limbs. The basalmost cetestan uses its first pair of limbs as fins to help control its movement, while its six back limbs are atrophied and only manifest as small spurs. More derived cetestans have the two middle pairs working as main large fins, while the first pair is atrophied, having no function or at least are used for cleaning their eyes. The last pair of limbs is also atrophied, but are used as mating claspers. Maretenuem rex uses the last six limbs as fins, while the frontal pair is used to latch on and catch prey, stabbing them repeatedly. Triacrinasus has lost two of its limbs, presumably, the second and fourth pair of limbs, moving along just with their front and third pair, as large fins. Ventuscibum has eight limbs, its frontal pair is amored and wide to help with steering, but the three last pairs are thin and flat fins that move methodically for a unique method of underwater locomotion. Spinobrachi has eight limbs too, the first pair being used as jaws, the second pair being huge flippers that also help in moving on land, dig their nests and even attract mates, while the third and fourth pair are smaller and serve a secondary role for underwater locomotion and stabilization. Thorakismenikefali has lost the fourth pair of limbs, and the first pair is vestigial, with still functioning muscles powering the lower jaw of the creature, while the second and third pair are used as fins for locomotion, having a long spur to support a membrane that helps in underwater locomotion. The presence of external armor in cetathalassans is largely universal, but some members eventually lost these or atrophied them, such as streamlined predatory cetestans and Triacrinasus. Triacrinasus has an interesting integumentary feature however, which is characterized by the presence of small poisonous spurs on the sides of the body, which prevent them from being vulnerable to predatory attacks. Derived cetestan species have evolved a large orb in front of their head, which can create complex colors, that are used for display and, in some species, attract and hypnotize prey. Their method of locomotion is variable. Epestrepseapotithalassa is well known for moving like a snake on land. Cetestans have a horizontal tail fluke, often supported by cartilage rays or by a piece of flattened external armor. Maretenuem moves with a vertical tail fluke, just like many other cetathalassans like Triacrinaus, Spinobrachi and Thorakismenikefali. Ventuscibum move, methodically, with their last three pairs of limbs, to move underwater. Cetathalassans, unlike many other ambulospeculids, possess a cartilaginous skeleton. Their limbs, the complex endoskeleton and even the skull, is cartilaginous. The only ossified parts of the cetathalassans are usually in the exterior of the body. This seems to have been an adaptation from the semi-ossified nature of the first ambulospeculid's endoskeleton. Eventually a cartilaginous endoskeleton helped the cetathalassans to become lighter and more flexible in underwater locomotion.

The size of cetathalassans is highly variable, but many huge species exist, some of them are among the largest of all ambulospeculids. Maretenuem rex is one of the smallest, usually measuring 1,33 to 1,66 meters in length. The terrestrial Epestrepseapotithalassa measures 2,6 meters in length. The Ventuscibum has various species that range from 3 to 7 meters in length. Triacrinasus dutchii has a length of 10,5 meters. Thorakismenikefali is a behemoth apex predator of the oceans, measuring 15 meters long as males, and 17,5 meters long as females. The wide Cetesta clade has creatures of various sizes, ranging from a modest 2,4 meters in length, to a breathtaking 23,5 meters in length.

## Distribution and habitat

Cetathalassans, being one of the most influential aquatic clades of all, in Wallace II, are spread all across the globe, in almost every corner that has deep enough water, for them to swim on. There is only one species of fully terrestrial cetathalassan, the Epestrepseapotithalassa, whose ancestors were aquatic, but returned back onto land. Currently they exist in the cold and temperate swamps and forests of Virtu, where they live in perfect isolation. Cetestans, despite being a diverse group, are more localized in their geographical position, being found in the oceanic waters surrounding Occidentis. The related Maretenuem rex is found in the shallow waters of Vadum Mare. Triacrinasus dutchii lives in the cold oceanic waters that surround Terra Septentrionis. Ventuscibum is a varied clade that is spread across the oceans and freshwater courses of the entire globe. Spinobrachi is an exclusively freshwater creature, crawling onto land to lay eggs, and lives in the freshwater courses of Media Insula. Thorakismenikefali is a fully marine predator, that is spread all across the globe.

## Diet

The diet of cetathalassans is varible, ranging from herbivory, to omnivory and to carnivory. Epestrepseapotithalassa is a terrestrial omnivore, feeding on dispeculate and polyspeculate matter in the forest floor, using their long frontal limbs to scythe the food it needs. Cetesta are varied in their diet. Basally they are predators, hunting prey through chasing or through ambush, though the largest species are gigantic filter feeders. Some predatory cetestans, more closely related to the filter feeding kind, use their color changing orb to hypnotize prey. Maretenuem rex is a predator using its frontal limbs to stab prey repeatedly until it consumes it. Triacrinasus dutchii is a herbivore, feeding on polyspeculates. Ventuscibum is a varied clade, with omnivorous, herbivorous and carnivorous species. Spinobrachi and Thorakismenikefali are exclusively predatory, hunting their prey ferociously with their weird jaws.

## Behaviour, sociality and intelligence

Cetathalassans display varying degrees of behaviour and sociality. One interesting common characterstic is the echolocation abbilities, which has evolved in many species of this clade, with Thorakismenikefali being a pretty notable example, in how it is used with more efficiency. Sociality is also differently achieved in the different species. Epestrepseapotithalassa is solitary, except in the mating season where they seek each other. Cetestans may live in hunting packs, hunt solitarily or live in family groups, the latter in the case of the filter feeding species. Maretenuem rex tend to travel in small groups, though they don't have to necessarily be connected through mating bonds, but they do, sometimes, hunt prey together. Triapsarians, as a whole, like to live in groups, often formed by a couple of mating pairs. They may join together in large numbers during the mating season, or not, and be friendly or hostile to other groups whenever they join each other, ultimately will depend on the species. Cetathalassans are known for having a good degree of intelligence, with species existing that exhibit coordination in group hunting, and some, like the highly intelligent Thorakismenikefali, have been observed playing with objects, displaying this behaviour since young. Thorakismenikefali's intelligence has been comparable to that of the dolphins, making these one of the most intelligent creatures in Wallace II.

## Reproduction

Cetathalassans reproduce through internal fertilization. Basally, cetathalassans are oviparous, laying eggs. However these eggs can't just be laid in the open in the water. They either require protection or they require being laid on land. Many species eventually evolved various strategies to deal with that issue, one of them was abandon egg-laying altogether and become viviparous. Viviparity has evolved four times independently in cetathalassans, as a growing necessity of becoming fully dedicated to their aquatic lifestyle. Epestrepseapotithalassa lay their eggs on land, likely a strategy that forced these creatures to return back on land as a whole, as the complicated task of having to crawl onto land to lay their eggs was complicated to maintain. They still require to lay their eggs in moist places, as they are basal ambulospeculids, and their eggs still require moisture to develop. When the babies hatch, they hatch out as larval-like creatures, however, able to breath atmospherical air just fine, and will eventually change as the ontogeny occurs. Cetestans are unique among cetathalassans for having become totally aquatic, yet not abandoning their oviparity. They attract their mates using their color-changing orbs, and in the species that lack these, they use their colorful dorsal fins for display. The male will eventually position itself to mate with the female. Its cloaca has a penile-like growth that receives the females eggs, which are then fertilized by the male. These eggs stay attached close to the cloaca, often covered in a mucus that is used to protect the eggs from predators. The male will eventually go to shallow waters (in the case of social species, the male will abandon the group, normally just temporarily) and the eggs will hatch out several larvae, which the male will eventually abandon to their fate. The babies require going to the surface to breath when they hatch out. The related Maretenuem instead developed viviparity. The male fertilizes the female and she will gestate her offspring for three months. They will eventually be born tail first so to not drown. The offspring are larval-like and will swim to the surface to breath and live their lives without their mother. In the case of triapsarians, the game changes, as young are more developed when they are born, and will stick with their parents for a short amount of time and abandon their parents protection way before reaching maturity. Triacrinasus tends to open its beaked proboscis to engage in combat with males, but the combats are usually not very violent. The females will eventually be fertilized internally, and give birth to the young. Triacrinasus has evolved viviparity independently, a feature also present in Ventuscibum, which also evolved viviparity independently. Ventuscibum live in small groups, but gather in larger numbers for the mating season, where males open their mouths and ram against each other, but usually not in a too violent fashion. The female will gestate the offspring. Ventuscibum has a high reproductive rate. Spinobrachi is oviparous. Its phylogenetic position dictates how cetathalassans evolved viviparity independently over the course of the last millions of years. Spinobrachi still retain abbilities of crawling onto land, like a sea turtle. They gather in large groups, where the males display their bright red knobs. After mating the females will dig a hole on the sand where the eggs will be laid. The moist sand allows them to be protected. She will eventually take a good look at the nest, to see if it is not being raided. The babies will eventually hatch out of the nest, and the mother will protect them for a while, before they reach a considerable size. Thorakismenikefali is a relative of Spinobrachi, but one that evolved viviparity independently, yet again. This creature mates for life and creates long lasting mating bonds. The male turns upside down to mate with the much larger female, a characteristic common in many cetathalassans, in which the female is the largest sex and is the one that is not submissive during the mating. The female will eventually carry the babies in her womb, until the live birth occurs. The babies will stay in the group for a while, until they reach a considerable age that allows them to live on their own, and when they reach maturity, they can then proceed to find a new group.