Megadontia

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

## Evolution and taxonomy

Megadontians are the most diverse group of spinodontians, a group of derived jawed crucissymbioticans. Spinodontians have originated in the Scelusian some 171 million years ago, and divided into two branches, one which later give rise to the predators with cartilaginous skeleton, known as concavotheres. The first concavotheres originated in the late Scelusian as well, 161 million years ago. The lineage that gave rise to the megadontians only really started to diversify in the aftermath of the Scelusian-Variagene extinction event. The first megadontians originated in the Variagene, 123 million years ago, and they differentiate themselves from the concavotheres, for having a bony vertebral column and ribs, a product of their ossified endoskeleton, and jaws made out of the central proboscis instead of being from the lateral ones. The megadontians are divided into several groups. Spinodon is tha basalmost and a sister taxon to the Meganepirria clade, which is characterized for having external bony armor on the belly, at some extent. Meganepirrians originated 94 million years ago in the Compsogene, having started to get adapted to the warmer ocean waters. The nepiirovermians are the biggest subclade of meganepirrians, characterized for having a much more defined jaw, made exclusively by the central proboscis and attached to the head, without requiring the support of a long rostrum. Nepirrovermians originated in the Compsogene, 65 million years ago. Nepirrovermians are then divided in two clades. The antefleakseaoideans originated in the Recensgene, 32 million years ago. These were initially marine predators, but the only survivors exist in freshwater courses. These are active predators, using large central proboscis armored jaws and the barbed lateral proboscis to restrian prey. The other nepirrovermian clade are the viridinepirrians, which include the nepirrs, and first evolved 35 million years ago in the Recensgene. These are large armored beasts, with dorsal and ventral armor, with fleshy jaws made out of the central proboscis and lateral proboscis used as feelers, to sense the surroundings.

Spinodontia (171-0)

* Concavotheria (161-0)
* Megadontia (123-0)
	+ Spinodon
	+ Meganepirria (94-0)
		- Megapterigia epifanus
		- Nepirrovermia (65-0)
			* Antefleakseaoidea (32-0)
				+ Antedsaaksee dragofleaksea
				+ Hunter scavenger worm
			* Viridinepirria (36-0)
				+ Green-tailed nepirr
				+ Nepirr

## Characteristics

Megadontians have various different derived features that makes them pretty unique. One of the most prominent characteristics is how they have their proboscis organized. The "jaws" are formed by the central proboscis in megadontians, but they are differently organized in each group. Spinodon is the basalmost and has an upper jaw composed of the rostrum, with the lower jaw being the central proboscis filled with tooth-like protrusions. The "upper jaw" also has "teeth" as a result, to make a formidable mouth. The lateral proboscis are usually retracted but they sometimes come out to direct the food into the mouth. They feed just through the central proboscis, which in the case of Spinodon, its located at the base of the central proboscis. The meganepirrians have a central proboscis branched into two vertical ends, each having its own set of teeth, though some later forms eventually lost these. Megapterigia has the lateral proboscis displayed out of the mouth, with several filamentous branches to catch microorganisms, which it then leads to the central mouth to feed on. One characteristic of the meganepirrians is that they largely have a reduced rostrum, which allowed them to better evolve the central proboscis jaw. Nepirrovermians have a defined central mouth attached to the head. As larval forms, they still have very reduced central proboscis, heavily relying on the lateral proboscis to catch food. Adults eventually use their central proboscis with much more frequency. Adult antefleakseaoideans have armored central proboscis jaws, filled with external serrations, as well as teeth. Their lateral proboscis are held inside the mouth but they often come out to restrain prey, using their sharp barbed ends. Viridinepirrians have a defined central proboscis mouth, with the lateral proboscis working as "feelers", long strings that detect the surroundings and nearby vibrations. The green-tailed nepirr retains teeth in its mouth, to catch and crunch prey, but common nepirrs are toothless and prefer soft polyspeculates and at best, soft eggs of other creatures. The eyes of most spinodontians are the typical compound eyes of the basal celernantids. Antedsaaksee though has evolved focalized lens in its eyes, though those are very primitive and are largely just for the sake of making the eyes look like those of the Osteosuchus gomphiobian, to which this creature is very simillar. The olfactory orifices are also positioned differently in megadontians. Spinodon has them in a much weirder position, being placed in elongated receptors, sort of like makeshift whiskers, to sense the smell of food around its environments. Meganepirrians tend to have the olfactory orifices in the tip of the head, just at the base of the proboscsi, or even migrating deeper into the upper jaw, to serve as a form of detecting food around. The respiratory orifices are also positioned differently. Basally megadontians have the respiratory orifices at the sides below the limbs, like the basal celernantid. However nepirrovermians have migrated their relevant respiratory orifices in a vertical row of orifices just behind the head, in the neck. Megadontians basally have eight limbs. Spinodon basally has typical small bony limbs, that serve little purpose in propulsion, and are just used for simple stabilization during swimming. Meganepirrians however start evolving large flippers. Megapterigia has huge muscular flippers, supported by a bony support. Viridinepirrians also have eight muscular flippers. Antefleakseaoideans, however, have simple flippers, supported by a bony support and somewhat articulated, and with bony armors, cartilaginous extensions or just skin, to help construct rudimentary flippers. Antefleakseaoideans are the only megadontians with less than eight limbs... they instead have six. Their method of locomotion is also variable. The basal Spinodon moves through its paddle-like tail fluke, which is oriented vertically like a fish. Meganepirrians have lost the tail fluke ans started moving with their flippers. Eventually some have regained usage of the tail for locomotion, such as the hunter scavenger worm, which has a very long tail, with a long eel like fluke. Viridinepirrians have re-evolved a tail fluke, but its horizontal, like those of cetaceans. The endoskeleton of megadontians distinguishes them from their concavothere relatives, having a bony endoskeleton, filled with a bony vertebral column, ribs and limbs. All megadontians have external armor, specially in the dorso, with varying extents and functions. Megapterigia has dorsal plates that are fed by some purple polyspeculates, which in turn release sugars to feed the large filter feeding creature. The bony armor of megadontians is filled with calcium and nitrogen, which makes them nutritious resources for parasites and even for other creatures that find their carcasses. The common nepirr, due to being toothless, uses an extension of the bony armor in its head to use as a tool to strip off floral material. Meganepirrians are a group that is mutually identified by the presence of ventral external bony armor, that protects them from predatory attacks from below.

Megadontians are highly variable in their size. The hunter scavenger worm is 1,5 meters long as a fully grown female. Antedsaaksee measures 4 meters long. The green-tailed nepirr is 6 meters long, while the common nepirr is 14 meters long. The largest is the filter feeding Megapterigia, with 15 meters in length.

## Distribution and habitat

Megadontians, despite their diversity, are not spread in the entirety of the planet. The basalmost Spinodon is the only found in the antarctic ocean waters of Virtu. Megapterigia epifanus is a filter feeder that prefers the secluded oceanic ecosystems that surround Occidentis. The green-tailed nepirr is also found around Occidentis, separated geographically from the common nepirr which lives in the shallow warm oceanic waters around Media Insula. The antefleakseaoideans exist in freshwater though, despite that they were once present in marine waters. Antedsaaksee is found in the large Musa Sapientum Fixa lake in Media Insula. The hunter scavenger worm is a freshwater hunter in the cold murky rivers and lakes of northern Occidentis.

## Diet

The diet of megadontians is variable. Spinodon is a carnivore, using its makeshift jaws with long thin sharp teeth to trap its prey. Megapterigia is a filter feeder, using its lateral proboscis filled with filamentous branches that trap microorganisms that are then brought to its central mouth. The skin in its flippers is also covered in small velvet-like rugosities that trap microorganisms, which the Megapterigia often uses as a secondary food catching method. Eventually it will use its proboscis to grab any microorganisms that might have been stuck in the flippers and are then directed to the mouth. This also attracts a myriad of small dispeculates that go to the Megapterigia's flippers to eat the small organisms that get stuck there. Its dorsal armor is rich in calcium and nitrogen, which is parasitized by polyspeculates, which in turn release sugars that feed the Megapterigia. Antedsaaksee is a carnivore hunting smaller prey than itself. It usually is not an active hunter preferring slower prey or carcasses, using its Osteosuchus like appearance to incite fear, so that it can have a free meal in any carcass. The hunter scavenger worm, has a unique form of killing prey. It is an ambush predator pursuing and imobilizing prey with its jaws and proboscis, only to constrict the prey with its long tail. The green-tailed nepirr is a carnivore, eating eggs and smaller fish-like creatures, using its teeth to crush the small prey. The common nepirr, however, is a large herbivore, feeding on polyspeculates, using its armored protuberance in its snout to strip the floral material it feeds on, in the lack of teeth. It sometimes, however, feeds on eggs of othe creatures.

## Behaviour and sociality

Megadontians are largely solitary, but some are often seen living in small groups of up to 10 individuals. Females are usually larger than the males. Their eyes are very sensitive and dependant of light, which they use to see their surroundings, though some species are slightly more adapted to life on murky waters, such as antefleakseaoideans, which granted them a free pass in living in freshwater.

## Reproduction

Megadontians produce eggs for reproduction. All megadontians have simple forms of sexual display, opening their mouths and showing their lateral proboscis, is a typical form of display for all megadontians. Once the female accepts them, the female will lay her eggs in shallow waters. The number of eggs in variable. For example, the common nepirr lays just one large egg. The number of eggs of other megadontians is also not very big, with up to 10 eggs being laid. The male will then externally fertilize the eggs, and the parents will then abandon the eggs to their fate. Megapterigia, due to being a largely pelagic creature, is impractical to go to shallow waters to lay her eggs, so the female instead developed a sack of eggs that are attached to the uterus. They come out so that the male can fertilize the eggs, and then the female will eventually place the sack right inside her. The babies will eventually hatch inside the mother's uterus, and then they are given birth, ready to live on their own. This is one of the few ovoviviparous strategies of reproduction known in extant celernantids.