Phyllostoma

Phyllostoma (meaning 'leaf mouth') is the clade containing all multicellular organisms with a radial symmetry body found on the alien planet.

Phyllostome evolves from Bulbozoa whose bodies are more rounded and heavyweight, causing them to sink and roll around the seafloor. Eventually, the ancestral phyllostomes settle on the seafloor and become sessile.

Over millions of years, those that live in the shallow water slowly form a symbiotic bond with the phototrophic microbes, evolve to coexist with one another, and eventually become one being, known as the polyphyllophytes.

Anatomy
Phyllostomes have a round, bulbous body filled with mesohyl. They are noticeably larger than their ancestors and their bodies have radial symmetry throughout their live. Matured phyllostomes are sessile while their larvae are capable of limited mobility in the water.

Nervous System and Senses
Similar to their ancestors, their bodies are innervated with a decentralized nerve net, though highly concentrated at the appendages to increase their sensitivity.

Sticking Pad
In the ancestral stage, when they are still rolling on the seafloor, phyllostomes developed a specialized pad on the now bottom side of the creature to hold themselves down against hard terrain and prevent being carried away by water current, which makes this group able to survive and proliferate. Further evolution changes the role of this, however, as the adults are sessile while the juveniles become the one that selects the spot to settle instead.

Appendage Ring
On the "top" part of their body are six flat appendages covered in choanocytes, which act as extension of themselves. The appendages' main purpose is for feeding, by reaching out into the water and catches planktons. It also doubles as extension to absorb oxygen more easily as they have become sessile.

Sexual Reproduction
Around the same time that they developed the appendage ring, a sexual organ is also developed, located in the middle of the appendage ring. A phyllostome can produce both kinds of gamete. This trait makes phyllostomes become even more abundant and successful creature on the planet.

Larvae
Phyllostomes' larvae are very small, as big as their ancestors' mature size. Due to their size, the larvae can stay afloat in the water, carried around by the water currents. The time from spawning to larval settlement is around a month, after which the larvae settle on the seafloor, metamorphose, and develop the shells and reproductive organs. The feeding appendages develop very early after the fertilization and are capable of beating, granting them some degree of movement.

Behavior
Phyllostomes possess more advanced behaviors such as an ability to move their appendages around to increase the chance of catching planktons.

Reproduction
Due to them being a sessile creature, phyllostomes are unable to actively seek a mate. They, however, use a strategy called "broadcast spawning". Every full moon, enormous amounts of gametes are released into the water. Only a small amount of eggs and sperms met and fertilized. The adult also retain an ability to reproduce asexually, but through budding instead of binary fission.

Niche
Phyllostomes are filter feeders, feeding on planktons floating by or the marine snow. Their appendages are covered in choanocytes, which are used to filter food particles from the water. Their competitors are other phyllostomes and hexapterids nearby, which took the same niche. Sometimes, the eggs fall prey to hexapterids, and sometimes other phyllostomes. Those that live deeper face a problem of scarce food sources, which is only the marine snow falling from above.

After the emergence of gnathopterids around 4.25 billion years, they become secondary prey for both the adults and the juveniles alike. Due to this pressure from the new species, some species slowly develop hard shells made of calcium with a space for appendages, which have become thinner, to retract inside to increase the chance of surviving while still retain the same lifestyle. These groups eventually become cryptophyllostomes.

Distribution and Habitats
Phyllostomes live on the seafloor, from the shallow water to a depth of two kilometers. They can also be found nearly throughout the ocean. The only exception is near both poles, where the water is colder than the tropic zone.