Identification of an Unknown Marine Animal

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This is a daunting task as marine diversity is much greater than on land or freshwater. The reason for this predominance of marine higher taxa is believed to be because most of the fundamental patterns of organisation and body plan, i.e. the different basic kinds of organism that are distinguished as phyla, originated in the sea and remain there, but only a subset of them has spread to the land and into freshwaters.

To go about this problem it is helpful to have some background information on the typical phyla you may encounter upon dredging the seafloor.

"Characteristics of Different Phyla"

Porifera
These animals are asymmetrical, meaning they have no symmetry. They are filter feeders by means of flagellated cells. Filter feeders pump in water so that they can obtain their food from what is in the water. In some cases, the exit door or osculum can been seen with the naked eye. Example: sponges.

Cnidaria
Cnidarians have medusa and polyp cycles. The medusa cycle is free swimming such as a jellyfish. The polyp cycle is stationary such as an anemone. They have radial symmetry with stinging cells called nematocysts. Examples: Jellyfish, hydroid, anemones and coral.

Platyhelminthes
There are unsegmented worms that are flattened dorsoventrally. They move by contracting muscles down its body (ungulates). They have bilateral symmetry with two eyespots, that are sometimes visible. Example: Flat worms such as the Mexican skirt dancer.

Annelida
They are segmented worms with bilateral symmetry. Each of their segments have a pair of parapodia for movement, which are ususlly visible to the naked eye. Examples: Fire worms and tube worms.

Arthropoda
These animals have bilateral symmetry and segmented bodies. ...