What is "xenophyophore"

n. A giant unicellular organism found in deep parts of the ocean.

Xenophyophores are giant multinucleate single celled organisms found on the ocean floor throughout the world's oceans, at depths of 500 to 10,600 meters (6.6 miles). They are a kind of foraminifera that extract minerals from their surroundings and use them to form an exoskeleton known as a test.

They were first described by Henry Bowman Brady in 1883. They are abundant on abyssal plains, and in some regions are the dominant species. Fourteen genera and approximately 60 species have been described, varying widely in size. The largest, Syringammina fragilissima, is among the largest known coenocytes, reaching up to 20 centimeters in diameter.