sea pen

9.8

A marine animal like a feather made of many tiny animals on the sea floor

noun
/siː pɛn/

Specialized

: pluma de mar

So we found things like deep sea sea pens and corals that I had never encountered before from extreme depth.

Examples

A sea pen can be identified by its featherlike structure which extends from the ocean floor.
Along the sandy ocean bed, many sea pens swayed gracefully with the current.
The diver discovered a vibrant colony of sea pens nestled within the coral reef.

Synonyms

Pennatula

vssea pen

Specialized

9.9

A group of sea animals called sea pens that live together

is the common name for those colonial featherlike animals rather than a specific genus

sea feather

vssea pen

9.9

A coral that grows in feathery groups on warm ocean reefs

is a colonial animal with a soft featherlike body not a coral type

Surface Forms

sea pen singular

sea pens plural

Morphology

sea + pen

Although 'sea' is transparent, the constituent 'pen' is ambiguous (commonly understood as a writing instrument or an enclosure) and does not cue a marine colonial animal; the compound's zoological meaning comes from an extended/historical sense of 'pen' (like a quill/feather) that a B1 learner is unlikely to know. Because the meaning ('a featherlike marine animal') cannot be reliably derived from the ordinary senses of 'sea' + 'pen', this expression is opaque to learners.

Etymology

Sea pen gets its name because this soft, featherlike animal looks like a feather quill or old writing pen fixed to the sea floor. So the picture of a 'pen' standing in the sand helps you remember that it is a group of tiny animals anchored to the bottom.