The attachment of a small edrioasteroid to the nonperiproctal surface of a small specimen of the pleurocystitid rhombiferan Amecystis has implications for the life posture of pleurocystitids and indicates that Amecystis was epifaunal. Articulation of the preserved portions of both thecae indicates that the edrioasteroid and Amecystis were alive at or very near the time of burial and that the edrioasteroid used the Amecystis theca as an attachment surface. Other examples of edrioasteroids attaching to live organisms are known suggesting that an edrioasteroid attached to a live rhombiferan is not highly unusual. The position of the edrioasteroid on the rhombiferan suggests that Amecystis was oriented with the anal side down in life and that this pleurocystitid was fully epifaunal.

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