Abstract: A new, very large species of Cladorhiza, collected from 1,442 m depth on the San Juan Seamount, S. California,
by the ROV ‘Tiburon’, is strikingly bilateral in symmetry and feather-like in form. The specimen, 382 mm in total length,
consists of a narrow stalk attached to hard substrate by a small disc, and an elongate spatulate body. The main body, triangular
in section, bears a continuous fringe of about 400, 21-mm-long marginal filaments and a series of 13 fleshy lobes projecting
from the midline of the frontal surface. Major biologic processes are regionally separated. Male reproduction (as spermatic
cysts) is restricted to the tissues of the frontal surface of the main body, including the frontal lobes. Female reproduction, as
oocyte production, embryo development and larval maturation, occurs exclusively in two abfrontal surface tissue bands in the
cushions between the keel and the more fleshy main body. Prey, exclusively small crustaceans, are captured and digested only
on/in marginal filaments. The elegant bilateral symmetry attained by this species attests to the continuing experimentation
with development patterns within Porifera.