Numerous specimens belonging to an undescribed macrodasyid gastrotrich species were recovered during a survey of the biota associated with the severely dysoxic sediments of the Santa Barbara Basin, off California, U.S.A. Densities of this species reach 10 specimens cm−2.
Urodasys anorektoxys sp. nov. is described and figured. Specimens of this taxon attain the largest size within the genus; body, excluding the motile tail, is up to 1100 μm in length. Adults are protandric, then simultaneous hermaphrodites and lack a stylet-like sexual structure;
the main morphological traits include (1) a unitary ventral ciliary field, and (2) a pharyngeal region that bears a total of 14 pairs of adhesive tubes, 12 pairs ventrolaterally and two pairs dorsolaterally. The systematic position of the new species is discussed.
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