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1 October 2012 A new deep-sea species of harrimaniid enteropneust (Hemichordata)
Nicholas D. Holland, Karen J. Osborn, Linda A. Kuhnz
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Ninety-two individuals of a deep-sea harrimaniid enteropneust were imaged between 1675 m and 3225 m off the California coast. Of these, about three-fourths were positioned with their posterior regions buried in sediment or hidden by rocks, and the rest were completely exposed on the substratum. When visible, the posterior end of each worm was typically associated with a dense tangle of fecal strands. One specimen was captured and is described here as the holotype of Saxipendium implicatum. In life, it was 22 cm long, and the color of its dome-shaped proboscis, narrow collar, and anterior trunk was medium orange. No wing-like folds of the body wall protruded anywhere along the length of the worm. The proboscis complex included a stomochord and glomeruli, but neither a heart nor a pericardial cavity could be detected. Most of the dorsal collar nerve runs along an open invagination in the dorsal midline of the collar and is only roofed over very briefly at the posterior extremity of the collar. Another unusual feature is the exaggerated posterior extension of the horns of the proboscis skeleton, which projected into the anterior extremity of the trunk. The trunk commenced anteriorly with a pharyngeal/esophageal region that included a tract of ovaries on either side of the dorsal midline. The ripest ovaries contained a single oocyte approximately 700 μm in diameter (presumably this species is gonochoric, although no males have yet been collected). The gill skeleton lacked synapticles. More posteriorly, the trunk housed a long, darkly pigmented hepatic intestine without sacculations and a short, lightly pigmented post-hepatic intestine. The geographic range of S. implicatum appears to be restricted to the Davidson, Guide, and Taney Seamounts region in the eastern Pacific offshore of Central California.

Nicholas D. Holland, Karen J. Osborn, and Linda A. Kuhnz "A new deep-sea species of harrimaniid enteropneust (Hemichordata)," Proceedings of the Biological Society of Washington 125(3), 228-240, (1 October 2012).
Published: 1 October 2012

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collar nerve cord
proboscis skeleton
seamount fauna
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