A number of soft fragments of uncertain identity, mostly taking a form of a disk or button, were found among trawled material from the hadal zone (7426–7654 m in depth) in the Japan Trench during the cruise KH-22-8 of the R/V Hakuho-maru in October 2022. These enigmatic ‘disks’ subsequently turned out to be the proboscides of enteropneusts severed from the collar. A molecular phylogenetic analysis based on the mitochondrial 16S rRNA and nuclear 18S rRNA gene sequences determined from one of the fragments along with others available in public databases indicated that the species in question was sister to the harrimaniid enteropneust Stereobalanus canadensis (Spengel, 1893). Some morphological features of the fragments—the proboscis longitudinal musculature arranged in radial plates, the four tubular ovaries, and the absence of synapticula on the gill bars—support that the Japan Trench species would belong to Stereobalanus Spengel, 1902. This study represents the deepest record of Stereobalanus and the first report of enteropneusts from the Japan Trench hadal zone, albeit identified to the genus level. While the species is putatively undescribed, a formal taxonomic description should await intact specimens in future studies.

在日本海沟 KH-22-8 号巡航期间，在日本海沟深渊带（深度 7426-7654 米）的拖网物质中发现了一些身份不明的软碎片，大多呈圆盘或纽扣状。R/V Hakuho-maru，摄于 2022 年 10 月。这些神秘的“圆盘”随后被证明是从项圈上切下的肠肺蠕虫的长鼻。根据从其中一个片段以及公共数据库中提供的其他片段确定的线粒体 16S rRNA 和核 18S rRNA 基因序列进行的分子系统发育分析表明，所讨论的物种是 Harrimaniid Enteropneust Stereobalanus canadensis 的姐妹（斯彭格尔，1893）。碎片的一些形态特征——长鼻纵向肌肉组织呈放射状排列、四个管状卵巢以及鳃条上没有突触——支持日本海沟物种属于 Stereobalanus Spengel，1902 年。这项研究代表了最深的研究立体巴拉努斯的记录和来自日本海沟深渊带的肠菌的首次报告，尽管已鉴定为属水平。虽然该物种被认为尚未被描述，但正式的分类学描述应该等待未来研究中完整的标本。