Two new species of Hyalonema (Hexactinellida, Amphidiscosida, Hyalonematidae) from the Indo-West Pacific.

This study describes two new species collected from deep-sea environments in the Indo-West Pacific. Hyalonema (Cyliconema) dexiangisp. nov., collected from the Indian Ocean, is characterized by distinctive finger-like protuberances on the body surface, the presence of choanosomal pentactins, the co-occurrence of micropentactins and microhexactins, and the absence of mesamphidiscs. Hyalonema (Cyliconema) subconicasp. nov., sampled from a seamount in the western Pacific Ocean, is distinguished by the presence of pinular diactins, a unique combination of choanosomal spicules (diactins, pentactins, and hexactins), and the presence of basalia bearing two-toothed anchors. In addition to their morphological distinctions, molecular phylogenetic analyses based on 16S rDNA sequences indicate a close genetic relationship between the two species.