Orphnurgus Théel, 1879

Genus Orphnurgus Théel, 1879 View in CoL

Diagnosis. (following Thandar, 1992). “Tentacles 15–20, non-retractile, discs with ramified processes. Circumoral papillae absent. Spicules spatulated crosses and/or rods of greatly varying shape, either spatulate, spindle-shaped, smooth with dichotomous ramifications, or spinous, often a combination of two types.”

Remarks. Another charismatic deep-sea megafauna, with IOT samples typically elongated and pink or orange (in life) with prominent papillae and tube feet. The conspicuous dorsal papillae are likely used for respiration ( Rowe et al., 2017). Of the nine species known worldwide for this genus, only two have been previously recorded for Australia: Orphnurgus glaber from off the north-west coast, and O. insignis from off the eastern coast, from New South Wales and the Lord Howe Plateau in the Tasman Sea (WoRMS and ALA, 2024). Thirtysix lots of Orphnurgus were recorded from the IOT voyages at depths of 1019–2435 m, with lots further identified to OTU species level as follows: O. glaber (13 lots), O. insignis (17 lots), Orphnurgus sp. MoV. 7318 (5 lots), and Orphnurgus sp. MoV. 7332 (1 lot). Distinguished from Deima by unretractable tentacles, absence of circumoral papillae, and a typically elongate (rather than oval) body. Distinguished externally from Oneirophanta by tentacle disc margins (which are ramified/ branching in Orphnurgus but only knobbed in Oneirophanta ) but more easily by ossicles, which are transformed rods in Orphnurgus compared to perforated plates in most Oneirophanta . Orphnurgus glaber is potentially a species complex ( Rowe et al., 2017). The sequenced Orphnurgus from the IOT form three well-supported lineages (fig. S5). For both the COI and 16S genealogies, O. glaber and Orphnurgus sp. MoV. 7318 are sister lineages.