Ophiolofsson Thuy & Eriksson & Kutscher & Numberger-Thuy 2024

Genus Ophiolofsson gen. nov. urn:lsid:zoobank.org:act: 8F0B9C56-6C24-4AB3-B752-55E3F7EAE41C Type species Ophiolofsson obituary gen. et sp. nov., by present designation. Diagnosis Ankhurid ophiuroid with thick, rounded lateral arm plates showing articulations for ambulacral groove spines, lacking a ventro-proximalwards protruding ventral portion, and having and a well-defined, strongly prominent vertebral articulation knob situated directly at the dorsal edge of the lateral arm plate; vertebrae roughly cylindrical; lateral sides with large, oval articulation surface proximally, matching vertebral articular knob on inner side of lateral arm plates; distal side with large, dorsally converging zygocondyles; water vessel canal running entirely within vertebra, distally enclosed by large zygosphene. Etymology Genus name honoring Swedish ‘metal painter’ Pär Olofsson in recognition of his artistic talent and ability to integrate complex anatomical features in remarkable scientific accuracy into his art pieces, making them disturbingly vivid. Gender: masculine. Other species included Ophiolofsson joelmciveri gen. et sp. nov., O. immolation gen. et sp. nov., O. archspire gen. et sp. nov., and O. hendersonorum gen. et sp. nov. Remarks Ophiolofsson gen. nov. and Ophiopetagno are the two basalmost representatives of the extant ophiuroid clade Ankhurida clade nov. currently known. They are also the only ankhurids with ambulacral groove spine articulations, resulting in a unique combination of ancestral and derived characters not found in any other known ophiuroid. Closest similarities are shared with the lateral arm plates of the basal zeugophiuroid genera Lapworthura Gregory, 1897 (Gladwell 2018) and Hallaster Stürtz, 1886 (Spencer 1925). The lateral arm plates of those two genera, however, lack tentacle notches, a ventro-distalwards protruding ventral portion and an outer surface ornamentation. In addition, their ambulacrals are, albeit opposing, not fused into vertebrae. Lateral arm plates of furcasterids, eospondylids and onychasterids all lack a tentacle notch and share a particular type of spine articulation strongly differing from the simple opening seen in the lateral arm plates of Ophiolofsson and Ophiopetagno. The latter two genera can thus be readily distinguished from all other currently known ophiuroids. The lateral arm plates of Ophiolofsson gen. nov. differ from those of Ophiopetagno in being thicker, having a much smaller ventro-distalwards protruding ventral portion and a strongly prominent vertebral articulation knob located directly at the dorsal edge, altogether leading to a lateral arm plate shape that appears less strongly wrapped around the vertebra. Since these differences are consistently found across various species, we consider them to be genus diagnostic.