Ophiopetagno kansas, Thuy & Eriksson & Kutscher & Numberger-Thuy, 2024

Thuy, Ben, Eriksson, Mats E., Kutscher, Manfred & Numberger-Thuy, Lea D., 2024, The beginning of a success story: basalmost members of the extant ophiuroid clade from the Silurian of Gotland, Sweden, European Journal of Taxonomy 947 (1), pp. 216-247 : 235-237

Ophiopetagno kansas sp. nov.

urn:lsid:zoobank.org:act:50FC1EAE-EDFA-4383-B0CF-40A185EA421F

Figs 5E–J , 7

Diagnosis

Species of Ophiopetagno with lateral arm plates of oval general outline, with a clearly convex dorsal edge, a fine outer surface tuberculation, and three small, weakly prominent lateral spine articulations in a continuous row.

Etymology

Species named after American rock band Kansas, for producing some of the most inspiring songs in the history of rock music, including ‘Carry On Wayward Son’ and ‘Dust in the Wind’.

Type material

Holotype

SWEDEN • Gotland, Tjälderviken ; NRM PAL Ec38338 .

Paratypes

SWEDEN • 2 specs; same data as for holotype; NRM PAL Ec38339 , NRM PAL Ec38340 .

Type locality and stratum

Wenlock Series, Whitwell Stage, Ozarkodina sagitta sagitta conodont Zone, Slite Group (upper part – “ Pentamerus gothlandicus beds” or equivalents); Tjälderviken, Gotland, Sweden.

Description

Holotype ( Fig. 5E–F )

NRM PAL Ec38338 is a dissociated proximal lateral arm plate nearly two times as long as high, relatively thin, with weakly convex dorsal edge, strongly convex distal edge and angular concave proximal edge, lined by pinnacled band of more finely-meshed stereom followed by elevated band of more coarselymeshed stereom showing weak horizontal striation; ventral portion long, weakly protruding ventro-proximalwards, with evenly convex ventral edge with five weak protrusions for ambulacral groove spine articulations and small, moderately deep tentacle notch incision; outer surface with fine tuberculation covering entire outer surface except for double band along proximal edge; three relatively small, prominent, freestanding lateral spine articulations composed of round opening surrounded by elevated, irregular ring, roughly equal-sized, arranged in continuous row along entire distal plate edge, distally bordered by very broad, low and relatively thin shelf. Inner side of lateral arm plate ( Fig. 5F ) with large, rounded triangular, well-defined and prominent vertebral articular surface at some distance from inner dorso-proximal corner and separated from inwards-protruding dorsal edge; tentacle notch relatively wide, deep, moderately well-defined, with incision in ventral edge; five to six small ambulacral groove spine articulations along entire ventral edge.

Paratype (supplements)

NRM PAL Ec38339 ( Fig. 5G–H ) is a dissociated median lateral arm plate approximately 2.1 times as long as high, similar to holotype but devoid of clearly discernible ambulacral groove spine protrusions along ventral edge; three lateral spine articulations similar to those of holotype but smaller. Vertebral articular ridge on inner side longer and in more ventral position than that of holotype; ambulacral groove spine articulations not clearly discernible.

NRM PAL Ec38340 ( Fig. 5I–J ) is a dissociated distal lateral arm plate almost three times as long as high, with straight dorsal and ventral edges; no ambulacral groove spine articulations discernible along ventral edge; three spine articulations as in holotype. Vertebral articular ridge on inner side longer and more prominent than that of holotype; tentacle notch deeper and more sharply defined.

Remarks

Among the species of Ophiopetagno that have a fine outer surface tuberculation of the lateral arm plates, Ophiopetagno kansas sp. nov. stands out in having lateral arm plates with an overall oval outline with a clearly convex dorsal edge, and much smaller and less conspicuous lateral spine articulations.

Occurrence

Tjälderviken.

Figures

Fig. 5. Dissociated lateral arm plates of ophiuroids from the Silurian of Gotland. A–B. Ophiopetagno bonzo sp. nov, holotype, NRM PAL Ec38336, proximal lateral arm plate in external (A) and internal (B) views. C–D. O. bonzo, paratype, NRM PAL Ec38337, median to distal lateral arm plate in external (C) and internal (D) views. E–F. Ophiopetagno kansas sp. nov, holotype, NRM PAL Ec38338, proximal lateral arm plate in external (E) and internal (F) views. G–H. O. kansas, paratype, NRM PAL Ec38339, median lateral arm plate in external (G) and internal (H) views. I–J. O. kansas, paratype, NRM PAL Ec38340, distal lateral arm plate in external (I) and internal (J) views.K–L. Ophiopetagno paicei Thuy, Eriksson & Numberger-Thuy, 2022, from Thuy et al. (2022), proximal lateral arm plate in external (K) and internal (L) views. M–N. O. paicei, from Thuy et al. (2022), distal lateral arm plate in external (M) and internal (N) views. Abbreviations: AGSA = ambulacral groove spine articulations; di = distal; do = dorsal; LSA = lateral spine articulations; TN = tentacle notch; VAK = vertebral articular knob.

Fig. 7. Stratigraphic position of the taxa described in the present paper with their assumed evolutionary relationships and the nesting of the clades Ankhurida clade nov., Ophiovalida clade nov. and Metophiurida Matsumoto, 1913. Note that some lateral arm plates are mirrored to allow comparison in similar orientation.