Ophiopetagno bonzo, 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 : 233-234

Ophiopetagno bonzo sp. nov.

urn:lsid:zoobank.org:act:7831EF97-5222-4624-81A5-7DD3AD1FC89D

Figs 5A–D , 7

Diagnosis

Species of Ophiopetagno with lateral arm plates showing a weakly convex dorsal edge, a conspicuous, coarse outer surface ornamentation, an oblique distal edge, three relatively small, inconspicuous lateral spine articulations, up to seven small ambulacral groove spine articulations along the entire ventral edge in proximal plates, indiscernible in median to distal plates.

Etymology

Species named after John H. Bonham (RIP), also known as ‘Bonzo’, former drummer of rock band Led Zeppelin, for raising drumming in rock music to a new level.

Type material

Holotype

SWEDEN • Gotland, Nyhamn ; NRM PAL Ec38336 .

Paratype

SWEDEN • 1 spec.; same data as for holotype; NRM PAL Ec38337 .

Type locality and stratum

Llandovery Series, Telychian Stage, Pterospathodus amorphognathoides conodont Zone, Lower Visby Formation (units a and b); Nyhamn, Gotland, Sweden.

Description

Holotype ( Fig. 5A–B )

NRM PAL Ec38336 is a dissociated proximal lateral arm plate nearly two times as long as high, relatively thin, with weakly concave dorsal edge, oblique, convex distal edge and irregularly concave proximal edge, pinnacled and lined by narrow band of more finely meshed stereom; ventral portion very long, weakly protruding ventro-proximalwards, with evenly convex ventral edge with seven weak protrusions for ambulacral groove spine articulations and small, shallow tentacle notch incision; outer surface with conspicuous, coarse tuberculation consisting of trabecular intersections transformed into irregularly-sized, prominent knobs, covering entire outer surface except for narrow band along proximal edge and stereom distally bordering spine articulations; four relatively small, inconspicuous lateral spine articulations composed of round opening surrounded by elevated, irregular ring, superficially similar to outer surface tubercles, equal-sized, arranged in continuous row along entire distal plate edge. Inner side of lateral arm plate ( Fig. 5B ) with large, oval to rounded triangular, well-defined but weakly prominent vertebral articular surface at some distance from inner dorso-proximal corner and separated from inwards protruding dorsal edge; tentacle notch small, deep, moderately well-defined, with shallow incision in ventral edge; seven small ambulacral groove spine articulations along entire ventral edge.

Paratype (supplements)

NRM PAL Ec38337 ( Fig. 5C–D ) is a dissociated median to distal lateral arm plate approximately 2.2 times as long as high, well in agreement with holotype except for straight to very weakly convex dorsal edge and ventral edge devoid of discernible ambulacral groove spine protrusions; three lateral spine articulations similar to those of holotype. Vertebral articular ridge on inner side longer and better defined than that of holotype; ambulacral groove spine articulations not clearly discernible; tentacle notch incision better defined than in holotype.

Remarks

The lateral arm plates of Ophiopetagno bonzo sp. nov. differ from those of all other species in having a conspicuous, coarse outer surface tuberculation. Similarities are most notable with the single unnamed lateral arm plate of Ophiopetagno sp. 2 from Hoburgen (see below), especially because of the outer surface ornamentation in O. bonzo . However, the dorsal edge is weakly convex rather than concave, the distal edge is oblique, the lateral spine articulations are smaller and almost indiscernible, and there are up to seven ambulacral groove spine articulations only in proximal lateral arm plates.

Occurrence

Nyhamn.

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.