Asteronyx Müller & Troschel, 1842

Stöhr, Sabine, 2024, Taxonomic analysis of the genital plates and associated structures in Ophiuroidea (Echinodermata), European Journal of Taxonomy 933, pp. 1-98 : 24-25

Genus Asteronyx Müller & Troschel, 1842

Fig. 8

Type species

Asteronyx loveni Müller & Troschel, 1842 .

Examined species

Asteronyx loveni .

Oral GP

Absent.

Adradial GP

Half as long as in-disc part of arm. Flat, widest part half as wide as length, distally upwards curved, tapering to rounded proximal end. Terminating distally in a rounded condylar process with flat surface and at a small distance ventrally a half circle-shaped groove. Offset from fused abGP by longitudinal slits, not separating plates.

Abradial GP

Firmly fused to dorsal edge of adGP. Blade-like flat, longer than adGP, half as wide as adGP, abradial proximal half slightly depressed. Both GPs aligned along arm vertebrae with single flat surface.

Oral shields

Madreporite widely drop-shaped, externally with several small pores, inner side with deep middle depression, two irregular pores on either side. No regular oral shields.

Radial shield

Superficially appearing as long bar-like structures, consisting of a short distal part with widened end and for most of its length composed of multiple layers of thin, irregular, overlapping plates. Distal end with flat articular structure and a curved dorsal ledge. Proximally at a distance a round patch of finer mesh stereom. RS and adGP articulate by muscles and connective tissue, hard parts touching only at internal edge, evidenced by the wide gap between them in the relaxed disc.

Figures

Fig. 8. Asteronychidae Verrill, 1899, Asteronyx loveni Müller & Troschel, 1842. A=micro-CT; B–C =digital photos; D–J = SEM images. A–B. Radial shield and fused adradial and abradial genital plates in situ. C. Genital plates in situ. D. Genital plates, adradial view. E. Genital plates, abradial view. F. Radial shields, dissected from disc, distal ends fallen off. G. Detail of F, separating layers of radial shields. H. Radial shield distal end, inner aspect. I. Radial shield, distal end, outer side. J. Madreporite, inner aspect. Scale bars: A–G =1 mm; H–J =0.5 mm.