Thorsonia hedingi, Martins & Tavares, 2022

Martins, Luciana & Tavares, Marcos, 2022, Additions to the morphology of the Phyllophoridae and the Sclerodactylidae. I. Type species of Phyllophorella, Selenkiella, Cladolella and Clarkiella, with the description a new species of Thorsonia (Holothuroidea: Dendrochirotida), Zootaxa 5120 (4), pp. 559-572 : 566-567

Thorsonia hedingi sp. nov.

( Figures 8 – 9 )

Type material. Holotype: 11 mm ( ZMUC 324 as Thorsonia adversaria ), 6°35’ S; 105°41’ W, Sunda Strait , Indonesia, 29.vii. 1922, 30 m. Permanent slides of body wall ossicles ( MZUSP 2797 ).

Etymology. Named in honor of Svend Geisler Heding (cf. O’Loughlin et al., 2016) in recognition of his significant contributions to holothuroid systematics.

Diagnosis. Body wall with fusiform rods and tube feet tables with a solid spire.

Description. Body U–shaped. Tube feet restricted to ambulacra ( Fig. 8a ). Ten dendritic tentacles, ventral pair reduced. Anal papillae present. Longitudinal muscles split at anteriorly. Retractor muscles short ( Fig. 8b ), each attached to middle of the corresponding radial plate ( Fig. 8f ). Skin spiky, with spires of body wall tables protruding through, clearly visible to naked eye ( Fig. 7c ). Madreporite globular ( Fig. 8e ). Calcareous ring tubular with long posterior processes; radial plates smaller than interradials, laterally connected to each other for most of their length ( Fig. 8f ); both radial and interradial plates entirely subdivided ( Fig. 8g, h ). MidIR (IR5) smaller than adjoining interradials ( Fig.8i ), midR (RI) not modified. Interradial plates tapering anteriorly ( Fig. 8g, h ). AB marginal grooves deep, broad ( Fig. 8j ).

Body wall ossicles: tables and fusiform rods. tables with a 4- armed, perforated disc and a single solid central spire; arms entirely or partly perforated (200–350 μm long, 9a, b). Fusiform rods (200–800 μm long, 9c, d); perforated at the center and in the anal region two–pillared tables, with multilocular disc with a solid spire ending in a crown of spines (100–200 μm long Fig. 9e, f ). Tentacles and introvert with tables with multilocular disc and a central solid spire ending in 2–3 spines, disc irregular in outline (80–100 μm long, Fig. 9g, h ). Tube feet tables with arched disc and a central solid spire perforated at ends (50–80 μm long Fig. 9i, j ).

Remarks. The new species is herein assigned to Thorsonia Heding, 1940 , whose diagnostic characters are readily recognized in the new species. They are as follows: Body U shaped. Ten dendritic tentacles, ventral pair reduced. Tube feet restricted to the ambulacra. Calcareous ring tubular with long posterior prolongations comprising a mosaic of a series of large pieces. Body wall ossicles: 2–5 armed tables with a central spire and smaller multilocular tables with high spire, and fusiform rods. Tube feet with arched tables. The new species differs from both, T. adversaria and T. investigatoris by possessing fusiform rods in the body wall (fig. 9c, d) (absent in T. adversaria and T. investigatoris ). The new species also differs from T. fusiformis in having tube feet tables with solid spire (9j) whereas the tube feet tables have a perforated spire in T. fusiformis .

Figures

FIGURE 7. Selenkiella siamense Heding & Panning, 1954, holotype (ZMUC-HOL 250). Ossicles from body wall (a–b) table in (a) top and (b) bottom view; (c–d) rosettes from introvert; (e) plates and (f) end plate from tube feet.

FIGURE 8. Thorsonia sp. nov., holotype (ZMUC 324). (a) specimen in dorsal view; (b) retractor muscle (white arrow); (c) tables spikes from tube feet (white arrow); (d) detail from body wall with 4-armed tables; (e) madreporite; (f) photograph of the calcareous ring in outer view showing the RMA attachment; (g) photograph of the calcareous ring in outer view showing during bleach (h) drawing of the calcareous ring showing radial and interradial plates subdivided (i) photograph of the calcareous ring in outer view showing (IR 5) and (j) photograph of the calcareous ring in outer view showing AB. Abbreviations: Middorsal interradial plate (IR5); AB, aquapharyngeal bulb attachment; RMA, retractor muscle attachment. R, radial plate; IR interradial plate. Plate identity follows the system established by Ludwig (1889–1892).

FIGURE 9. Thorsonia sp. nov., holotype (ZMUC 324). Ossicles from body wall (a–f): (a–b) 4 armed tables; (c, d) fusiform rods; (e, f) tables from anal region; (g, h) tables from tentacles and introvert and tube feet table in lower view (i) and lateral view (j).