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) Author Martins, Luciana 0000-0002-8107-3265 Museu de Zoologia, Universidade de São Paulo, São Paulo-SP, 04263 - 000, Brazil. & martinsrluciana @ gmail. com, mdst @ usp. br; https: // orcid. org / 0000 - 0002 - 8107 - 3265 mdst@usp.br Author Tavares, Marcos 0000-0002-7186-5787 Museu de Zoologia, Universidade de São Paulo, São Paulo-SP, 04263 - 000, Brazil. & https: // orcid. org / 0000 - 0002 - 7186 - 5787 text Zootaxa 2022 2022-03-29 5120 4 559 572 journal article 20049 10.11646/zootaxa.5120.4.6 a0421c84-a047-4499-b92f-52cab23d6e79 1175-5326 6392907 58CAB25D-CA92-44EE-BF1D-67DB91EB9596 Selenkiella siamense Heding & Panning, 1954 ( Figures 5 – 7 ) Material examined. Holotype : Ko Kradat , Thailand , 8–10 m , 27.i. 1900 , 45 mm length ( ZMUC –HOL– 250) . Paratype : Koh Kram , Thailand 25.ii. 1900 , 50 mm length ( ZMUC –HOL–251) . Redescription. Body barrel-shaped; tube feet scattered throughout body ( Fig. 5a ). Color, in ethanol, gray. 25 dendritic tentacles arranged in 2 circles (15 + 10): 15 in outer circle, 10 in inner circle. Anal papillae present. Longitudinal and circular muscles well developed ( Fig. 5b ). Longitudinal muscle split at anterior end ( Fig. 5b ). Retractor muscle short, attached to middle of radial plate. FIGURE 5. Selenkiella siamense Heding & Panning, 1954 , holotype (ZMUC-HOL 250). (a) specimen in lateral view; (b) top view of tentacles; (c) photograph of the calcareous ring in outer view. Abbreviations: RM, retractor muscle, CM, circular muscle, LM, longitudinal muscle. Plate identity following Ludwig (1889 –1892). FIGURE 6. Selenkiella siamense Heding & Panning, 1954 , paratype (ZMUC-HOL 251). μCT volume rendering of calcareous ring (a–c) outer view, (d) oblique view, (e) inner view, (f) transverse cross-section at the top region. Unlabeled arrows in (e) point to groove for water vascular system canals. Abbreviations: AB, aquapharyngeal bulb attachment; IR, interradial plate; LMA, longitudinal muscle attachment; midIR, mid-dorsal interradial plate; midR, mid-ventral radial plate; R, radial plate; RMA, retractor muscle attachment. Plate identity follows the system established by Ludwig (1889 –1892). Calcareous ring robust. Radial plates slightly taller, much larger than interradial ones. Interradial plate articulated with base of radial plate and first piece of posterior process, such that half of interradial plate is connected to the posterior process ( Figs. 5c ; 6a ). MidIR (IR5) and midR (RI) not modified ( Fig. 6b, c , respectively). Radial plates undivided, rectangular, base convex, without projection, two AP, one wider than the other ( Fig. 6 a; c ). Posterior processes longer than radial plates, subdivided into about 3 – 4 large pieces ( Figure 5c ). Interradial plates elongated, with straight ( Fig.6 ) or slightly concave base ( Fig. 6b ) and pointed anterior end. Marginal grooves for AB deep ( Fig. 6e ). TCT rectangular ( Fig. 6f ). Body wall with four–pillared tables with circular disc (70–100 μm long; Fig.7 a,b ); disc with one large central hole, eight marginal perforations, margin undulated; spire ending in 8–12 spines. Introvert with rosettes (30–80 μm long; Fig.7c, d ). Tentacles with rods branched or perforated at both ends (former 50–100 μm long;latter 40–100 μm long). Tube feet with flat perforated plates, with irregular margins (140–200 μm long; Fig.7e ) and endplate with minute holes, larger around margin and smaller medially (endplates up to 300 μm diameter; Fig.7f ). 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. Remarks. The following illustrations are additions to the data provided by Heding & Panning (1954) : the aquapharyngeal bulb attachment; longitudinal muscle attachment and retractor muscle attachment (fig 6d), the grooves in the radial plate for water vascular canals (fig 6e) and transverse cross-sections at the top region (fig 6f). We also provide a photograph of the general aspect of the body ( Fig. 5a ) and described for the first time by means optical microscopy the morphology of the longitudinal retractor and circular muscles Fig. 5b .