Phyrella Heding & Panning, 1954

Michonneau, François & Paulay, Gustav, 2014, Revision of the genus Phyrella (Holothuroidea: Dendrochirotida) with the description of a new species from Guam, Zootaxa 3760 (2), pp. 101-140 : 104-108

Phyrella Heding & Panning, 1954

– Phyrella Heding & Panning, 1954: 181 , type species: Phyllophorus trapezus Clark, 1932 , by original designation

= Thyonidiella Heding & Panning, 1954: 171 , type species: Thyonidiella oceana Heding & Panning, 1954 , by original designation; new synonymy

=? Semperiella Heding & Panning, 1954: 179 , type species: Orcula tenera Ludwig, 1875 , by original designation; synonymy with Thyonidiella by Rowe & Richmond, 2004; but see discussion under Phyrella? tenera .

Diagnosis. Small to medium-sized Phyllophoridae with 14–20 tentacles of varying size, typically arranged in an outer and inner circle; the tentacles can be paired or single, and are usually larger in the outer circle. Podia dispersed across body surface, numerous, cylindrical, 100–300 µ m in diameter, 1–3 mm in length, all with terminal suckers. Posterior end conical, gradually narrowing to a small cloaca, surrounded by 5 lightly-calcified podia developed as anal teeth. Calcareous ring with both radials and inter-radials with posterior prolongations, composed of multiple plates, closely associated along most of their lengths; anterior margins of radials unequally divided by well-formed notch serving for attachment of retractor muscles; anterior margins of inter-radials arrow-head shaped. Body wall ossicles of (1) tables with a circular/subrectangular disc, usually with 8 regular holes, with a smooth, sometimes slightly serrated rim, and spire with 4 pillars, connected by a single-cross beam, ending in a small, often incomplete crown; (2) rosettes, typically restricted to the introvert and cloacal regions, but sometimes more widespread. Tube feet with perforated plates developed as elongated perforated plates in addition to typical end plates; rosettes also present in podia of the cloacal region. Tentacles with rods. No ossicles detected in cloacal gut tract, cloacal retractor muscles, longitudinal muscles, respiratory trees, intestine. Single Polian vesicle. Single stone canal at least partially embedded in dorsal mesentery or membrane surrounding calcareous ring, ending in small, single madreporite. Gonads in two tufts, one on each side of dorsal mesentery. Respiratory trees extend entire length of animal. Evisceration through cloaca, not involving the pharyngeal complex, respiratory trees, gonads, but only the gut. Known only from shallow-waters (<10 m) of the Indo-West Pacific.

Remarks. Since the original recognition of Phyrella by Heding & Panning (1954), no species have been added to or removed from the genus. Heding & Panning (1954) erected Thyonidiella , Semperiella , and Phyrella in the same paper, differentiating them by the structure of the calcareous ring, number of tentacles, and presence/absence of body wall ossicles. They assigned Thyonidiella to their restricted Phyllophorinae , and the other genera to the newly erected Semperiellinae . The Semperiellinae were distinguished from the Phyllophorinae in having interradials fragmented into numerous pieces, although genera that include species with modest fragmentation of interradials (i.e., Lipotrapeza and Thyonidiella ) were retained in the latter. Such variability brings into question the taxonomic usefulness of this character. We also found variation in the degree of fragmentation of the inter-radials in Phyrella fragilis , with some smaller specimens (e.g., WAM Z26012) having unfragmented inter-radials.

The monotypic Thyonidiella was further differentiated from Semperiella by a perceived lack of body wall ossicles. However Heding & Panning (1954) apparently only examined the ventral body wall and Cherbonnier (1988) found tables in the dorsal body wall of the holotype of Thyonidiella oceana . Adding to the confusion was that Heding & Panning’s (1954) material on which they erected Thyonidiella oceana inadvertently included two species: the type from Ambon and two specimens (later referred to the newly erected T. cherbonnieri Rowe & Richmond, 2004 ) from Mauritius. Cherbonnier (1988), who did not realize that the Ambon specimen represented the holotype, considered the Mauritius species typical and referred the Ambon one to Semperiella tenera ( Ludwig, 1875) ( Rowe & Richmond, 2004) . Thus Cherbonnier’s (1988) subjective synonymy of Semperiella tenera with the holotype of Thyonidiella oceana renders Semperiella a synonym of Thyonidiella , as designated by Rowe & Richmond (2004) as first revisers. However none of these authors ( Heding & Panning, 1954, Cherbonnier, 1988, Rowe & Richmond, 2004) have examined the type of S. tenera ; our attempts to locate that type have also been unsuccessful.

The distinction between Semperiella and Phyrella was based on the number of tentacles: 15 in Semperiella and 20 in Phyrella . The number of tentacles in Phyrella is variable however, ranging between at least 15-20, rendering the distinction moot. Furthermore, examination of the holotype of Thyonidiella oceana revealed that it is a synonym of Phyrella fragilis , further supporting the synonymy of Semperiella and Phyrella . As first revisers, we select Phyrella as the senior synonym.

Phyrella is distinguished from the polytentaculate phyllophorid genera Lipotrapeza , Selenkiella , Phyllophorus and Anthochirus by its fragmented inter-radials elements, at least in adult stages. It is distinguished from the “semperielline” genera Cladolella , Pentadactyla , Neothyonidium , Neopentadactyla , Massinium by the presence of well-formed table ossicles in the body wall, with regular disc with typically 8 peripheral holes, a four-pillared spire united by a single cross-beam ending in an often incomplete crown.

Included species: After reviewing described species in relevant phyllophorid genera we consider 12 nominal species to be attributable to Phyrella or to have been assigned to Phyrella or to one of its synonyms in the past. Phyllophorus aculeata Ludwig, 1894 , Phyllophorus fragilis Mitsukuri & Ohshima, 1912 , Phyllophorus thyonoides Clark, 1938 , and Phyllophorus trapeza Clark, 1932 are currently assigned to Phyrella . Orcula tenera Ludwig, 1875 , Thyonidiella oceana Heding & Panning, 1954 , Thyonidiella exigua Cherbonnier, 1988 , Thyonidiella cherbonnieri Rowe & Richmond, 2004 , and Semperiella drozdovi Levin & Stepanov, 1999 are currently assigned to Thyonidiella . Finally, Phyllophorus bedoti Koehler, 1895 , Phyllophorus contractura Cherbonnier, 1988 , currently assigned to Phyllophorus ; and Lipotrapeza ambigua Cherbonnier, 1988 , currently assigned to Lipotrapeza , belong to this complex.

Based on the amended diagnosis for the genus, and after examining relevant type material, we propose that Phyrella includes the following species:

Phyrella trapeza ( Clark, 1932) ;

Phyrella drozdovi ( Levin & Stepanov, 1999) ;

Phyrella fragilis (Mitsukuri & Ohshima in Ohshima, 1912) of which Thyonidiella oceana Heding & Panning, 1954 is a junior synonym;

Phyrella mookiei sp. nov.;

Phyrella thyonoides ( Clark, 1938) .

Because original descriptions are not detailed enough, genetic material is lacking, or the type material is not located, we putatively assign these species to Phyrella , but additional data are needed to confirm this generic assignment:

Phyrella ? ambigua ( Cherbonnier, 1988) of which Thyonidiella cherbonnieri Rowe & Richmond, 2004 and Phyllophorus contractura Cherbonnier, 1988 are synonyms;

Phyrella ? bedoti ( Koehler, 1895) ;

Phyrella ? tenera ( Ludwig, 1875) .

Phyrella ? bedoti and Phyrella ? tenera are poorly known species with incomplete descriptions, their types are not located, and these names are currently not in use. We therefore suggest that they be treated as species inquirenda until they are re-described.

Finally, the following species have been attributed to Phyrella or to a genus we now consider a synonym of Phyrella , but do not belong there:

Orcula ( Phyllophorus ?) dubia Bedford, 1899 ;

Phyllophorus aculeatus Ludwig, 1894 ;

Thyonidiella exigua Cherbonnier, 1988 ;

Thyonidiella kungi O'Loughlin, 2012 .

Phyllophorus aculeatus is here transferred to the sclerodactylid genus Euthyonidiella . Generic assignment of the other remains unresolved, we provisionally place them in Phyllophorus sensu lato. Orcula ( Phyllophorus ?) dubia Bedford, 1899 is poorly known, the type appears to be lost, and the name is currently not in use. We suggest that it is treated as species inquirenda until it is re-described.

The characters that can be used to distinguish among the species attributable to Phyrella are listed in Table 3.