Euthyonidiella aculeata
Creators: name: Michonneau, François
name: Paulay, Gustav
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Sclerodactylidae
Euthyonidiella
Euthyonidiella aculeata

description: Euthyonidiella aculeata (Ludwig, 1894)
Figures 25–26, 27 i
Phyllophorus aculeatus Ludwig, 1893 a: 111 1893b: 183: nomen nudum
Phyllophorus aculeatus Ludwig, 1894: 128–129, pl. XIII, fig 6–11. Holotype: USNM 18171; type locality: Gulf of Panama, shore
Phyllophorus aculeatus: Deichmann, 1941: 133–134, pl. 25; fig. 1–3
Phyrella aculeata: Heding & Panning, 1954: 184–185, fig. 89
Material examined: USNM 18171 (Holotype), Gulf of Panama, 12 March 1891.
Description. External morphology. Body wall rough like sand paper, fairly contracted, uniformly light gray (Fig. 25). Body cylindrical with ends tapering bluntly; 60 mm along dorsum, 65 mm along venter, and 25 mm wide at mid-body. Tube feet same color as body wall, most are retracted, very abundant, cover both radial and interradial areas without any clear arrangement. Introvert retracted, short (7 mm long, 3 mm wide), light gray. Tentacles vary in size between 2 and 22 mm long; exact number and arrangement cannot be discerned given the state of preservation of the specimen. No anal teeth.
Internal anatomy. Three Polian vesicles (4–16 mm), thin, light brown. Stone canal and madreporite not observed. Most of the intestine and sections of the dorsal mesentery have been removed from the animal and are in the jar. Gonads in two tufts, formed by brown tubes that branch a few times, mostly near origin, up to 25 mm in length. Intestine fairly long, empty. Respiratory tree, only left side remaining, dense, extending almost entire length of animal.
Calcareous ring. Calcareous ring with narrow radials and inter-radials, formed by barely fragmented elements, embedded in a fairly thick membrane (Fig. 27i). Anterior margins of radials straight, lightly notched at center. Anterior margins of inter-radials acutely pointed, arrow-head shaped. Inter-radials lie on top of radials, due to contraction of the structure. Radials project posteriorly forming short tails. Inter-radials lack posterior projections.
Ossicle assemblage. Dorsal body wall with two types of tables. Regular tables (Fig. 26b–d) with disc nearly circular or ellipsoidal, 90–105 µ m in diameter, 8–12 holes arranged in one circle with sometimes 2–4 smaller holes at the periphery, with complete rim; spire formed by four pillars united by a single cross-beam, with continued projections usually forming well-developed, spiny crown with a central hole. Podia with large tack-like tables (Fig. 26a,f), with a convex, elongated, elliptical disc that is perforated by a large central hole, up to 250 µ m in diameter, and 10–15 smaller, scattered holes; spire 120–230 µ m high, with four pillars that are fused along much of their length, but leave occasional perforations, usually ending bluntly, compressed in same plane as disc.
Remarks. This species is known only from the holotype, reexamined and further reported on by Deichmann (1941), who confirmed its uniqueness. The calcareous ring has not been previously illustrated. In the original description Ludwig notes that the anterior end of the radials are pointy, monocuspid, slender and are not typical of other Orcula and Phyllophorus. Indeed, the calcareous ring has the structure of a sclerodactylid, rather than a phyllophorid. The regular tables in the body wall are somewhat similar to Phyrella and other genera including Phyllophorus, but are more regular and ellipsoidal than in other Phyrella. Furthermore, no species of Phyrella have the large, tack-like tables that occur in the tube feet of E. aculeata, or have three Polian vesicles, and all have anal teeth unlike this species. Euthyonidiella aculeata lacks perforated plates, and rosettes in the introvert and cloacal body wall, contrary to Phyrella. These characters, together with the distant occurrence (in the East Pacific, rather than Indo-West Pacific) indicate that this species is not attributable to Phyrella and differs from other genera as well.
The calcareous ring, regular tables, and tack-like tables are all similar to species of the sclerodactylid genus Euthyonidiella Heding & Panning, 1954, and we transfer P. aculeatus to that genus. The only other polytentaculate phyllophorid known from the East Pacific, Phyllophorus zacae Deichmann, 1938, was also transferred to Euthyonidiella by Heding & Panning (1954).
description: Published as part of Michonneau, François & Paulay, Gustav, 2014, Revision of the genus Phyrella (Holothuroidea: Dendrochirotida) with the description of a new species from Guam, pp. 101-140 in Zootaxa 3760 (2) on pages 133-135, DOI: 10.11646/zootaxa.3760.2.1, http://zenodo.org/record/4908324