Fibularia ovulum Lamarck 1816
Creators: name: Tanaka, Hayate
name: Wakabayashi, Kaori
name: Fujita, Toshihiko
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Echinoidea
Clypeasteroida
Fibulariidae
Fibularia
Fibularia ovulum

description: Fibularia ovulum Lamarck, 1816
[Japanese name: Maru-mame-uni (Shigei 1986)]
Figs. 4, 6, 14; Tables 1, 2; Electronic Supplementary Table S1.
Fibularia ovulum Lamarck, 1816: 16; Mortensen 1948: 208 –210, figs, 102d, 104e, 106, 118, pl. 46, figs. 15–17, 21–24; A.M. Clark & Rowe 1971: 167 –170, fig. 83’, pl. 25, figs. 6–8; Liao and A.M. Clark 1995: 382 –383, fig. 224.
Fibularia craniolaris — H.L. Clark 1914: 57.
Material examined. 50 specimens, NSMT E-10393, dead tests, Kosyuku, Amami-Oshima Island, Kagoshima Prefecture, Japan (28°24′10″N, 129°28′04″E), beachcombing, coll. H. Tanaka, 22 Mar. 2015; 28 specimens, NSMT E-10392, dead tests, Vavvaru Island, Easter Beach, Lhaviyani Atoll, Maldives (5°25′4″N, 73°21′17″E), beachcombing, coll. A. Kroh and J. Herler, 7 Sept. 2014 – 14 Sept. 2014.
Diagnosis. Test outline slightly elliptical when viewed from above; height high; oral surface inflated toward the peristome. Periproct from round to elliptical. Petaloid region large; number of pores in petal III continues to increase with the test growth, reaching over 20 at TL> 5 mm. Diameter of genital pores equal to or smaller than that of petaloid pores in mature individuals. Two hydropores in an irregularly-shaped groove.
Description. The test is very small (TL = 2.05–9.45 mm) (Fig. 14), high (TH/TL = 0.59–0.84) (Fig. 14C), and elliptical when viewed from above (TW/TL = 0.77–0.92) (Figs. 14A, B). The test proportion hardly changes with the test growth (slope value is 1.0 between TW and TL, and 1.1 between TH and TL in the allometry regression; Table 1). The oral and aboral surfaces are inflated. There are no internal buttresses. Food grooves are absent (Fig. 14B). The ambulacra are almost the same width as the interambulacra (Figs. 14 D–F). The height of both ambulacral and interambulacral plates are lower than the width at the ambitus (Fig. 14F). The petaloid region is large (PL/TL = 0.49–0.69, PW/TW = 0.43–0.60). The ratio of petaloid region size to test size hardly change with the test growth (slope value is 1.0 between PL and TL, and 1.1 between PW and TL in the allometry regression). Each petal is composed of two almost parallel series of pore pairs lying oblique, and crossing the ambulacral plates (Fig. 14D). The number of pores of petal III, IV, and V is continuously increasing up to 30, 24, and 28, respectively, with the test growth (Fig. 4). The rate of increase slows down once a TL of more than 5.0 mm is reached. The pores become larger towards the distal tip of the petals.
The peristome, situated at the center of the oral side, is small (SL/TL = 0.12–0.23, SW/TW = 0.11–0.23) and slightly elongated antero-posteriorly (Figs. 14B, E). The ratio of peristome size to test size becomes smaller as test grows (slope value is 0.7 between SL and TL, as well as between SW and TL in the allometry regression). Two buccal pores are situated in each ambulacrum at the edge of the peristome. Single sphaeridium is fully enclosed within the test, and in the sphaeridial chamber in each ambulacrum near the peristome.
The round or roundish diamond shaped periproct is located halfway between the peristome and posterior margin of the test and is smaller than the peristome (AL/TL = 0.08–0.14, AW/TW = 0.09–0.15) (Figs. 14B, E). The ratio of peristome size to test size hardly changes as the test grows (slope value is 1.1 between AL and TL, and 0.9 between AW and TL in the allometry regression).
The apical system is situated at the midpoint of the anterior-posterior axis on the aboral surface (Figs. 14A, D). It consists of four genital pores, five ocular pores in small ocular plates, and two hydropores in a deep, irregularlyshaped groove. The diameter of the genital pores (<176 µm) is equal to or smaller than that of the largest petaloid pore (<ca. 150 µm). There is no obvious dimorphism in gonopore size (Fig. 6). The gonopores open in specimens as small as TL = 2.22 mm. The diameter of the ocular pores (ca. 40 µm) is much larger than that of the accessory pores (ca. 25 µm). Accessory pores are situated in oblique patches in the centers of ambulacral plates.
The primary tubercles are hemispherical, crenulate, and perforate. The diameters of oral and aboral primary tubercles are almost equal, ca. 150–200 µm. Their mamelons are constricted at the base. The miliary tubercles are hemispherical, poorly to non-crenulate, and indistinctly to non-perforate. They scattered around the primary tubercles. The diameters of oral and aboral miliary tubercles are almost equal, ca. 50 µm. The glassy tubercles occur between primary and miliary tubercles.
Color. The denuded test is whitish.
Distribution. This species is recorded from East Africa and the Red Sea, the Maldives, Bay of Bengal, Xisha Island, the Philippines, the East Indies to the Gilbert Islands, and south of the Tokara Islands, from 0–385 m depth (Shigei 1981; Liao & A.M. Clark 1995; present study).
description: Published as part of Tanaka, Hayate, Wakabayashi, Kaori & Fujita, Toshihiko, 2019, A new species of Fibularia from Japanese waters with a redescription of F. japonica and F. ovulum (Echinodermata: Echinoidea: Clypeasteroida), pp. 241-260 in Zootaxa 4543 (2) on pages 257-259, DOI: 10.11646/zootaxa.4543.2.4, http://zenodo.org/record/2617781