Echinoneus cyclostomus Leske, 1778

Arachchige, Gayashan M., Jayakody, Sevvandi, Mooi, Rich & Kroh, Andreas, 2019, Taxonomy and distribution of irregular echinoids (Echinoidea: Irregularia) from Sri Lanka, Zootaxa 4541 (1), pp. 1-100 : 11-14

Echinoneus cyclostomus Leske, 1778

Figures 5–9

Material studied. Three denuded tests: WUSL/EI/5, EI/6, and EI/7 from Hiriketiya, Sri Lanka.

Description. Size and shape —Test ovoid, small to medium-sized, 20.4–36.6 mm TL; width 75–85% TL, height 48–50% TL.

Apical system —Tetrabasal; four gonopores, situated close to centre of aboral surface, approximately 50% TL from anterior margin of test.

Ambulacra —Non-petaloid; interporiferous zone distinctly elevated; pore zones depressed and narrow; pores larger on aboral surface.

Tuberculation —Primary tubercles imperforate and non-crenulate, primary tubercles on oral surface larger than aboral ones; miliary tubercles more or less evenly distributed among primary tubercles; numerous, densely distributed glassy tubercles on aboral surface, equal in size to primary tubercles; tuberculation of interporiferous zone in ambulacra similar to that in interambulacra.

Peristome —Small relative to periproct; length c. 15% TL, width c. 20% TL; irregularly oval to triangular; slightly pointed towards interambulacra 2 and 4; moderately sunken; situated approximately 46% TL from anterior margin of test to anterior edge of peristome.

Periproct —Large, length 23–25% TL, width 14–16% TL; teardrop-shaped, pointed towards peristome, anterior-posteriorly elongated; situated posteriorly, approximately 15% TL from posterior margin of test.

Geographic range. Indo-West Pacific, from West Indies, South East Arabia ( Mortensen 1948c), Mauritius (de Loriol 1883; Clark 1925a), Maldives area ( Bell 1909; Koehler 1922), Sri Lanka ( Bell 1887a; Herdman et al. 1904), Bay of Bengal ( Bell 1887b; Clark 1925a), North Australia ( Clark 1938) and East Indies ( Clark 1950) to China & South Japan ( Mortensen 1948a), Philippine Islands ( Clark 1949), South Pacific Islands (Clark 1952) and Hawaiian Islands ( Clark 1925b).

Bathymetric range. 0–120 m ( Rowe & Gates 1995).

Observed occurrence in Sri Lanka. Dead specimens were collected on the shore among biogenic sands at Hiriketiya and Polhena Beach along the southern coast of Sri Lanka ( Fig. 9 ). This species was first recorded from Sri Lanka by Bell (1882), then by Clark (1925a) and recently recorded by Fernando (2006). The bathymetric range of this species in Sri Lanka is 0– 100 m.

Remarks. Test shape of the largest specimen (WUSL/EI/5) found in the present study differs from the other two studied specimens. Differences include a more rounded test, truncated posterior margin, abnormalities in the pore zones of ambulacra I, II and III which narrow towards the interporiferous zone close to the apical system, and robust test (Fig. 5). The apical system of this specimen is located approximately half-way (51% TL) towards the posterior from the anterior margin of the test. The distorted symmetry of the specimen suggests that it may has been damaged by at some stage during its life, but almost completely regenerated the damage. However, a similar observation has been recorded by Mortensen (1948a: 78) in E. abruptus H.L. Clark, 1925 (subjective junior synonym of E. cyclostomus ).

Figures

FIGURE 9. Distribution map of Echinoneus cyclostomus recorded in this study.