Echinocyamus megapetalus H.L. Clark, 1914

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 : 32-35

Echinocyamus megapetalus H.L. Clark, 1914

Figures 25–27

1914 Echinocyamus megapetalus H.L. Clark : p. 60; pl. 126.

1948b Echinocyamus megapetalus H. L. Clark. —Mortensen: p. 190–191; pl. 46: figs. 48–50.

Material studied. Nine denuded tests: WUSL/EI/152, EI/153, EI/154, EI/155, EI/156, EI/157, EI/195, EI/196, and EI/197 from Hiriketiya Bay, Sri Lanka.

Description. Shape and size —Test elongate, 3.72–7.35 mm TL; longer than broad, width, 73–80% TL; height, 41–45% TL; oral side deeply sunken, aboral side flattened.

Apical system —Situated close to centre, 50–56% TL from anterior margin; with four circular gonopores, single hydropore, sometimes distorted to resemble groove with two or three hydropores ( Fig. 26 ).

Ambulacra —Petaloid region length more than half TL (75–90% TL); petal III with 7–14 pore pairs, anterior paired petals with 5–12 pore pairs, posterior paired petals with 7–13 pore pairs; petals broad, open distally; pore series diverging; interporiferous zones wider than poriferous zones.

Peristome —Elongate pentagonal; moderate size, length 20–28% TL, width 16–22% TL, slightly anterior of centre, 38–42% TL from anterior margin, infundibulum deep.

Periproct —Small, 9–12% TL; transversely oval; wider than long, width 11–14% TL; inframarginal, 14–23% TL from posterior margin.

Geographic range. Indo-West Pacific, from Mauritius ( Clark 1914) to Coral Sea ( Miskelly 2002), South Pacific Islands ( Clark 1954; Mortensen 1948b) and Hawaiian Islands ( Mortensen 1948b).

Bathymetric range. 20–75 m ( Markello 2015).

Observed occurrence in Sri Lanka. Only denuded tests were found on the beach of Hiriketiya Bay, southern coast of Sri Lanka ( Fig. 27 ).

Remarks. E. megapetalus is recorded for the first time in Sri Lanka. E. megapetalus is similar to E. crispus in having a deep infundibulum but E. megapetalus is easily distinguished from E. crispus and other Indo-Pacific species by having broad, diverging petals that cover the majority of the aboral surface and by its deep infundibulum. However, studied specimens show great variation in test size and petaloid area length.

Figures

FIGURE 25. Echinocyamus megapetalus (WUSL/EI/195): A, aboral view; B, oral view; C, lateral view, right side.

FIGURE 26. SEM images showing details of apical system of Echinocyamus megapetalus: A, WUSL/EI/195; B, WUSL/EI/ 196; C, WUSL/EI/197.

FIGURE 27. Distribution map of Echinocyamus megapetalus, Fibularia ovulum and Fibularia sp. recorded in this study.