Heterometra compta A.H. Clark, 1909b

Mohammednowshad, B., Idreesbabu, K. K., Parameswaran, Usha V., Messing, Charles G. & Sureshkumar, S., 2020, The Shallow-water Crinoid Fauna of Lakshadweep Atolls, North-western Indian Ocean, Zootaxa 4789 (1), pp. 247-265 : 257

Heterometra compta A.H. Clark, 1909b

Heterometra compta A.H. Clark, 1909b:636 ; 1941:293–295, pl. 33 (figs. 144–148); A.M. Clark & Rowe, 1971:8–9, 23.

Diagnosis.— A species of Heterometra with brachials wedge-shaped, not exceedingly short, and with ends not quite parallel. Enlarged proximal pinnules smooth, with proximal segments keeled. Cirri 23–25 mm long, of 31–35 seg- ments; longest cirrals about as long as broad or slightly longer than broad; distal cirrals with width to length ratio 1.5–2.0, with aboral tubercles. Arms 16–25, 125 mm long. P1 and P2 similar, equally long, with 26 segments; much longer and slightly stouter than PD. P3 scarcely longer than PD (A.H. Clark, 1941).

Material examined.— None in this study. Specimens were previously collected at Bassas de Pedro by RIMS Investigator (A.H. Clark, 1941) .

Distribution.— Bassas de Pedro, Lakshadweep. No depth recorded (A.H. Clark, 1941).

Remarks.— This species is currently known only from the nine specimens collected at Bassas de Pedro. It is unclear if H. compta was collected in shallow water (<50 m) or not. NIMA (2002) gives the depth range of Bassas de Pedro as 16.4– 3 m. Most records for the genus are <50 m, but species have been collected to depths of 125 m (possibly 136 m) (A.H. Clark, 1941; Messing & Tay, 2016), and RIMS Investigator also trawled and dredged in far deeper water (e.g., A.M. Clark & A.H. Clark, 1967). Heterometra compta is one of several species recorded from the western Indian Ocean and Red Sea that differ morphologically only in minor characters, many of which likely vary with growth and environmental conditions (e.g., arm number and length; cirrus length, and number and proportion of segments; aboral cirrus ornamentation, and relative lengths and numbers of segments of oral pinnules, and proportions of pinnule segments) (A.H. Clark, 1941; A.M. Clark, 1972; Marshall & Rowe, 1981). Three of these ( H. gravieri A.H. Clark, 1911c , and H. joubini A.H. Clark, 1911c , from Zanzibar, and H. ater (A.H. Clark, 1911c) from the Red Sea) remain known from one specimen each. All of these species require additional research to verify their status.