Heterometra A.H. Clark, 1909d

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 : 256-257

Heterometra A.H. Clark, 1909d

Type species.— Antedon quinduplicava Carpenter, 1888 .

Diagnosis.—A genus of Himerometridae with more than ten arms in fully developed individuals; cirri moderately long with aboral tubercle or spine on distal segments and terminal claw always strongly curved; distal cirrus segments usually shorter than proximal, or both distal and proximal cirrus segments short; proximal brachial pinnules increasing in length and robustness from P1 to P3; enlarged proximal pinnules elongated, slender or rather stout, smooth or with basal keel, or with distal segments each bearing spines or flange-like projection (A.H. Clark, 1941).

Remarks.— Heterometra currently includes 27 accepted species. However, eight are known from only three or fewer specimens (four from one specimen each), and several are distinguished on the basis of minor morphological, often apparently ontogenetic, differences (e.g., arm number, cirrus and proximal pinnule length, or proportions of cirrals or pinnulars) (A.H. Clark, 1941; Messing & Tay, 2016).