From editor or global species database
Diagnosis Salazar-Vallejo (2012): Body anteriorly swollen, with a posterior cylindrical cauda. Cephalic cage well developed. Dorsal shield rarely missing, extending over chaetigers 1–4 and often with an articulated anterior plate, rarely continued ventrally as a thinner coat. Body papillae small, capitate or clavate, in distinct belts, at least in anterior chaetigers. Anterior neuropodia with pseudocompound or with long transition hooks. Posterior neurohooks anchylosed, falcate, simple, sometimes flanged. Branchiae in two rows; distal row with four larger filaments, proximal row separated in two lateral groups, each with two or more filaments, often spirally arranged. Nephridial lobes between branchial rows. Posterior end with few neurohooks. Boring in hard or compact substrates. [details]
Etymology Chamberlin (1919) gives the etymology in a footnote as from Greek words, 'semio' (standard or flag) and 'dera' from the feminine Greek noun for neck [details]
Grammatical gender feminine as 'dera' is a feminine noun, and also indicated by subsequent authors who created species names which are feminine suffix adjectives. [details]