Falsanathelges, Boyko & Williams, 2003

Shinoda, Haruki, Fujita, Hiroki, Nakano, Tomoyuki & Shimomura, Michitaka, 2025, First record of Falsanathelges Boyko & Williams, 2003 (Crustacea: Isopoda: Epicaridea: Bopyridae) from Japan, with the description of a new species, Zootaxa 5594 (1), pp. 155-166 : 156-165

Genus Falsanathelges, Boyko & Williams, 2003

Anathelges : Nierstrasz & Brender à Brandis, 1931: 195

(not Anathelges Bonnier, 1900 )

Falsanathelges : Boyko & Williams, 2003: 801–802.

Amended Diagnosis (modified from Boyko & Williams 2003). Female: body longer than broad, not distorted. Head with anterior margin concave or convex, lateral and posterior margins convex. No oostegites extended over head or produced posteriorly. Pereomeres 1–3 anteriorly concave and posteriorly convex, pereomeres 6 and 7 anteriorly convex and posteriorly concave. Pleomeres 1–5 with elongate-ovate biramous pleopods and uniramous lateral plates, all arising from common peduncle. Pereopod 1 anterior to head, pereopod 2 parallel to head, no large gaps between pereopods 4–7. All pleopods broad and flat, not narrow and rounded. Pleotelson with uniramous or biramous uropods.

Male: body lateral margins of pereomeres 1 and 2 shorter than those of pereomeres 3–7. Head approximately twice as wide as long, anterior margin smoothly convex. Pereomeres separated. Pleomeres fused into single segment. Pleopods and uropods lacking.

Type Species. Falsanathelges muelleri (Nierstrasz & Brender à Brandis, 1931).

Included Species. Three: F. muelleri (Nierstrasz & Brender à Brandis, 1931); F. mariae Williams & Boyko, 2016 ; F. grandiceps sp. nov.

Remarks. Falsanathelges is distinguished from Anathelges by the following features (those of Anathelges given in parentheses): head subequal or longer than broad in female (longer than broad), anterior margins of head concave or convex in female (convex), body not distorted in female (distorted), no oostegites extended over head and produced posteriorly in female (oostegite extended over head and produced posteriorly), pereomeres 1–3 anteriorly concave and posteriorly convex in female (pereomeres 1–5 anteriorly concave and posteriorly convex), pereopod 1 anterior to head in female, pereopod 2 parallel to head in female (pereopods 1 and 2 anterior to head, pereopod 3–5 parallel to head), no broad gap between pereopods 5 and 6 in female (broad gap between pereopods 5 and 6), pleopods broad and flat in female (pleopods narrow and cyrindorical), pleotelson with uniramous or biramous and pedunculate uropods in female (with uniramous and non-pedunculate uropods), the shape of the lateral pereomeres distally rounded in male (at least some pereomeres distally truncated).

Although Falsanathelges and Anathelges differ in many taxonomically informative characters, they both exhibit five pairs of biramous pleopods and uniramous lateral plates arising from a common peduncle ( Boyko & Williams 2003).

Key to species of Falsanathelges (Based on females)

1 Uropods biramous.................................................................................... 2

- Uropods uniramous............................................. Falsanathelges mariae Williams & Boyko, 2016

2 Head approximately one-seven of body length, anterior margin concave and base of uropods with peduncle................................................................ Falsanathelges muelleri (Nierstrasz & Brender à Brandis, 1931)

- Head approximately one-fourth of body length, anterior margin convex and base of uropods without peduncle.................................................................................... Falsanathelges grandiceps sp. nov.