Plectranthias fourmanoiri Randall

Plectranthias fourmanoiri Randall

Figures 16, 21; Tables 1–16, 24

Common name: Fourmanoir’s Perchlet

Plectranthias fourmanoiri Randall 1980: 125, fig. 7, tab. 7 (type locality: Enewetak Island, Marshall Islands; paratypes from Christmas Island).— Allen & Steene 1988: 180, fig. 133 (checklist, photo, Christmas Island).— Allen 2000: 87 (checklist, Christmas Island).— Allen & Erdmann 2012: 288 (diagnosis, photo, Christmas Island).— Hobbs et al. 2014a: 194, tab. 1 (checklist, Christmas Island).— Anderson 2018: 27 (checklist). — Parenti & Randall 2020: 25 (checklist).

Diagnosis. The following combination of characters distinguishes P. fourmanoiri from congeners: palatines edentate; dorsal segmented rays usually 16–18 (rarely 20); fourth or fifth dorsal spine longest; pectoral rays 12–13, all unbranched; predorsal scales extend anteriorly only to vertical through mid-pupil; lateral line complete or interrupted, with 15–26 + 0–4 tubed scales. It is also distinctive in having a large black spot on the middle portion of dorsal fin, one near the end of the the dorsal fin, one over the base of the last four anal rays, and one mid-ventrally on the abdomen in front of the anus.

Remarks. A relatively small species (largest specimen 39.5 mm SL), P. fourmanoiri was previously known in Australia only from Christmas Island. We here record it from Holmes Reef, Coral Sea, based on a specimen collected for the aquarium trade by Cairns Marine collecter Cale Bennett. A photograph of the specimen is provided in Figure 21. The species is otherwise known from oceanic islands throughout the West Pacific, ranging as far east as the Pitcairn Islands (Randall 1980). Randall and subsequent authors (e.g., Allen & Erdmann 2012, Tashiro & Motomura 2017) record the species as having a complete lateral line consisting of 25 tubed scales. However, three specimens examined by us (two from Morane, French Polynesia, and one from Henderson Island, Pitcairn Islands) have incomplete or interrupted lateral lines bilaterally. The remaining two specimens have complete lateral lines, though one has 26 rather than 25 tubed scales on one side. One of the specimens has 20 segmented dorsal rays (previously known variation 16–18).

We add the following new observations: scales with peripheral cteni; vertebrae 10+16; supraneurals 2; predorsal formula 0/0/2/1+1; dorsal pterygiophores in interneural spaces 9–13 1/1+1/1+1/1+1/1+1 or 1/1/1+1/1+1/1+1; no trisegmental pterygiophores associated with dorsal fin; terminal dorsal pterygiophore in interneural space 17–18; 3–4 trisegmental pterygiophores associated with anal fin; terminal anal pterygiophore in interhaemal space 4–5; ribs present on vertebrae 3 through 9–10; epineurals present on vertebrae 1 through 10; parhypural and hypurals autogenous; well-developed hypurapophysis on parhypural; epurals 3; single uroneural (posterior uroneural absent); ventral tip of cleithrum with well-developed posteroventral process; proximal tip of first anal-fin pterygiophore near distal tips of parapophyses on vertebra 10.

Morphometric data are summarised in Table 24.

Material examined. Christmas Island, Australia. WAM P.28990-009, 2: 18.9–22.7 mm SL, Indian Ocean, Australia, Christmas Island, 10°26′S, 105°40′E, 15–20 m, G. R. Allen & R.C. Steene, 20 Jun 1986. French Polynesia. AMS I.46488-013, 21.2 mm SL, Morane, 23°10.2′S, 137°09.2′W, 33 m, A. Reid, 10 Oct 2014; AMS I.46490- 016, 29.4 mm SL (subsequently cleared and stained), Morane, 23°10′S, 137°09.2′W, 20 m, S.E. Reader, 10 Oct 2014. Pitcairn Islands. AMS I.17900-001, 39.5 mm SL, Henderson Island, 24°21′S, 128°19′W, 49 m, J.E. Randall et al., 18 Jan 1971; USNM 212176, 36.9 mm SL (paratype, radiograph only), off southwest side of Ducie Atoll, J.E. Randall et al. 15 Jan 1971.