Amamiichthys, Tanaka, Fumiya & Iwatsuki, Yukio, 2015

Tanaka, Fumiya & Iwatsuki, Yukio, 2015, Amamiichthys, a new genus for the sparid fish Cheimerius matsubarai Akazaki 1962, and redescription of the species, with designation of a neotype, Zootaxa 4007 (2), pp. 195-206 : 196-199

Amamiichthys new genus

Figures 1 A–3A, 4; Table 1

Type species. Cheimerius matsubarai Akazaki 1962:132 , 347, fig. 31 (Amami-oshima Island, Ryukyu Islands, Japan)

Diagnosis. A new genus of Sparidae with the following combination of characters (Table 1): both jaws with a single outer row of molariform teeth, upper jaw with two inner rows of small molariform teeth, teeth on anteromedial aspect of lower jaw small, villiform, becoming molariform posteriorly ( Fig. 1 A); supraoccipital crest with somewhat thickened uppermost edge (frontal view) ( Fig. 2 A-4); frontal bone flat, coarse and porous ( Fig. 2 A- 5); upper ethmoid with strongly bifurcate protuberance just beneath mid-region of anteriormost portion of frontal bone (frontal view) ( Fig. 2 A-8); head and body pinkish, gradually becoming silvery toward abdomen, with many small blue spots, some pairs overlapping ( Figs. 3A , 4 ).

Remarks. The genus Cheimerius (type species: Dentex nufar Valenciennes 1830 ) was proposed by Smith (1938), who recognized the following distinguishing characters ( Fig. 3 B): four canines on the upper jaw, six pairs (middle pair always small) on the lower jaw; one row of conical teeth laterally on both jaws; third to sixth dorsalfin spines filamentous; head scales extending to median part of interorbital space. Subsequently, Akazaki (1962) described Cheimerius matsubarai on the basis of two specimens (holotype and paratype) from Amami-oshima Island, Ryukyu Islands, Japan, which shared the above generic diagnostic characters. Both species have since remained unquestioned in Cheimerius .

However, our examination of the jaw teeth of C. matsubarai showed their morphology could be better described as small molariform ( Fig. 1 A), rather than conical ( Fig. 1 B), a feature overlooked by Akazaki (1962). Subsequent examination of the skull morphology of both C. matsubarai and C. nufar showed the former to have a somewhat thickened uppermost edge on the supraoccipital crest (frontal view) ( Fig. 2 A-4; vs. thin overall in C. nufar ; Fig. 2 B-4), the anterodorsal surface of the anterior frontal bone flat and porous ( Fig. 2 A-5; vs. thick and slightly protuberant, Fig. 2 B-5), and the uppermost ethmoid region with a large and strongly bifurcate protuberance ( Fig. 2 A-8; vs. small and weakly bifurcate, Fig. 2 B-8).

A recent molecular study of sparid fishes, based on the cyt- b gene, indicated that C. nufar and C. matsubarai did not group in the same clade ( Chiba et al. 2009, Figs. 2 , 3 ) ( Fig. 5 , after Chiba et al. 2009). Cheimerius nufar conformed to the A-5 clade ( Fig. 5 ), including Eastern Atlantic members of Pagrus and Dentex , characterized by filamentous dorsal-fin spines. Furthermore, Atlantic species of Pagrus and three species of Pagellus conformed to the A-4 clade ( Fig. 5 ), having somewhat robust dorsal-fin spines. However, C. matsubarai belonged to the A-3 clade ( Fig. 5 ) (which includes Indo-West Pacific species of Argyrop s, Evynnis and Pagrus ), and is characterized by red body coloration. Thus, we concluded that C. matsubarai should not be included in the A-5 clade ( Fig. 5 ).

TABLE 1. Comparison of selected characters from five sparid genera, Amamiichthys , Cheimerius , Argyrops , Evynnis , and Pagrus .

Amamiichthys Cheimerius Argyrops * Evynnis ** Pagrus from western

Pacific*** Dorsal-fin rays XII, 10 XII, 10 XI–XII, 10 XII, 10 XII, 10 Anal-fin rays III, 8 III, 8 III, 8 III, 9 III, 8 Pored lateral line scales 58–61 57–64 48–52 58–61 54–60 Fresh body color pinkish, gradually pinkish or rosy with 5 pinkish pinkish, gradually pinkish, gradually becoming silvery toward broad dark red becoming silvery becoming silvery toward abdomen, with many blue cross-bands toward abdomen, with abdomen, with many tiny spots, sometimes paired many tiny blue spots blue spots, sometimes and slightly overlapping paired and slightly overlapping

Specimens of Argyrops bleekeri and A. spinifer examined (see Comparative material)

Specimens of Evynnis cardinalis and E. tumifrons examined (see Comparative material)

*** The genus Pagrus from the western Pacific requires taxonomic revision ( Iwatsuki et al. 2013: p. 109)

In addition to body coloration, C. matsubarai is generally similar to Argyrops , Evynnis and the Pacific Pagrus in having molariform teeth on both jaws and head scales extending to the interorbital region. However, C. matsubarai is considered to be distinct from species of those three genera on the basis of different external and internal characters (Table 1).

Cheimerius matsubarai is most similar to congeners of Evynnis in overall appearance, including red body coloration, first and second dorsal-fin spines short, and third and fourth dorsal-fin spines elongated. However, C. matsubarai differs from Evynnis in having eight anal-fin soft ray (vs. nine in Evynnis ), a single outer row of molariform teeth along each jaw, two rows of small molariform teeth medially on the upper jaw, the lower jaw anteromedial teeth villiform, becoming small molariform posteriorly (vs. two rows of conical teeth, gradually becoming blunt posteriorly on both jaws), ethmoid large, bifurcate (frontal view) ( Fig. 2 A-8; vs. very small, weakly bifurcate, Fig. 2 D-8), anterodorsal surface of frontal flat, porous ( Fig. 2 A-5; vs. entire frontal porous, Fig 2 D-5), and a somewhat thickened uppermost edge on the supraoccipital crest (frontal view) ( Fig. 2 A-4; vs. anterior part of supraoccipital crest hypertrophic, Fig. 2 D-4).

Cheimerius matsubarai differs from Pacific Pagrus species in having the first and second dorsal-fin spines very short, and the third and fourth dorsal-fin spines extremely elongated (vs. third and fourth gradually longer in Pacific Pagrus ), the anterodorsal surface of the frontal porous ( Fig. 2 A-5; vs. anteriorly convex, with a medial suture, Fig. 2 E-5), and the anterodorsal surface of the ethmoid large and strongly bifurcate ( Fig. 2 A-8; vs. large, non-bifurcate, Fig. 2 E-8).

Cheimerius matsubarai is discernible from Argyrops in having many small blue spots, some pairs slightly overlapping, dorsolaterally on the body ( Figs. 3A , 4 ; vs. absent in Argyrops ), as well as in teeth (vs. two rows of large molariform teeth, gradually becoming larger posteriorly in Argyrops ), anterodorsal frontal ( Fig. 2 A-5; vs. protuberant and medially robust without pores in Argyrops , Fig. 2 C-5) and ethmoid conditions ( Fig. 2 A-8; vs. large and non-bifurcate in Argyrops , Fig. 2 C-8).

Because the above comparisons indicated strong generic divergence, the new generic name Amamiichthys is proposed (type species: Cheimerius matsubarai Akazaki, 1962 ).

Etymology. The new generic name reflects the extremely limited distribution of the type species A. matsubarai , which is known only from Amami-oshima Island, Ryukyu Islands, Japan ( Fig. 6 ).

Figures

FIGURE 1. Teeth of upper and lower jaws. A. Amamiichthys matsubarai, MUFS 30983, 257 mm SL, Amami-oshima Island, Japan; B. Cheimerius nufar, MUFS 22693, 236 mm SL, Oman.

FIGURE 2. Neurocranium (anterior view). A. Amamiichthys matsubarai, MUFS 30983, 257 mm SL. B. Cheimerius nufar MUFS 21009, 229 mm SL. C. Argyrops spinifer, MUFS 134, 236 mm SL. D. Evynnis tumifrons, MUFS 11740, 216 mm SL. E. Pagrus major, MUFS 22504, 206 mm SL. Numbers indicate partial bones of neurocranium. 1, ethmoid; 2, lateral ethmoid; 3, vomer; 4, supraoccipital crest; 5, frontal; 6, sphenotic; 7, pterotic; 8, articulating facet for palatine, olfactory foramen; 9, uppermost ethmoid. Scale = 5 mm.

FIGURE 4. Diagnostic coloration of dorsolateral body surface of Amamiichthys matsubarai. MUFS 43227, 212 mm SL, Amami-oshima Islands, Japan.

FIGURE 5. Phylogenetic tree of maximum likelihood analyses conducted on 123 n data set under the GTR + I + Γ model (expanded portion showing Clade A) (after Chiba et al. 2009, fig. 2). Major distribution legend as follows: WA, Western Atlantic; EA, Eastern Atlantic; SeA, Southeastern Atlantic; M, Mediterranean; WI, Western Indian Ocean; I-WP, Indo-West Pacific; WP: Western Pacific.

FIGURE 6. Collection localities of Amamiichthys matsubarai along the coast of Amami-oshima Island, Ryukyu Islands, Japan.

FIGURE 3 A. Amamiichthys matsubarai, MUFS 30984, neotype, 268 mm SL, Amami-oshima Islands, Japan. B. Cheimerius nufar, 250 mm SL, Durban, South Africa, photographed by J. E. Randall.