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

publication ID

https://dx.doi.org/10.11646/zootaxa.4007.2.3

publication LSID

lsid:zoobank.org:pub:4CE1B3B6-8D31-4ADA-AEE8-1857962D0CDB

DOI

https://doi.org/10.5281/zenodo.5630294

persistent identifier

https://treatment.plazi.org/id/537299DD-FC0C-4508-8800-BF04AC97906A

taxon LSID

lsid:zoobank.org:act:537299DD-FC0C-4508-8800-BF04AC97906A

treatment provided by

Plazi

scientific name

Amamiichthys
status

new genus

Amamiichthys new genus

Figures 1 View FIGURE 1 A– 3 A, 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 View FIGURE 1 A); supraoccipital crest with somewhat thickened uppermost edge (frontal view) ( Fig. 2 View FIGURE 2 A- 4); frontal bone flat, coarse and porous ( Fig. 2 View FIGURE 2 A- 5); upper ethmoid with strongly bifurcate protuberance just beneath mid-region of anteriormost portion of frontal bone (frontal view) ( Fig. 2 View FIGURE 2 A- 8); head and body pinkish, gradually becoming silvery toward abdomen, with many small blue spots, some pairs overlapping ( Figs. 3 A View FIGURE 3 A , 4 View FIGURE 4 ).

Remarks. The genus Cheimerius (type species: Dentex nufar Valenciennes 1830 ) was proposed by Smith (1938), who recognized the following distinguishing characters ( Fig. 3 View FIGURE 3 A 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 View FIGURE 1 A), rather than conical ( Fig. 1 View FIGURE 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 View FIGURE 2 A- 4; vs. thin overall in C. nufar ; Fig. 2 View FIGURE 2 B- 4), the anterodorsal surface of the anterior frontal bone flat and porous ( Fig. 2 View FIGURE 2 A- 5; vs. thick and slightly protuberant, Fig. 2 View FIGURE 2 B- 5), and the uppermost ethmoid region with a large and strongly bifurcate protuberance ( Fig. 2 View FIGURE 2 A- 8; vs. small and weakly bifurcate, Fig. 2 View FIGURE 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 View FIGURE 2 , 3 View FIGURE 3 A ) ( Fig. 5 View FIGURE 5 , after Chiba et al. 2009). Cheimerius nufar conformed to the A- 5 clade ( Fig. 5 View FIGURE 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 View FIGURE 5 ), having somewhat robust dorsal-fin spines. However, C. matsubarai belonged to the A- 3 clade ( Fig. 5 View FIGURE 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 View FIGURE 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 View FIGURE 2 A- 8; vs. very small, weakly bifurcate, Fig. 2 View FIGURE 2 D- 8), anterodorsal surface of frontal flat, porous ( Fig. 2 View FIGURE 2 A- 5; vs. entire frontal porous, Fig 2 View FIGURE 2 D- 5), and a somewhat thickened uppermost edge on the supraoccipital crest (frontal view) ( Fig. 2 View FIGURE 2 A- 4; vs. anterior part of supraoccipital crest hypertrophic, Fig. 2 View FIGURE 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 View FIGURE 2 A- 5; vs. anteriorly convex, with a medial suture, Fig. 2 View FIGURE 2 E- 5), and the anterodorsal surface of the ethmoid large and strongly bifurcate ( Fig. 2 View FIGURE 2 A- 8; vs. large, non-bifurcate, Fig. 2 View FIGURE 2 E- 8).

Cheimerius matsubarai is discernible from Argyrops in having many small blue spots, some pairs slightly overlapping, dorsolaterally on the body ( Figs. 3 A View FIGURE 3 A , 4 View FIGURE 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 View FIGURE 2 A- 5; vs. protuberant and medially robust without pores in Argyrops , Fig. 2 View FIGURE 2 C- 5) and ethmoid conditions ( Fig. 2 View FIGURE 2 A- 8; vs. large and non-bifurcate in Argyrops , Fig. 2 View FIGURE 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 View FIGURE 6 ).