Atractoscion microlepis, Song & Kim & Kang & Kim, 2017

Song, Young Sun, Kim, Jin-Koo, Kang, Jung-Ha & Kim, Seong Yong, 2017, Two new species of the genus Atractoscion, and resurrection of the species Atractoscion atelodus (Günther 1867) (Perciformes: Sciaenidae), Zootaxa 4306 (2), pp. 223-237 : 231-234

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Atractoscion microlepis

sp. nov.

Atractoscion microlepis sp. nov., Song, Kim & Kang

English name: Small scale lunate caudal fin croaker; Korean name: Jan-bi-neul-cho-seung-kko-ri-min-eo ( Figs. 1–2 View FIGURE 1 View FIGURE 2 , Tables 2–3)

Atractosion aequidens (not of Cuvier, 1830): Jaward et al., 2012: 13, OMMSFC 1087, 671.0 mm SL, caught by fisherman using a deep gill net off the city of Salalah, Southern Oman, Arabian Sea, 7 June 2011.

Holotype. PKU 9315, 280.0 mm SL, Gulf of Oman, caught by local fishermen, July 2013.

Paratypes. PKU 9312–9314, 9316, 279.4–355.0 mm SL, Gulf of Oman, caught by local fishermen, July 2013 ; PKU10774 View Materials –10783, 269.0–340.0 mm SL, Gulf of Oman, caught by local fishermen, July 2014 .

Diagnosis. Dorsal fin soft rays, 25–26 (26); pored lateral line pored scales, 76–82 (78); body depth 20.0– 27.3% of SL; head depth 17.7–20.1% of SL; teeth cardiform or pluriserial; margin of caudal fin emarginate; swim bladder with an anterior pair of horn-like appendages; distributed in Omani region of Arabian Sea.

Description. D. X–XI, 25–26 (26); A. II. 9; P1. 18; P 2. I, 5; C. 9 + 5; LLp. 76–82 (78); Vertebrae 24–25; GR. 5 + 1 + 8. The counts and measurements for 15 specimens are given in Tables 2 and 3. Largest examined specimen was 355.0 mm SL. Overall view of body is shown in Figure 2 View FIGURE 2 .

Body large, moderately compressed, relatively deep and tapering slightly toward tail; head large; eye large, interorbital region depressed. Two pairs of nostrils anterior to eyes; anterior nostrils circular, posterior nostrils an elongated ellipse; anterior nostril smaller than posterior. Snout acutely pointed; mouth large, terminal, strongly oblique; upper jaw shorter than lower jaw; upper jaw extending backward below posterior margin of eye, or a little behind; teeth on both jaws depressible and well-developed, without large canine-like teeth; 3–4 irregular rows of cardiform or pluriserial teeth; outer teeth larger than inner on upper jaw, equal in size on lower jaw; teeth on vomer and palatines absent. Barbels and sensory pores on lower jaw absent. Operculum large, broad; margin of opercle with two spines covered by membrane. Gill rakers short, dentate, 5 on upper limb, 8–9 on lower limb of first gill arch. Origin of dorsal fin above behind origin of pectoral fin; dorsal fin with X–XI slender spiny-rayed regions, followed by deep notch, and 25–26 soft rays, spines higher than soft rays. Posterior of dorsal-fin base posterior to base of anal fin. Pectoral fin small, pointed, its tip extending below 7th–8th dorsal-fin spine. Origin of pelvic fin slightly behind origin of pectoral fin, fin with an axillary scale. Origin of anal fin below and between 18th and 19th dorsal-fin soft rays. Caudal fin emarginate to lunate, upper lobe longer than lower. Lateral line from above operculum to margin of caudal fin; lateral line pored scales very small, 76–82 (mode 78). Anus closer to origin of anal fin than to origin of pelvic fin. Body covered with scales except for preorbital region; body scales small, ctenoid (rough), head scales cycloid (smooth). Swim bladder well developed with thick wall; carrot-shaped with an anterior pair of horn-like appendages, not entering head. Sagittal otoliths thick, large with a tadpole-shaped impression; sulcus head of otolith broad, tail short, J-shaped.

Colouration when fresh: dorsal surface of body dark grey; head silvery-white; head from orbital region to nape blackish; upper and lower jaw tips blackish; margin of maxilla pale dark; around eyes dark red and/or brown; dorsal and pelvic fins mostly clear or hyaline; dorsal-fin soft rays and anal fin pale yellow, its bases light red; pectoral-fin base spot dark brown; caudal fin dark yellow with blackish its margin.

Colouration when fixed: dorsal surface of body dark brown, ventral surface silvery-white; snout tip blackish; around nostrils dark; dorsal and caudal fin margins blackish; pectoral-fin filament pale, its base dark brown; lateral line scales white.

Geographic distribution. Gulf of Oman, Arabian Sea.

Etymology. The specific name, microlepis , refers to the small scales.

Comparisons. The 15 specimens were very similar to two congeneric species, but in some characteristics were clearly differentiated. Morphologically, A. microlepis sp. nov. is clearly distinguished from A. aequidens by the mode number of lateral line pored scales (78 for A. microlepis sp. nov., 76 for A. aequidens ) and from A. nobilis by the number of dorsal-fin soft rays (25–26 for A. microlepis sp. nov., 20–23 for A. nobilis ) ( Figs 1–2 View FIGURE 1 View FIGURE 2 , Table 3). A. microlepis sp. nov. differs from A. aequidens and A. nobilis in the body depth as a percentage of the SL (20.0– 27.3% for A. microlepis sp. nov., 19.4–22.4% for A. aequidens , 23.8–26.1% for A. nobilis ), the head depth as a percentage of the SL (17.7–20.1%, 15.7–17.5% and 18.6–18.9%, respectively), the pectoral-fin length as a percentage of the SL (14.9–17.4%, 12.4–15.5% and 19.9–21.5%, respectively), and the snout length as a percentage of the head length (23.9–28.7%, 25.1–30.1% and 18.1–22.5%, respectively) (Table 2). The original description of A. aequidens gave no description of the lateral line pored scales ( Cuvier 1830). Sasaki (1996) provided a simple record of A. aequidens from the Gulf of Aden. According to Jawad et al. (2012), the first record of A. aequidens from Oman was based on a single specimen. Reference to the study of Jawad et al. (2012) shows that there are no meristic or quantitative morphological differences between A. microlepis sp. nov. and A. aequidens , and in the present study they are considered to be the same species. To clarify the taxonomic status of A. microlepis sp. nov. we compared 506 bp sequences of mtDNA COI from A. microlepis sp. nov. with those of other Atractoscion species. The neighbour joining tree showed that, based on K2P distances, the specimens of A. microlepis sp. nov. differed from A. aequidens by 4.8–5.0%, and from A. nobilis by 8.6–11.2% ( Fig. 3 View FIGURE 3 , Table 4).

(1) (2) (3) (4) (5) (6)

Atractoscion aequidens (1) South Africa

Atractoscion nobilis (2) California 0.089

Atractoscion atelodus (3) Australia 0.052 0.101

Atractoscion macrolepis Angola and Namibia 0.044 0.086 0.056 sp. nov. (4)

Atractoscion microlepis Oman 0.048 0.110 0.036 0.061 sp. nov. (5)

Miichthys miiuy (6) – 0.161 0.159 0.151 0.163 0.158 Larimichthys polyactis (7) – 0.229 0.222 0.239 0.221 0.238 0.211


University of Coimbra Botany Department