Oxuderces, DENTATUS EYDOUX & SOULEYET, 1848

Jaafar, Zeehan & Parenti, Lynne R., 2017, Systematics of the mudskipper genus Oxuderces Eydoux & Souleyet 1848 (Teleostei: Gobiidae: Oxudercinae) with resurrection from synonymy of O. nexipinnis (Cantor 1849), Zoological Journal of the Linnean Society 180 (5), pp. 195-215 : 206-207

OXUDERCES DENTATUS EYDOUX & SOULEYET, 1848

FIGURES 1 , 3A , 10A , 11 , AND 12; TABLE 1

Oxuderces dentatus Eydoux & Souleyet, 1848: 182 (type locality, Kwantung , near Macao, China)

Apocryptichthys sericus Herre, 1927: 264 (type locality, Amoy , China)

Apocryptes pellegrini Wu, 1931: 48 (type locality, Foochow , China)

Holotype (examined): MNHN A-1822, female, 77.5 mm SL, 91.0 mm TL, Kwantung, near Macao, China, by La Bonite, 1837.

Other material examined: Eight specimens, 54.3 – 93.8 mm SL: CAS-SU 25524 , female (65.0 mm), Xiamen , China ; CAS-SU 61139 , male (75.3 mm), Macao, China ; USNM 85846 , male (80.3 mm), female (80.2 mm), Fengsien , Nanking (near Shanghai), China ; USNM 86378 , 2 females (54.3 – 67.3 mm), Foochow and nearby Fukien, China ; USNM 86954 , male (78.7 mm), 1 undet. (C&S, 93.8 mm), Foochow , Fujian, China .

Differential diagnosis: Oxuderces dentatus is differentiated from its sole congener O. nexipinnis in having: first hemal spine extending ventrally to a point approximately mid-length of first anal-fin pterygiophore (vs. terminating dorsal to mid-length of first anal-fin pterygiophore; see Fig. 10 ); mouth terminal (vs. superior); no conspicuous dermal invagination posterior to point of attachment of pelvic-fin base (vs. present); and head relatively short (25.1 – 27.7%SL vs. 27.3 – 30.3%SL).

Description: Head markedly depressed, wider than deep, head length 25.1 – 27.7%SL, head width 35.8 – 48.1%HL, head depth 32.4 – 42.5%HL. Eye diameter 8.7 – 13.7%HL; interorbital narrow, interorbital distance 3.7 – 5.4%HL, eye without dermal cup. Snout profile broadly pointed, snout length 12.8 – 17.5%HL. Mouth terminal; gape wide; jaw length 44.6 – 57.1% HL; distinct notch in middle of upper lip between two medial teeth. Teeth in premaxilla and dentary caninoid, unevenly spaced, in single row; one or two prominent and elongate canine tooth/teeth on each side of premaxillary symphysis, canine teeth on premaxilla extending anteroventrally beyond lower jaw when mouth closed, teeth decreasing in length posteriorly; teeth in dentary more uniform in size, all teeth shorter than medial canine teeth of premaxilla, teeth absent posteriorly, no canine tooth on each side of symphysis internal to anterior margin of dentary. Body compressed and stout, body depth at anus 10.7 – 12.5%SL, body width at anus 5.2 – 6.9%SL. Predorsal long, predorsal length 28.7 – 36.8%SL. D1 and D2 connected by membrane for entire height, base of D1 and D2 57.6 – 59.8%SL; base of anal fin 36.4 – 42.8%SL. No membrane connecting D2 or A to caudal fin. Pelvic fin rounded, not reaching genital papilla, pelvic-fin length 14.4 – 18.4% SL. Pectoral-fin length 14.6 – 18.8%SL. Caudal fin long, lanceolate, 20.5 – 25.4%SL. First dorsal fin (D1) with six spinous rays ( VI); all elements of D2 and A fins segmented, D2 with 25 – 27 elements, A fin with 24 – 26 elements; pectoral rays 22 – 23; caudal fin segmented rays 17; dorsal procurrent rays 5, ventral procurrent rays 4. Two epural bones. Lateral longitudinal scale count 51 – 59. Predorsal midline with 0 – 29 scales, scales may be small and embedded in skin. In specimens without predorsal scales, entire dorsal region anterior to D1 as well as the isthmus, pectoral-fin base and ventral region of head without scales; scales on body small and embedded in skin anteriorly, and increasing in size posteriorly. Raised free-neuromast rows on head.

Coloration: Eydoux & Souleyet (1848:183) described the colour of the holotype: ‘Ce poisson est d’un brun verdâtre supérieurement et sur les côtés; inférieurement, il est d’une couleur blanchâtre. Les nageoires sont grisâtres [This fish is greenish-brown on the dorsal surface and on the sides; on the ventral surface, it is whitish. The fins are grayish]’. Wu (1931) reported live specimens with a bluish throat and abdomen and a black line on the upper lip. Preserved specimens are uniformly light brown with a dark brown to black upper lip and pectoral-fin base. There is a diffuse, dark brown spot at half of ray height, on the posterior distal end of D2; the spot lies between the 20 th and the penultimate rays. Eydoux & Souleyet (1848) did not mention nor did they illustrate the spot, although Springer (1978) reported it in examination of the holotype. Only Herre (1927: 265 – 266) reported the presence of seven to eight brown dorsal cross bands posteriorly in his smallest specimen (41.0 mm).

Etymology: Latin, ‘ dentatus ’ meaning ‘toothed’, in reference to prominent canines on the upper jaw.

Distribution and ecological note: Known from isolated localities in coastal China, from Shanghai south to Macao ( Fig. 13 ). Ecology poorly known; reports on the natural history of O. dentatus may refer to O. nexipinnis .

Remarks: Data associated with the holotype indicate that it was collected from Kwantung (Guangdong), China, the province adjacent to Macao, although all other reports identify the type locality as Macao. The precise locality of collection of the holotype is probably unknowable. The holotype is in poor condition, with most teeth lost and pelvic fins abnormally absent ( Figs 11 , 12A ). Various dates have been cited for the description of O. dentatus : 1842 in Springer (1978), or 1848 in Murdy (1989). In an attempt to standardize the dates of publication, Bauchot et al. (1982) inadvertently introduced more confusion. In the abstract presented in English, the authors wrote that fishes described by Eydoux & Souleyet were ‘...published as late as 1850’ ( Bauchot et al., 1982: 59). In the abstract presented in French, they wrote ‘La publication est postérieure à 1848 et peut avoir été aussi tardive que 1850 [The publication was made after 1848, and may have been

as late as 1850]’ ( Bauchot et al., 1982: 59). Elsewhere in the paper, and in English, they concluded that the volume describing fishes from the voyage ‘...were published after March 1848 ’ ( Bauchot et al., 1982: 63). We use 1848 following Murdy (1989) and the earliest year within the range proposed by Bauchot et al. (1982).

Figures

Figure 1. Illustration of the holotype of Oxuderces dentatus Eydoux & Souleyet (1848: pl. 8, fig. 3) from the original description. Image courtesy of the Smithsonian Institution Libraries.

Figure 3. Dorsal view of the head including interorbital region of (A) Oxuderces dentatus (ZRC 53939) and (B) Oxuderces nexipinnis (ZRC 53919). Arrow points to interorbital trough or groove. A sensory pore C sits in the anterior portion of the trough. C, Apocryptodon wirzi (AMS I23993.007), there is a single sensory pore D, and no trough; D, Apocryptodon glyphisodon (USNM 99874), there is a paired sensory pore E and no trough. Scale bar = 3 mm.

Figure 10. Line drawings of the last precaudal and the first two caudal vertebrae and associated elements of the anal fin in (A) Oxuderces dentatus (USNM 86954) and (B) Oxuderces nexipinnis (USNM 279359). In O. dentatus, the hemal spine extends to a point at about mid-length of the first anal-fin pterygiophore; in O. nexipinnis the hemal spine terminates closer to the proximal tip of the first anal-fin pterygiophore. Bone is stippled; cartilage is represented by open circles.

Figure 11. Holotype of Oxuderces dentatus Eydoux & Souleyet (1848), MNHN A.1822, 77.5 mm SL.

Figure 12. Oxuderces dentatus, head and anterior portion of the body in ventral view. A, MNHN A.1822 (holotype, 77.5 mm SL) has pectoral fins and lacks pelvic fins. B, USNM 85846 (80.3 mm SL) has fully formed pectoral and pelvic fins. The arrow in A points to the area where the pelvic fins have either been lost or never developed. Anterior is to the left.

Figure 13. Distribution map of Oxuderces dentatus (solid circles) and Oxuderces nexipinnis (solid triangles). Each symbol represents one catalogued museum lot. Distributional limits are approximated by a solid line.