Last update: 13 May 2017

Common names:

* proposed name

Synonyms:

Etymology:
'Oxuderces' comes from the Greek 'oxuderkês' (quick-sighted), which probably refers to the quick burying behaviour, elicited by visual stimuli

'dentatus' means 'toothed' in Latin, which refers to the large canines of the upper jaw

Maximum recorded length:
94 mm SL (Jaafar and Parenti, 2016)

Live colouration (Jaafar & Parenti, 2016; see main photo and drawing B):
ground colour of dorsum and flanks greyish blue to greenish-brown, ventrally whitish to dusky; D1 translucent; D2 transparent except for a faint dusky medial stripe and a black blotch with distal orange margin, near distal tips of last 3 rays; caudal fin dusky; anal fin yellowish and partially transparent, pectoral and pelvic fins translucent to dusky; upper lip and tips of anterior nostrils lined with black

Colouration on preservation (Jaafar & Parenti, 2016; see photos A, B):
ground colour slate grey to light brown; Herre (1927) reported 7-8 brown dorsal cross bands posteriorly on flanks, in his smallest specimens (41 mm; see drawing D); all fins hyaline except for the dark gray to dark brown blotch at the posterior tip of D2; tips of anterior nostrils and upper lip lined with black to dark brown

Diagnosis (Jaafar & Parenti, 2016):
first hemal spine extending ventrally to mid-length of the first anal-fin pterygiophore (versus extending ventrally to a point dorsal to mid-length of the first anal-fin pterygiophore in O. nexipinnis); no conspicuous dermal invagination posterior to the point of attachment of pelvic-fin base; mouth terminal; head length 25-28%SL.

The genus is diagnosed by (1) a fleshy external trough (deep groove or slit) running along the medial longitudinal axis in a dorsal interorbital position (see photo G of O. nexipinnis); the groove is supported internally by two ridges of the medially fused frontal bones (interorbital bridge) that curve towards the midline, and is lined with thick epidermis and thin dermis; (2) highly thickened epidermis over the eye; (3) neural spine of the fourth vertebra broad, spatulate and posteriorly directed; (4) portion of the anterior ceratohyal posterior to the insertion of the fourth branchiostegal ray elongate and notched (versus not elongate, or elongate and not notched; see drawing F); and (5) the metapterygoid-symplectic-quadrate strut and the anguloarticular form an acute angle

Description (Jaafar & Parenti, 2016):
Head wider than deep: head length (HL) 25-28%SL, head width 36-48%HL, head depth 32-42%HL. Eye diameter 9-14%HL; interorbital distance 4-5%HL. Snout length 13-17%HL, jaw length 45-57%HL. Body depth at anus 11-12%SL, body width at anus 5-7%SL. Predorsal length 29-37%SL. Length of base of D1 plus D2 58-60%SL; length of base of anal fin 36-43%SL; pelvic-fin length 14-18%SL; pectoral-fin length 15-19%SL; caudal-fin length 20-25%SL. D2 with 25-27 elements; anal fin with 24-26 elements; pectoral rays 22-23. Lateral longitudinal scale count 51-59; predorsal midline with 0-29 scales: in some specimens the ventral region of head, isthmus, dorsal region anterior to D1 and pectoral-fin bases are scaleless; scales on body increasing in size posteriorly.

All congeners also have: depressed anterior portion of the head and pointed snout profile. Distinct notch in middle of upper lip between two medial premaxillary teeth; thick lips, with posterior lip distally protruding. Gape wide, extending 3-4 eye lengths posterior to the orbit; preopercle thin and crescent-shaped, five thin branchiostegal rays. Roof of mouth with fleshy ellyptical palp with pointed tips, studded with papillae. Oral jaw teeth in single row both on premaxilla and dentary, all caninoid; premaxillary teeth decreasing in length posteriorly, dentary teeth more uniform in size; 1-2 canine teeth on both sides of premaxillary symphysis, longer than other teeth, extending anteroventrally and projecting beyond lower jaw when mouth closed; no canine teeth on both sides of mandibular symphysis; no vomerine and palatine teeth. Gill opening restricted, beginning from a point anterior to midpoint of pectoral-fin base, then coursing anteroventrally to a point dorsal to the pelvic fin origin. Eyes not meeting medially, without dermal cup. Supraorbital pore C in the anterior portion of the fleshy external interorbital trough; anterior oculoscapular pores; large posterior nostril, anteroventral to eye; anterior nostril at tip of pendulous short tube overlapping lower jaw. D1 and D2 connected by membrane for entire height; D2 or anal fin and caudal fin not connected by membrane; D1 with six spines; all elements of D2 and anal-fin segmented rays, last two rays sharing same pterygiophore; pelvic fins fused in a pelvic disc, not reaching genital papilla; caudal fin lanceolate with 17 segmented rays; dorsal procurrent rays 5; ventral procurrent rays 4; 2 epural bones. Male genital papilla triangular and conical, with posterior tip pointed; female genital papilla rectangular and bulbous

Diet:
no published study is available

Reproduction:
no published study is available

Ecological notes:
The ecology of this species is poorly known. Previous accounts may refer to the congener O. nexipinnis

Distribution:
coastal China, from Shanghai south to Macao; type locality: Macao; the holotype may have been collected in Guandong, China (Murdy, 1989; Jaafar & Parenti, 2016)

Remarks:
Oxuderces is the type genus of the subfamily Oxudercinae (Murdy, 1989). Both the the type's figure and the original description of the monotypic Apocryptichthys Day, 1876, that Day erected for Apocryptes cantoris Day, 1871 (Day 1876), conform to Oxuderces (Springer, 1978; Murdy, 1989; Jaafar & Parenti, 2016). However, the original description of Apocryptes cantoris Day, 1871 (probably BMNH 1870.5.18.23) conforms to a species of Scartelaos (sensu Murdy, 1989; Kottelat, 2013; and Jaafar & Parenti, 2016). See Springer (1978) for further details. Therefore, Jaafar & Parenti (2016) considered Apocryptichthys to only partly include members of Oxuderces, and reviewed the taxonomic and nomenclatural implications. The holotype of O. dentatus (MNHN A.1822) is a malformed specimen without pelvic fins (Jaafar & Parenti, 2016). The date of the original description of O. dentatus published here follows Murdy (1989) and Jaafar & Parenti (2016)

Photographs of Oxuderces dentatus:

A: formalin-fixed specimen (SYSZ 0030053; Qi'ao Cun market, Qi'ao Island, Zhuhai, Guangdong, China; photo courtesy of Ronfeng Ray Cui, 2005), B: detail of head (same locality of A; photo courtesy of Ronfeng Ray Cui, 2005)

Drawings of Oxuderces dentatus:

A F

B C

D E

A: cephalic sensory and nasal pores of Oxuderces spp.: an = anterior nostril; ao = anterior oculoscapular canal pore; f = caninoid teeth; pio = posterior interorbital pore C; pn = posterior nostril (modified from Murdy, 1989)*; B: illustration of the holotype of Oxuderces dentatus Eydoux & Souleyet, 1848 (Eydoux & Souleyet, 1850); C: Apocryptichthys pellegrini Wu (Wu, 1931); D: Apocryptichthys sericus Herre (Herre, 1927); E: Apocryptichthys sericus Herre (Pan et al., 1991); F: lateral view of the hyoid arch of Ox. dentatus, rotated about 45° clockwise; the portion of the anterior ceratohyal that has a different shape in other oxudercine genera is coloured in red: Ch = ceratohyal; an = anterior ceratohyal; po = posterior ceratohyal; 1-5 = branchiostegal rays (modified from Murdy, 1989)* - * with permission