Schismatogobius alleni, Keith & Lord & Larson, 2017

Keith, Philippe, Lord, Clara & Larson, Helen K., 2017, Review of Schismatogobius (Gobiidae) from Papua New Guinea to Samoa, with description of seven new species, Cybium 41 (1), pp. 45-66 : 62-63

Schismatogobius alleni , new species

( Figs 2E , 4 , 10-11 ; Tabs I-III)

Material examined. – Two specimens from Papua New Guinea with a size range of 27.6-33.3 mm SL .

Holotype. – QM I.39304, female (33.3 mm SL); Uruf Creek , tributary of Markham River, Papua New Guinea, 3 Jul. 2012, coll. Webb.

Paratype. – AUM 47579 , male (27.6 mm SL); Ularimbin creek , East Sepik, Papua New Guinea, 7 Oct. 2007, coll. Armbruster et al .

Diagnosis

17 pectoral rays; pectoral fins banded. Membrane in first dorsal fin posterior to spine 6 not connected to base of spine of second dorsal fin. Transverse row of papillae on mid-cheek between row b and d. Ventral surface of head in male plain brownish with blackish pigment on frenum and pelvic disk. Ventral surface of head in female blackish, black pigment surrounding whitish mentum and middle of lower lip; frenum whitish.

Description

A medium sized Schismatogobius (average size <30 mm SL). Body naked, slender, rounded anteriorly, compressed posteriorly. Head bluntly rounded, snout obtuse, cheeks bulbous. Mouth oblique, tip of lower lip anteriormost. Jaw lengths in males much greater than in females. Lower jaw reaching a vertical from posterior part of eye in female and exceeding (for 1/2 of eye diameter) a vertical of posterior part of eye in male. Eyes high on head, close together with interorbital width of 15% of HL in female. Anterior nostril in short tube.

Dorsal fins VI-I,9, membrane in first dorsal fin posterior to spine 6 not connected to base of spine of second dorsal fin. D1 with all rays about equal in length. Anal fin I,9, slightly behind or approximately below second dorsal fin. Caudal fin with 10-12 branched rays, posterior margin rounded. Pectoral fins oblong with posterior margin pointed and 17 rays ( Tab. I), ventralmost ray unbranched. Pelvic fins always I,5, with both fins joined together for their entire length between rays 5 to form strong cup-like disc, a well developed lobed frenum between spines; fins not reaching anus. Morphomeristics data given in table III.

Tongue (anterior tip) bilobed in male; reduced and round- ed in female. Teeth in upper jaw (20-22) usually in two rows, teeth conical and slightly recurved, usually. Teeth in lower jaw (11-12) in one or two rows of teeth anteriorly and single row laterally, all teeth conical with outer row teeth only slightly enlarged and somewhat recurved.

Cephalic sensory pore system always with pores B, D, F, K, L, N and O, pore D singular with all other pores paired; oculoscapular canal absent between pores F and K. Anterior interorbital extension of anterior oculoscapular canal with double terminal pores B slightly posterior to posterior nostril. D pore at rear of interorbital. Posterior extension of anterior oculoscapular canal terminating laterally on each side of head at pore F, just behind posterior edge of eye. Posterior oculoscapular canal with 2 terminal pores, K and L; preopercular canal with 2 pores, N and O. Cutaneous sensory papillae with a distinct supplementary transverse row of papillae on the cheek between row b and d ( Fig. 11 ).

Sexual dimorphism fairly well developed with male having jaws longer than female and different colour pattern on ventral surface of head. Urogenital papilla broadly rounded in females and slightly triangular in males.

Colour in preservation ( Fig. 10 )

Head and body dark grey dorsally and whitish ventrally with three dark brown bands, first band below first dorsal fin, second below second dorsal fin and third band below rear of second dorsal fin; bands reaching to mid-side of body where they become staggered dark blotches and oblique dark lines. Dorsal half of body with indistinct whitish spots. Ventral surface of head in male entirely blackish with blackish pigments on frenum and pelvic disk ( Fig. 2E ). Ventral surface of head in female entirely blackish, black pigment surrounding whitish mentum and middle of lower lip. Pelvic frenum whitish ( Fig. 2E ); breast and belly whitish. First dorsal fin whitish with 2-3 rows of dusky spots and narrow dusky margin; in male, fin has broad black band. Second dorsal fin transparent to whitish with 3-4 oblique rows of small dark spots. Anal fin translucent whitish with dusky streaks posteriorly. Pectoral fins with plain dusky area basally, rest of fin translucent whitish with two broad rows of blackish spots (forming two blackish bands that are broad dorsally and narrow ventrally) and a third fainter row of spots toward tip of fin. Pelvic fins translucent whitish. Caudal fin whitish, with large blackish angular blotch extending from base onto fin, oblique blackish lines extending out from blotch forming large X; on either side of posteriormost part of blotch, two rows of small blackish spots on remainder of fin.

Colour in life

Unknown, but probably similar to that in preservation, with bright reddish or rose colour between black transverse bands.

Figures

Figure 2. – A-F: Schematic drawings of the ventral surface of head of Schis- matogobius species from Papua New Guinea to Samoa. A: 13-14 pectoral rays.

Figure 4. – Distribution area of Schismatogobius species from Papua New Guinea to Samoa.

Figure 10. – Schismatogobius alleni n. sp., holotype, QM I.39304, female, 33.3 mm SL (Photo P. Keith).

Figure 11. – Diagrammatic illustration of head in Schismatogobius alleni showing cephalic sensory pore system and cutaneous sensory papillae. A: Dorsal view; B: Lateral view.