Schismatogobius baitabag, 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 : 59-60

Schismatogobius baitabag , new species

( Figs 2C , 4 , 8 ; Tabs I-III)

Material examined. – Three specimens from Papua New Guinea with a size range of 22.5-27.8 mm SL .

Holotype. – NTM S13675-011 , male (27.8 mm SL); Baitabag Village, Nagada River , Madang, Papua New Guinea, 13 Oct. 1992, coll. Larson, Mizeu, Matthew and villagers.

Paratypes. – NTM S13675-001 , 1 female (25.9 mm SL); same data as holotype . WAM P29613-015 , 1 female (22.5 mm SL); Bogia, 4.5 N road to Awar, 19 Oct. 1987, coll. Allen and Parenti.

Diagnosis

Usually 15 pectoral rays; pectoral fins banded with rows of dark spots. Membrane in first dorsal fin posterior to spine 6 partly connected to base of spine of second dorsal fin. Ventral surface of head, frenum and pelvic disk in male yellowish, with black mentum and lower lips. Ventral surface of head, frenum and pelvic disk in female yellowish, with dark mentum.

Description

A medium sized Schismatogobius (average size 25 mm SL). Body naked, slender, almost circular in cross-section. Head rounded, snout rather rounded. Mouth oblique, tip of lower lip anteriormost. Jaw lengths in male much greater than in females; 54% in male holotype (in HL), 26-31% in females. Lower jaw reaching a vertical of anterior third of eye in female and reaching (for 1/4 of eye diameter) a vertical of posterior part of eye in male. Eyes high on head, close together with interorbital width about one third of the eye diameter. Anterior nostril in short tube.

Dorsal fins VI-I,9, membrane of first dorsal fin posterior to spine 6 partly connected to base of spine of second dorsal fin. D1 with all spines about equal in length. D2 depth low, base long. Anal fin I,9, slightly behind or approximately below second dorsal fin origin. Caudal fin with 11-13 branched rays, posterior margin rounded. Pectoral fins oblong with posterior margin pointed and 14(1)-15(2) rays ( Tab. I), ventralmost ray unbranched. Pelvic fins always I,5, with both fins joined together their entire length between rays 5, forming strong cup-like disc; a well developed frenum between spines, fin not extending beyond anus. Morphomeristics data given in table III.

Tongue (anterior tip) bilobed. Teeth in upper jaw (14- 18) usually in two or three rows, teeth conical and slightly recurved. Teeth in lower jaw (10-12) 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 not well developed and inconspicuous due to preservation.

Sexual dimorphism fairly well developed with male having jaws longer than female. Urogenital papilla broadly rounded in females and slightly triangular in male.

Colour in preservation ( Fig. 8 )

Usually four vertical brown bands in dorsal view; first band below first dorsal fin, second and third bands below second dorsal fin and fourth band at base of caudal fin. Body and nape otherwise pale fawn with vermiculate brown markings and spots. Head beige with fine brownish speckling. Ventral surface of head, frenum and pelvic disk in male yellowish, with dark mentum and dark brown lower lip. Ventral surface of head, frenum and pelvic disk in female yellowish with dark mentum ( Fig. 2C ). Belly whitish; breast whitish. First and second dorsal fin mostly cream with rows of black spots. Caudal fin striped and translucent, with small dark brown spot at hypural crease. Anal fin mostly cream. Pectoral fins banded with rows of small dark spots.

Colour in life

Field notes by HKL on live holotype: “Generally yellowish brown with faint orange mouth. Live colour – translucent colours; pale honey brown with four brown bands across body (last across base of tail). Row of irregular brown markings along midside of body. Dorsal half of body has tiny whitish spots scattered evenly over the pale honey-gold brown. A fifth brownish – very indistinct – band runs just behind pectoral fin to D1 origin – with two small brown spots in dorsal midline in centre of band. Brown mark from eye to middle of mouth. Dorsal fins with fine brown spots.” On a very poor colour slide of the holotype (taken while alive, viewed from above), it can be seen that the head and body are yellowish brown with dark brown body bands and fine whitish spots cover the nape and dorsum. The iris is reddishgold. The pectoral fin is transparent with rows of small dark spots interspersed with at least two rows of whitish spots.

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 8. – Schismatogobius S. baitabag n. sp., holotype, NTM S13675-011, male, 27.8 mm SL (Photo P. Keith).