Gymnoamblyopus novaeguineae, Edward O. Murdy & Carl J. Ferraris, Jr., 2003

Edward O. Murdy & Carl J. Ferraris, Jr., 2003, Gymnoamblyopus novaeguineae, a new genus and species of worm goby from Papua New Guinea (Gobiidae: Amblyopinae)., Zootaxa 150, pp. 1-6 : 2-5

Gymnoamblyopus novaeguineae , new species

(Fig. 1; Table 1)

Taenioides sp.: Allen 1991:202-203, photo 31.

Holotype: WAM P.29823-001 , 99.0 mm SL, female, collected by K. Hortle and A. Maie, 30 July 1987, in the Lower Fly River , Papua New Guinea (8°10’S, 142°10’E) .

Diagnosis. As for genus.

Description. Total dorsal-fin elements 33; first and second dorsal fins continuous; first dorsal fin with six flexible spines; all rays of second dorsal fin segmented and branched; dorsal-fin base long and broadly joined with caudal fin. Total anal-fin rays 26, all segmented and branched; anal-fin height approximately equal to second dorsal-fin height; anal-fin membrane broadly joined with caudal fin. Membrane of dorsal and anal fins thick and rubbery. Pectoral fin with 16 rays, fin margin rounded posteriorly, pectoral-fin length 59% of pelvic-fin length; all pectoral-fin rays segmented and most are branched. Pelvicfin rays I, 5, with well developed frenum and connecting membrane forming cup-shaped disc. Caudal fin slightly longer than head, representing about 16% of total length.

Head depressed with a slightly compressed body. Scales absent from head and body.

Teeth on outermost row of jaws enlarged, sharp and pointed; when mouth closed, outermost teeth interlock. Upper and lower jaws with 2 rows of teeth posterolaterally and 3-4 rows anteromedially. No caninoid teeth internal to symphysis of lower jaw. Outer-row teeth larger than inner row(s); outer row teeth of lower jaw longer than those of upper-jaw; 11 teeth in outer row of upper jaw; 6 teeth in outer row of lower jaw. No palatine or vomerine teeth present.

Mouth large and vertical. Lips fleshy especially at rictus.

Eye rudimentary, but distinct; covered by skin. Posterior naris lateral to, and slightly anterior to, eye. Anterior naris at tip of small flap of skin overhanging upper jaw.

Cephalic sensory canals and pores absent. Mandibular papillae pronounced, other sensory papillae on head difficult to discern. No raised dermal folds or ridges on head. No barbels on ventral surface of head.

Spinous dorsal-fin pterygiophore formula 3-12210. Precaudal vertebrae 10, caudal vertebrae 16. Single anal-fin pterygiophore anterior to first hemal spine. Pleural ribs short and posteriorly directed.

Measurements are provided in Table 1. Selected proportional measurements are as follows: SL/TL = 0.843; HL/SL = 0.199; PEL/SL = 0.131; PEL/HL = 0.660; PEC/SL = 0.077; PEC/HL = 0.386; PEC/PEL = 0.585; head width/SL = 0.148; snout length/SL = 0.052; jaw length/SL = 0.063; interorbital width/SL = 0.041; nape width/SL = 0.118; body depth/SL = 0.102; predorsal length/SL = 0.301; prepelvic length/SL = 0.246; and preanal length/SL = 0.573.

Coloration. Based on a color photograph in Allen (1991) of the holotype and only specimen after it had been preserved, anteriorly yellowish brown grading to tannish brown posteriorly. Whitish on the ventral portion of opercle. No markings, bars, or spots on head or body.

Distribution. Type and only known locality is the Lower Fly River, Papua New Guinea. Holotype was collected near Burei Junction approximately 200 km upstream from the Fly River mouth (Allen, 1991). According to Allen (1991), the water in this part of the river is tidally influenced but fresh.

Etymology. The specific name, novaeguineae, refers to the type locality of this species, the island of New Guinea and is treated as a noun in apposition.

Comparison of Gymnoamblyopus with other “Taenioides” group genera. Gymnoamblyopus is the only member of the “Taenioides” group with a single anal-fin pterygiophore anterior to the first hemal spine; all others have at least two. Gymnoamblyopus differs from all “Taenioides” group members, except Taenioides , in being devoid of scales.

Gymnoamblyopus differs from Taenioides in not possessing barbels on the underside of the head, and in lacking raised dermal folds or ridges on the head and body. Gymnoamblyopus also lacks the Y-shaped, second anal-fin pterygiophore of Taenioides .

Gymnoamblyopus differs from Pseudotrypauchen in having a depressed head and subcylindrical body (vs. head and body compressed in Pseudotrypauchen ), and in having short and rounded pectoral fins (vs. long and pointed in Pseudotrypauchen ).

Gymnoamblyopus lacks symphysial canine teeth, which are present in Odontamblyopus , and has short rounded pectoral fins with branched rays, rather than large rounded pectoral fins with free rays.

Gymnoamblyopus differs from Brachyamblyopus in having a vertical mouth (vs. oblique in Brachyamblyopus ) and short, posteriorly-directed pleural ribs (vs. well-developed, ventroposteriorally-directed pleural ribs in Brachyamblyopus ).

Key to the genera of the “Taenioides” group

(modified from Larson and Murdy, 2002)

1a. Head and body naked .................................................................................................... 2

1b. Cycloid scales on head and body (sometimes difficult to discern without magnification) ....................................................................................................................................... 3

2a. Head and body with raised dermal folds or ridges; ventral surface of lower jaw usually with three pairs of long, fleshy barbels .......................................................... Taenioides

2b. Head without distinct raised dermal folds or ridges; head without barbels .................... ......................................................................................... Gymnoamblyopus , new genus

3a. Most pectoral-fin rays simple, free from fin membrane; pectoral-fin rays 20-65, usually more than 23 ........................................................................................................... 4

3b. Most pectoral-fin rays branched, not forming free rays; pectoral-fin rays 23 or fewer.. ............................................................................................................ Brachyamblyopus

4a. Head and body subcylindrical (slightly compressed posteriorly), greatly elongate, body depth less than 10% of SL; teeth in outermost row of jaws enlarged, fang-like; a pair of symphysial canines on lower jaw; scales minute, typically smaller than eye diameter (except for those on posterior half of body) .......................... Odontamblyopus

4b. Head and body compressed, rather short, body depth 14.1-16.0 % of SL; teeth in outermost row of jaws close-set, flattened, not fang-like; no symphysial canine teeth on lower jaw; scales large, distinctly larger than eye diameter .............. Pseudotrypauchen