A New Genus and Species of the Shallow-Water Anglerfish Family Tetrabrachiidae (Teleostei: Lophiiformes: Antennarioidei) from Australia and Indonesia

A new genus and species of anglerfish, Dibrachichthys melanurus, of the antennarioid family Tetrabrachiidae, is described on the basis of 42 specimens collected in near-shore coastal waters of Queensland, Northern Territory, Western Australia, and the Aru Islands, southeastern Indonesia. It differs most strikingly from its sister species, Tetrabrachium ocellatum, the only previously described tetrabrachiid, in having the pectoral fin entire, rather than having the rays divided into two distinct sections, a feature that was heretofore diagnostic for the family. The new taxon is diagnosed, described, and compared osteologically with its sister taxon using high-resolution, X-ray computed tomography.

Fig. 1

Dibrachichthys melanurus, new genus and species, holotype, QM I.37271, female, 48 mm SL, (A) dorsal, (B) lateral, and (C) ventral views.

Fig. 2

X-ray CT scans of the anterior skeleton of tetrabrachiids, left lateral views: (A) Dibrachichthys melanurus, new genus and species, paratype, QM I.36578, male, 34 mm SL; (B) Tetrabrachium ocellatum, QM I.30596, male, 43 mm SL. Note especially differences in the shape of the frontals and parietals (highly elevated in D. melanurus, forming a deep cranial depression), and in the size of the third (ventralmost) pectoral-fin radial and pelvic bone and fin. C 20, 21 = 20^th and 21^st pre-ural centra; F = frontal; P = parietal; PB = pelvic bone; PR 3 = third pectoral-fin radial; Pt = pterotic; Ptt = posttemporal; S = sphenotic; Sp 2 = second dorsal-fin spine; Sp 3 = third dorsal-fin spine.

Fig. 3

X-ray CT scans of the head skeleton of tetrabrachiids, dorsal views: (A) Dibrachichthys melanurus, new genus and species, paratype, QM I.36578, male, 34 mm SL; (B) Tetrabrachium ocellatum, QM I.30596, male, 43 mm SL. Note especially the differences in the shape of the frontal bones, each with a median flange approaching its counterpart on the midline in D. melanurus; rounded and diverging from the midline in T. ocellatum. LE = lateral ethmoid; remaining abbreviations as given in Figure 2.

Fig. 4

X-ray CT scans of the head skeleton of tetrabrachiids, anterior views: (A) Dibrachichthys melanurus, new genus and species, paratype, QM I.36578, male, 34 mm SL; (B) Tetrabrachium ocellatum, QM I.30596, male, 43 mm SL. Note especially the differences in the shape of the frontal bones: strongly elevated, each with a median flange approaching its counterpart on the midline, and a large anterolateral surface, forming (together with the respective sphenotic and lateral ethmoid) a deep, semi-circular, protective cavity for the eye in D. melanurus; but low and rounded, diverging on the midline, forming a relatively shallow, oval, orbital cavity in T. ocellatum. Abbreviations as given in Figures 2, 3.

Fig. 5

X-ray CT scans of the axial skeleton of tetrabrachiids, left lateral views: (A) Dibrachichthys melanurus, new genus and species, paratype, QM I.8500, female, 46 mm SL, showing anteriorly directed dorsal-fin rays that serve to carry egg clusters (see Fig. 2), a kind of egg-brooding apparently unique to tetrabrachiids; (B) Tetrabrachium ocellatum, QM I.30596, male, 43 mm SL. Note especially differences in the length of the pectoral-fin rays: reaching far beyond the origin of the unpaired fins in D. melanurus, but extending back only slightly past the origin of the anal fin in T. ocellatum; and placement of the posteriormost pterygiophores of the dorsal and anal fins: lying between the neural and haemal spines of the fifth and sixth vertebral centra in D. melanurus, between the neural and haemal spines of the fourth and fifth vertebral centra in T. ocellatum. C 4, 5 = 4^th and 5^th pre-ural centra.

Fig. 6

An egg cluster attached to the anteriormost dorsal-fin rays of Tetrabrachium ocellatum, NTM S.10081-004, female, 50 mm SL. Photo courtesy of Helen K. Larson and the Museum and Art Gallery of the Northern Territory, Northern Territory, Australia.

Fig. 7

Known geographic distribution of Dibrachichthys melanurus. A single symbol may indicate more than one capture.

Contributor Notes

Associate Editor: C. J. Ferraris.

¹ School of Aquatic and Fishery Sciences, and Burke Museum of Natural History and Culture, University of Washington, Campus Box 355020, Seattle, Washington 98195-5020; E-mail: (TWP) twp@u.washington.edu; and (RJA) schoenrj@u.washington.edu. Send reprint requests to TWP.

² Queensland Museum, P.O. Box 3300, South Brisbane, Queensland 4101, Australia; E-mail: (JWJ) Jeff.Johnson@qm.qld.gov.au.

Received: 14 Oct 2008

Accepted: 12 Feb 2009