Revision of the Genus Chiasmodon (Acanthomorpha: Chiasmodontidae), with the Description of Two New Species

Marcelo R. S. Melo

doi:10.1643/CI-08-048

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Article Contents

Abstract
MATERIALS AND METHODS
DISCUSSION
MATERIAL EXAMINED
Acknowledgments
LITERATURE CITED

Editorial Type:

Article Category: Research Article

Online Publication Date: 03 Sept 2009

Revision of the Genus Chiasmodon (Acanthomorpha: Chiasmodontidae), with the Description of Two New Species

Page Range: 583 – 608

DOI: 10.1643/CI-08-048

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Abstract

Chiasmodon is a genus of meso- and bathypelagic fishes, commonly known as swallowers. The genus has a wide distribution in the Atlantic, Pacific, Indian, and Southern Oceans. Five species previously described are considered valid and two are described as new: C. niger, from tropical North Atlantic, including the Gulf of Mexico and Caribbean; C. subniger from the eastern Pacific; C. braueri from the Indian, western and Central Pacific, and western South Atlantic; C. microcephalus, from southern parts of the Atlantic, Indian, and Pacific, and the Southern Ocean; C. pluriradiatus from tropical Atlantic, Indian, and Pacific; C. asper n. sp., from the temperate North Pacific; and C. harteli n. sp., from the temperate North Atlantic. Chiasmodon bolangeri is considered a junior synonym of C. niger, and C. lavenbergi a junior synonym of C. pluriradiatus. Taxonomic keys to the family Chiasmodontidae and to the species of Chiasmodon, as well as updated maps of distribution are provided.

Fig. 1

Schematic of a hypothetical Chiasmodon: in (A) sensory system of head; (B) ventral elements of gill arch in dorsal view; (C) right premaxilla; and (D) right dentary. Abbreviations are as follows: (A) ESC, epiphyseal branch of supraorbital sensory canal; IO, infraorbital canal; MD, mandibular canal; OT, otic canal; PrO, preopercular canal; SO, supraorbital canal; ST, supratemporal canal; T, temporal canal; TR, trunk canal; ang, angular; den, dentary; dst, dermosphenotic; ext, extrascapular; fr, frontal; io 1–6, infraorbitals 1–6; mx, maxilla; mst, mesethmoid; lls, lateral-line scale; na, nasal; pa, parietal; pmx, premaxilla; pop, preopercle; pto, pterotic; ptt, posttemporal; so, supraoccipital; (B) bh, basihyal; bb, basibranchial; cb, ceratobranchial, ch, ceratohyal; eh, epihyal; hh, hypohyal. Some of the conditions presented may not be present at the same time in an individual specimen (for specific variation, see Figures 4, 5, and 6).

Fig. 2

Distribution of Chiasmodon: in (A) C. niger (circle), C. braueri (asterisk), and the type locality of C. bolangeri (X; species valid as C. niger, see text); in (B) C. pluriradiatus (cross), and C. subniger (diamond); and in (C) C. asper (star), C. harteli (square), and C. microcephalus (triangle). Solid symbols stand for type localities, open symbols for specimens examined in this work; each symbol may represent more than one sampling locality or lot of specimens.

Fig. 3

Chiasmodon niger in lateral view: (A) BMNH 1863.12.12.4, holotype, 76.9 mm; (B) ISH 9171, 117.3 mm.

Fig. 4

Schematic of the most common configurations of sensory pores in head of Chiasmodon (see text for details and variation): (A) C. niger and C. microcephalus; (B) C. subniger; (C) C. asper; (D) C. pluriradiatus and C. braueri; and (E) C. harteli.

Fig. 5

Schematic of dentition in premaxilla of Chiasmodon (see text for details): (A) C. braueri, C. harteli, C. niger, C. microcephalus, and C. subniger; (B) C. pluriradiatus, C. asper.

Fig. 6

Schematic of teeth on ventral elements of gill arch (see text for details): (A) C. braueri; (B) C. harteli and C. niger; (C) C. pluriradiatus and C. asper; and (D) C. subniger and C. microcephalus.