THE OSTEOLOGY AND RELATIONSHIPS OF THE ANGLERFISH GENUS 

 TETRABRACHIUM WITH COMMENTS ON LOPHIIFORM CLASSIFICATION ' 



Theodore W. Pietsch^ 



ABSTRACT 



The shallow-water anglerfish, Tetrahrachium ocellatum, now represented by 36 specimens from 

 Australian. New Guinean. and Indonesian waters, is redescribed and compared osteologically with its 

 allies within the Antennarioidei. Phylogenetic analysis based on a search for shared, derived 

 characters shows that Tetrahrachium is most closely related to Antennarius, and is classified on this 

 basis as a sister-family of the Antennariidae. That the Tetrabrachiidae has entered a "new adaptive 

 zone" relative to the Antennariidae is evidenced moi-phologically by a number of unique derived 

 features. The most conspicuous of these include small, close-set eyes protruding from the dorsal surface 

 of the head, and a peculiar webbing between the pectoral fin and the body, and between the pectoral and 

 pelvic fins, characters that reflect a benthic existence in soft substrata (mud or fine sand). 



It is further shown that a group including the Antennariidae and Tetrabrachiidae forms the 

 primitive sister group of the Lophichthyidae and that these two groups together form the primitive 

 sister group of the Brachionichthyidae. Although evidence is provided to establish a sister-group 

 relationship between the Chaunacidae and Ogcocephalidae, no convincing synapomorphy is known at 

 the present time that will establish monophyly for a group containing all six families. An analytical 

 key to the major subgroups of the Antennarioidei is provided and a revised classification of the order 

 Lophiiformes is proposed. 



One of the more curious forms described by 

 Giinther (1880) in his report on the shore fishes 

 procured by the Challenger Expedition of 1873-76, 

 was a single specimen of an antennarioid angler- 

 fish from off the southern coast of New Guinea. In 

 reference to a peculiar, double pectoral fin and 

 numerous ocellilike markings on the dorsal half of 

 the body, the species was named Tetrahrachium 

 ocellatum. Since the original description perhaps 

 a dozen authors have cited Giinther (1880), but 

 none have been able to offer any new information 

 on this species other than a report of the discovery 

 of two additional specimens (Whitley 1935). For 

 the purposes of this study, 36 specimens of T. 

 ocellatum have been located, all collected from 

 Australian, New Guinean, and Indonesian waters 

 at depths of between approximately 5 and 55 m. 

 Although a close phylogenetic relationship with 

 the genus Antennarius has been implied (by 

 recognition of a subfamily Tetrabrachiinae of the 

 Antennariidae; Regan 1912, Berg 1940, Norman 



'Contribution No. 561, College of Fisheries, University of 

 Washington, Seattle, Wash. 



^College of Fisheries, University of Washington, Seattle, 

 WA 98195. 



Manuscript accepted February 1981, 

 FISHERY BULLETIN: VOL. '79, NO. 3, 1981. 



1966), no evidence for this alignment has been 

 provided. 



The objectives of this paper are to describe the 

 structure of T. ocellatum^ to compare it morpho- 

 logically with its nearest allies, and to specu- 

 late on the phylogenetic relationships of this and 

 other members of the suborder Antennarioidei. 

 Representatives of the six major antennarioid 

 subgroups (here recognized as families) are con- 

 sidered in detail. In addition to Tetrahrachium, 

 these are Antennarius Daudin, recognized here 

 as the least derived genus (see Phylogenetic 

 Relationships below) of some eight genera of 

 the Antennariidae (a modification of Schultz 

 1957; Pietsch in prep.); Lophichthys, a monotypic 

 genus recently described by Boeseman (1964) 

 and heretofore not adequately placed within any 

 higher taxonomic category (see Boeseman 1964 

 and Le Danois 1979); Brachionichthys Bleeker 

 (= Sympterichthys Gill), containing approxi- 

 mately four southern Australian species, and 

 recognized as constituting an antennarioid family 

 by nearly all authors since Regan ( 1912); Chaunax 

 Lowe, the only genus of the family Chaunacidae; 

 and Dibranchus Peters, an underived genus of 

 the Ogcocephalidae (see Bradbury 1967). 



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