PIETSCH: OSTEOLOGY AND RELATIONSHIPS OF TETRABRACHWM 



Figure 20. — Premaxillae, left lateral views: A. Antennarius 

 sanguineus, LACM 8125, 76 mm SL; B. Lophichthys boschmai, 

 UW 20773, 47 mm SL: C. Brachionichthys hirsutus, AMS 

 IA.6064, 69 mm SL; D. Chaunax pictus. UW 20770, 90 mm SL; 

 E. Dibranchus atlanticus, MCZ 51257, 105 mm SL. 



Opercular apparatus (Figures 9, 21-25). — The 

 opercle and subopercle of Antennarius , Tetra- 

 brachium, and Brachionichthys are similar except 

 in the following details: both elements are con- 

 siderably reduced in size in Tetrabrachium and 

 Antennarius (Figures 9, 21); in contrast to the 

 smooth, slightly concave (sometimes deeply in- 

 cised), posterior margin of the opercle of Anten- 

 narius, Tetrabrachium, and Lophichthys, the 

 posterior margin of this bone in Brachionichthys 

 is broken into numerous, weakly ossified, bony 

 filaments (Figure 23A); in contrast to the rela- 

 tively broad, spined subopercle of Antennarius 

 and Lophichthys, the subopercle of Tetrabrach- 

 ium and Brachionichthys (Figures 9, 23A) is a 

 narrow, crescent-shaped element lacking a sub- 

 opercular spine. 



In contrast to the small opercle and subopercle 

 of Antennarius, Tetrabrachium, Lophichthys, 

 and Brachionichthys, those of Chaunax and Di- 

 branchus (Figures 24, 25) are greatly enlarged 

 and expanded posteriorly. A we 11 -developed sub- 

 orpercular spine is present in Chaunax, but ab- 

 sent in Dibranchus. 



The interopercle of Antennarius, Lophichthys, 

 and Brachionichthys (Figures 21-23) is similar 

 to that of Tetrabrachium; the interopercle of 

 Chaunax and Dibranchus (Figures 24, 25) is 

 much more slender an*., elongate. 



Branchial arches (Figures 11, 28-32). — Pharyngo- 

 branchial I is represented by a simple, rod-shaped 

 element in Tetrabrachium, Antennarius, and 

 Lophichthys (Figures 11, 28, 29). In the single 

 specimen of Chaunax examined pharyngobran- 

 chial I is Y-shaped (Figure 31). This element is 

 toothless in Antennarius, Tetrabrachium, and 

 Chaunax, but bears a series of approximately 

 eight small teeth in Lophichthys (Figure 29). 

 Pharyngobranchial I is absent in Brachionichthys 

 and Dibranchus. Pharyngobranchial IV is absent 

 in all antennarioids. 



In Tetrabrachium , Antennarius, and Lophich- 

 thys (Figures 11, 28, 29), epibranchial I is tri- 

 radiate in shape, toothless in Antennarius and 

 Tetrabrachium, but bearing a single row of about 

 13 srpall teeth in Lophichthys (Figure 29). A 

 similarly shaped epibranchial I, associated with 

 three and two tooth plates is present in Chaunax 

 and Dibranchus, respectively (Figures 31, 32). An 

 L-shaped epibranchial I, associated with a single 

 tooth plate, is present in Brachionichthys (Figure 



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