PIETSCH: OSTEOLOGY AND RELATIONSHIPS OF TETRABRACHWM 

 Supracleithrum 



Postcleifhrum 



Scapula 



Coracoid 



Cleithrum 



Radials 



Pelvic spine 



Pelvic bone 



Figure 14. — Medial view of right pectoral girdle, and pectoral 

 and pelvic fins of Tetrahrachnim ocellatum. AMS IB. 7178, 

 61 mm SL, Cartilaginous radials supporting pelvic fin rays and 

 cartilaginous distal radials supporting pectoral fin rays not 

 showTi; see text. 



an elongate, ventromedially directed extension 

 of the posttemporal. 



The supracleithrum, cleithrum, coracoid, and 

 scapula (Figure 14) are similar to those described 

 for other lophiiforms (Gregory 1933, fig. 265; 

 Pietsch 1972, 1974). A cleithral spine is absent. 

 There is a single rodlike postcleithrum. 



The pectoral fin is supported by three pectoral 

 radials (Figure 14). The two dorsalmost radials are 

 similar in size and shape. The third or ventralmost 

 radial is considerably larger; its expanded distal 

 portion bears the bases of nine unbranched, pec- 

 toral fin rays (each ray associated with a small, 

 cartilaginous distal radial; not shown in Figure 

 14). The pectoral fin itself is divided into two 

 portions: a dorsal portion consisting of four rays 

 that are interconnected by a membrane, and a 

 ventral portion consisting of five rays that are 

 similarly connected to each other, but also to the 

 lateral surface of the body. In a similar way, the 

 pectoral fin lobe is connected by a membrane to 

 the rays of the respective pelvic fin (Figure IB). 

 The pelvic bone, nearly as long as the ventralmost 

 pectoral radial, bears on its expanded distal end a 

 single spine and five unbranched pelvic fin rays 

 (each ray associated with a small, cartilaginous 

 radial; not shown in Figure 14). 



Skin spines. — Dermal spines are absent except 

 for the very rare occurrence of a tiny, crescent- 

 shaped spinule associated with an individual pore 



of the acoustico-lateralis system of the head and 



trunk. 



COMPARATIVE OSTEOLOGY OF 

 ANTENNARIOID FAMILIES 



The following discussion is based primarily on 

 an osteological comparison of a representative of 

 each of six major subgroups of the Antennarioidei 

 (here recognized as families; see Phylogenetic 

 Relationships and Appendix below): Antennarius 

 Daudin, thought to be the least derived genus 

 of the Antennariidae (see Phylogenetic Relation- 

 ships below); Tetrabrachium Giinther, the only 

 genus of the Tetrabrachiidae; Lophichthys Boese- 

 man, the only genus of the Lophichthyidae; 

 Brachionichthys Bleeker, the only extant genus of 

 the Brachionichthyidae (see p. 416); Chaunax 

 Lowe, the only genus of the Chaunacidae; and 

 Dibranchus Peters, an underived genus of the 

 Ogcocephalidae (see Bradbury 1967). Only those 

 comparative aspects that might have a bearing on 

 the phylogenetic interrelationships of these taxa 

 are discussed. 



Cranium (Figures 3-6, 15-19). — In Tetrabrachium 

 and Antennarius the ventral surface of the vomer 

 is strongly concave (as seen in anterior view. 

 Figure 6). A laterally compressed, keellike pos- 

 teromedial process emerges from the ventral sur- 

 face of this bone and fits within a deep groove 

 on the anteroventral surface of the parasphenoid; 

 the ventral margins of the posteromedial process 

 of the vomer and the anterior end of the para- 

 sphenoid are strongly convex (as seen in lateral 

 view. Figure 4). In all other antennarioids exam- 

 ined the posteromedial process of the vomer is 

 flush with the more or less flat ventral surface of 

 this bone; the ventral margins of the vomer and 

 anterior end of the parasphenoid (as seen in 

 lateral view) are straight to slightly concave. 



Other osteological variation in the crania of 

 antennarioids occurs primarily in the shape and 

 relative position of the frontal bones. In Anten- 

 narius, Lophichthys, Brachionichthys, and Di- 

 branchus (Figures 15-17, 19) the frontals are broad 

 and roughly triangular in shape, well separated 

 from each other anteriorly, but meeting on the 

 midline posteriorly. The narrow interorbital space 

 formed by these elements in Tetrabrachium is 

 absent (compare Figures 3 and 15). The anterior 

 ends of the frontals of Lophichthys are exception- 

 ally narrow, gradually tapering to a point (Figure 



397 



