PIETSCH: OSTEOLOGY AND RELATIONSHIPS OF TETRABRACHIUM 



Ceratohyal\ 



Dorsal 

 hypohyal 



Ventral 

 hypohyal 



Branchiostegal rays 



Figure lO. — Hyoid apparatus of Tetrabrachium ocellatum: 

 A. AMS IB.7178, 61 mm SL, left lateral view; B. Basihyal, 

 AMS IB. 7177, 56 mm SL, ventral view, anterior to the left. 



tached to each other and to the dorsal end of 

 epibranchials II through IV. Epibranchial I is 

 triradiate in shape, articulating with cerato- 

 branchial I proximally, bearing pharyngobranch- 

 ial I distally, and attached by a short ligament to 

 the proximal end of epibranchial II medially. 

 Ceratobranchials I through IV are toothless. The 

 expanded, proximal end of each ceratobranchial V 

 bears about 19 to 21 depressible teeth arranged in 

 two rows. Hypobranchial I is a simple, rod-shaped 



Hypobranchial II 



Hypobranchial I 



Ceratobranchial I 



Epibranchial I 



Pharyngobranchial 



Pharyngobranchial II 



Hypobranchial III 



'^ ^Ceratobranchial V 



Epibranchial IV 



Pharyngobranchial 



Figure ll. — Branchial arches of Tetrabrachium ocellatum, 

 AMS IB.7178, 61 mm SL. The ventral portion of the branchial 

 basket is shown in dorsal view, the dorsal portion (epibranchials 

 and pharyngobranchialsl is folded back and shown in ventral 

 view. 



element. Hypobranchials II and III are bifurcated 

 proximally. Ossified basibranchials are absent. 



14th pre-ura 

 centrum 



Figure 12. — Vertebrae, caudal skeleton, and median fins of Tetrabrachium ocellatum. AMS IB.7178, 61 mm SL. 



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