PIETSCH: OSTEOLOGY AND RELATIONSHIPS OF TETRABRACHIUM 



1903, 1912; Gregory 1933; Eaton et al. 1954; Monod 

 1960; Le Danois 1964, 1974, 1979; Field 1966; 

 Bradbury 1967; Rosen and Patterson 1969; and 

 additional references cited by Pietsch 1972, 1974, 

 1978, 1979), yet no published osteological informa- 

 tion on the genus Tetrabrachium is available. In 

 the following account only those comparative 

 aspects that differ from those previously described 

 in other anglerfishes are discussed. 



Cranium (Figures 3-6). — The ethmoid cartilage 

 of T. ocellatum broadly covers the posterior half of 

 the vomer meeting with the lateral ethmoids 

 laterally and the supraethmoid medially. The 

 supraethmoid forms a narrow, vertical inter- 

 orbital septum lying between, but well separated 

 from the orbital portions of the frontals. The 

 laterally compressed, ventral end of the supra- 

 ethmoid meets with the ethmoid cartilage ante- 

 riorly and lies within a groove on the dorsal 

 surface of the parasphenoid posteriorly. The dor- 



sal end of the supraethmoid is overlapped on each 

 side by central extensions of the frontals. Each 

 lateral ethmoid has a narrow, cylindrical poste- 

 rior portion that lies ventral to an anterior exten- 

 sion of the respective frontal, and a larger, ven- 

 trally directed, anterior portion that meets with 

 the ethmoid cartilage. 



The head of the vomer lies ventral to the 

 ethmoid cartilage. Its anterior margin is indented 

 medially. The ventral surface of the vomer is 

 strongly concave (as seen in anterior view, Figure 

 6). A laterally compressed, keellike posteromedial 

 process emerges from the ventral surface of this 

 bone and fits within a deep groove on the antero- 

 ventral surface of the parasphenoid; the ventral 

 margins of the posteromedial process of the vomer 

 and the anterior end of the parasphenoid are 

 strongly convex (as seen in lateral view. Figure 4). 

 Vomerine teeth are present in two lateral patches, 

 each patch containing approximately 25 teeth 

 arranged in perhaps three irregular rows. 



Parietal 



Sphenotic 



Posltemporal 



Supraethmoid 



Vomer 



Exoccipital 



— Neural spine of 22nd 

 pre-ural centrum 



Lateral ethmoid 



Epiotic 

 FIGURE 3. 



Frontal 



-Dorsal view of cranium of Tetrabrachium ocel- 

 latum, AMS IB.7178. 61 mm SL. 



Supraoccipital 



Pterotic 



Frontal 



.Sphenotic 



Parietal 



Posttemporal 



Exoccipital 



Lateral ethmoid 



Vomer 



Supraethmoid 



Parasphenoid 



Basioccipital 



Prootic 



Pterotic 



22nd pre-ural 

 centrum 



Figure 4. — Lateral view of cranium of Tetrabrach- 

 ium ocellatum, AMS IB.7178, 61 mm SL. 



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