Anatomical diversity.— The anatomical diversity of 

 this family has been treated in detail by Tyler (1968) and 

 the major features need be only briefly summarized here. 



The Recent species form a very slightly diversified 

 group of four rather finely split genera that in the near 

 past were all accommodated in one genus. The heavy in- 

 cisorlike teeth of Triacanthus, Pseudotriacanthus, and 

 Tripodichthys occur in an outer series of 10 in both jaws, 



the upper jaw with an inner series of four molariform 

 teeth and the lower jaw with two. In Trixiphichthys, 

 however, the teeth are smaller and the number of inner 

 series teeth in the upper jaw is reduced to two, while the 

 snout is longer and the mouth is narrower than in the 

 other three genera. A mesopterygoid is absent except in 

 Trixiphichthys, in which it is small. The caudal peduncle 

 is much shorter and the lateral line slightly less con- 



