Development of the caudal skeleton of Leiognathus rivulatus was examined and described. Caudal skeletons of 3 genera of the family Leiognathidae, Leiognathus, SecrJtor, and Gazza are compared. The following features of caudal skeletons are found to be characteristic in the Leiognathidae.
1) Loss of the second uroneural.
2) Enlarged first epural.
3) Fusion between the first and second hypurals, and between the third and fourth hypurals.
4) Oar-like flange of heamal and neual spines on fourth preural centrum.
Leiognathus and Secutor have very similar structure in the caudal skeleton. The caudal skeleton of Gazza differs from those of other genera in following characters: 1) trace of fusion between PU1 and U1 is recognizable (not in other); 2) hypuropophysis is parallel with the body axis (slanted toward posterodorsal direction in others); 3) neural spine and hemal spines of PU5 are expanded (not in others).
