In order to understand the developmental relationship between the cycloid scale and ctenoid scale in teleosts, the distribution of the two types of scales in Flounder (Paralichthys olivaceus), Large Yellow Croaker (Larimichthys crocea) and Small Yellow Croaker (Pseudosciaena polyactis) were investigated (Fig. 1). By comparing with the different morphological structures in different scales stained with alizarin red, we found not only cycloid scale and ctenoid scale with typical structures, but also scales with transitional morphological features between typical cycloid scale and ctenoid scale in one fish body of flounder, large yellow croaker and small yellow croaker, that indicated the typical ctenoid scale might be developed from the cycloid scale (Fig. 2). The different types of scales in the same body section were found in the flounder at 100 days after hatching and adults, which provided the further indication for the developmental relationship between the cycloid scale and ctenoid scale (Fig. 2). We further investigated the numbers of cycloid scales and ctenoid scales in different body parts in both L. crocea and P. polyactis, and found out no significant difference of the numbers of cycloid scales or ctenoid scales between left and right body sides (Table 1, 2). We also did not found any difference between the scale number in dorsal area, lateral line area and abdomen area. However, the significant difference in number was found in the different body areas along anterior to posterior axis in both L. crocea and P. polyactis (Table 1, 2). The number of cycloid scales decreased gradually from the head to tail, on the contrary, the number of ctenoid scales increased gradually from anterior to posterior (Fig. 3, 4). More ctenoid scales distributed in the body rear in the two species of croakers, indicating the croaker might use ctenoid scales as generator vortex to improve swimming efficiency.