REVIEW OF THE PARROTFISHES 7 



The anatomical characters considered most important to the 

 phylogeny of the Scaridae are (1) number of rows of pharyngeal teeth 

 on each upper pharyngeal bone, (2) presence or absence and nature of 

 incisorlike external teeth on dental plates, (3) overlapping of jaws at 

 tips, (4) number of median predorsal scales, (5) number of rows of 

 scales on cheek, (6) number of branched pectoral fin rays. In con- 

 sidering the evolutionary history of the genera of scarid fishes, one 

 must decide what is the most primitive nature of each of these 

 characters. 



The upper pharjmgeal bones are paired, each having three rows of 

 teeth, or a reduced number of rows (see pis. 1-5). In every species 

 examined the reduction occurs on the outside row, this outer row 

 being rudimentary. It is concluded, therefore, that three fvilly 

 developed row^s of teeth on each bone represents the most primitive 

 condition, whereas the most speciaHzed condition occurs when only 

 one row is present, as in Scarops. 



2. The presence of incisorlike teeth, slanting forward at the front 

 of the jaws in Cryptotomus much like those of labrid fishes, indicates a 

 relationship with the family Labridae. The reductioa of these incisor- 

 like teeth to an imbricate pattern externally on the dental plate in 

 Calotomus, and their complete absence on such genera as Scarus and 

 Sparisoma, indicates the most primitive condition as occurring in 

 CryptotomiLS. 



3. In labrid fishes generally, the enlarged incisorlike teeth at the 

 front of the jaws slant forward, a condition much like that observed 

 in Cryptotomus. In Nicholsina the lower teeth curve more abruptly 

 toward the upper teeth than the upper curve toward the lower teeth. 

 Usually a dental plate occurs inside these external teeth. Apparently 

 very early in the phylogeny of scarid fishes two very major divisions 

 arose, in one of which, the Sparisomatinae, the dental plate of the 

 lower jaw closes over the edge of the dental plate of upper jaw. In the 

 other phyletic line Scarinae, the dental plate of the upper jaw closes 

 over the edge of the dental plate of the lower jaw. Thus it appears 

 that the primitive condition obtains when the dental plates and teeth 

 directly oppose each other or slant far forward. 



4. The conclusions reached with regard to the fu'st three characters 

 indicate that with specialization the number of rows of teeth are 

 reduced on the pharyngeals, the incisorlike teeth are lost, and a fused 

 dental plate becomes the functional biting mechanism. It is assumed 

 that the function of feeding is of greater importance to parrotfishes 

 than such characters as number of scales on the head or number of 

 pectoral rays. This leads to the conclusion that the number of median 

 predorsal scales could vary widely among species of parrotfishes 

 without greatly affecting the survival of the various species. It was 



