JOHNSON: PERCOIDEI 



479 



Table 120. Continued. Extended. 



pH-1-2; 3-4-UR 



5/3/2/2 



3/1/1/2 

 1-2; 3-4 



+ + 



Ct 



Cy 



Ct 



Cy 



( 1 972a) argued that the first three predorsal elements of percoids 

 may represent supraneurals. Ahlstrom et al. (1976) recognized 

 the importance and utility of considering patterns of predorsal 

 bones in early life history studies, and further developmental 

 studies could resolve the origin of these elements. 



The most common and presumably primitive number of pre- 

 dorsal bones in percoids is three; Table 120 shows that over 

 half of 91 percoid groups (families and incertae sedis genera) 

 have three predorsal bones exclusively, with three predorsals 

 occurring in at least some members of 66 groups. The first dorsal 

 pterygiophore inserts in the third intemeural space in at least 

 some members of 69 groups, bears two supernumerary spines 

 in some members of 69 groups and exhibits both conditions in 

 57 groups. Therefore, the most common and ostensibly prim- 

 itive predorsal formulae (using that defined by Ahlstrom et al., 

 1976) for the Percoidei are 0/0/0 + 2/ and 0/0 + 0/2/. The 0/0/1 

 pattern, considered by Smith and Bailey (1961) to be primitive 

 for percoids occurs in only six families, frequently in the more 

 derived members. Furthermore, Fraser (1972a) noted that der- 

 ivation of the 0/0/0 + 2/ or 0/0 + 0/2/ patterns from the 0/0/1 

 pattern by backward shift of the first dorsal spine, hypothesized 

 by Smith and Bailey (1961), is untenable and inconsistent with 

 pterygiophore interdigitation. On the other hand, the 0/0/0 + 2/ 

 pattern could be easily derived by a posterior shift of the first 

 dorsal spine in the 0/0/1 + 1/ pattern that characterizes many 

 beryciforms, including holocentrids and diretmids. This latter 

 pattern is found among percoids only in some ambassids. 



Departures from the primitive predorsal pattern have appar- 

 ently arisen independently in many families. In anterior shifts 

 of the dorsal fin origin a compound first pterygiophore with two 

 supernumerary spines is frequently retained, but it is invariably 

 absent in posterior shifts. A possible conclusion is that forward 

 shifts result from anterior displacement of the pterygiophores, 

 whereas posterior shifts result only from loss of spines. Reduc- 

 tions in numbers of predorsal bones to fewer than three are 

 almost certainly the result of simple losses as opposed to trans- 

 formations, even when these reductions are accompanied, as 

 they are occasionally (e.g., Chaetodontidae, Scatophagidae, Pen- 

 tacerotidae, Priacanthidae), by a forward shift of the dorsal fin 

 origin. Transformations of pre-existing predorsal bones to spi- 

 nous pterygiophores would require the unlikely addition of de 

 novo spines and distal radials, and modification of musculature. 

 More than three "predorsal bones" are found in at least some 

 members of 13 percoid groups, with a corresponding posterior 

 shift of the dorsal fin origin. The additional elements are usually 

 distinguishable from the anterior three ("true") predorsals. In 

 Bathyclupea, Braminae, some carangids, Congrogadidae, Mene, 

 Neoscorpis. Platax. some pempheridids and Toxotidae, these 

 additional spineless elements (designated P in Table 120) re- 

 semble pterygiophores, may have separate distal elements, and 

 often articulate with succeeding similar elements or with the 

 anterior-most spine-bearing pterygiophore. In Bathyclupea and 

 Toxotidae. they are also separated from the true predorsals by 

 one intemeural space. In the remaining groups with more than 

 three "predorsals" (some percichthyids and centrarchids, Brink- 

 manella and Leptohrama). the additional elements are not mor- 

 phologically distinguishable from the anterior three, but, as in 

 the other groups, the dorsal fin originates posterior to the third 

 intemeural space (except in Brinkinanella), and it seems likely 

 that these elements were also derived from pre-existing pteryg- 

 iophores. Studies of the sequence of development of predorsal 



