no. 3647 PERCIFORM FISHES — GOSLINE 31 



visionally in the Xiphioidei. What appear to me to be the more 

 important unifying elements of the Xiphioidei, as understood herein, 

 are the following: 



Vertebrae 23-26. Pelvic fins, if present, with not more than 

 three rays. Pectorals inserted low on sides. Dorsal and anal fin rays 

 at least somewhat more numerous than the vertebrae. Anterior 

 interneurals interdigitating between the skull and the vertebral 

 column. Frontal bones without a median crest (though the supra- 

 occipital extends forward over the frontals in Luvarus). Nasal bones 

 forming a rigid portion of the head skeleton (or possibly absent in 

 Luvarus: see Gregory and Conrad, 1943, p. 254). 



The Xiphioidei seem to have originated among the basal percoid 

 stock, though no modern percoid group suggests any obvious rela- 

 tionship with the xiphioids. That the group is an old one, extending 

 back at least to the Eocene, is well attested to by fossil evidence 

 (though the usual attribution of the Palaeorhynchidae, with 50-60 

 vertebrae, to the xiphioids seems dubious). 



Suborder Scombroidei 



The fishes herein included in the suborder Scombroidei are the 

 Scombridae as defined by Kegan (1909a), Fraser-Brunner (1950), 

 Collette and Gibbs (1963) and the trichiuroid fishes, i.e., the families 

 Gempylidae (cf. Matsubara and Iwai, 1958), the Trichiuridae (cf. 

 Tucker, 1956), and the Scombrolabracidae (Roule, 1922). The Istio- 

 phoridae, Xiphiidae, and Luvaridae, usually included in the Scombro- 

 idei (e.g., Regan, 1909a; Gregory and Conrad, 1937, 1943), herein 

 have been removed to a separate suborder, Xiphioidei, for reasons 

 given in the previous section. 



Among the trichiuroid families, the relationship between the Gem- 

 pylidae and the Trichiuridae has never, to my knowledge, been ques- 

 tioned. Scombrolabrax, discussed below, has been placed near the 

 Gempylidae since its discovery in 1922. 



Again, a postulate of relationship between the Scombridae and the 

 trichiuroid families, particularly the Gempylidae, generally has been 

 accepted. The only question has been whether or not the two groups 

 should be placed together in a single suborder (e.g., Regan, 1909a) 

 or allocated to separate suborders (e.g., Regan, 1929). It is true that 

 the principal evolutionary trends in the two groups have been very 

 different. That of the trichiuroids has been toward large-fanged, 

 ribbon-shaped forms, whereas the scombrids have developed into the 

 bulky, powerfully swimming tunas. Nevertheless, in many of what 

 would appear to be basic structures, the trichiuroids and scombrids 

 overlap. Indeed, the presumed gempylid Lepidocybiwm shows so many 



