HUBBS and WISNER REVISION OF THE SAURIES 



able fixed larva of Scomberesox ." Knowing C. 

 saira well as a moderately large and extremely 

 active surface fish leads us to emphatically disre- 

 gard its consideration as a larva. There is nothing 

 in the ontogeny of the four species of the family to 

 support the view that beaklessness arose from the 

 beaked condition. 



Thus, we arrive at the concept of a relatively 

 large and strong, beakless. surface-swimming fish 

 as the phyletically basic member of the Scombere- 

 socidae: Cololabis alone fits this concept. We 

 therefore assume that an immediate ancestor of C 

 saira gave rise to the other members of the family 

 and remains as a relic in the temperate waters 

 around the North Pacific, where it appears to re- 

 place Scumberesox completely. 



The Cololabis ancestor presumably gave rise to 

 Scomberesox through the development of a long 

 beak, by the loss of filaments on the egg, and 

 through a moderate increase in size and in aver- 

 age numberof gill rakers and vertebrae. Perhaps a 

 stock of the ancestor crossed equatorial waters in 

 some past cool period and became isolated when 

 the tropics again became warm; differentiation 

 may then have taken place. From cool South 

 Pacific waters the West Wind Drift may be as- 

 sumed to have transported the saury to the south- 

 ern parts of the Atlantic and Indian Oceans. From 

 the Cape region of Africa it could have been car- 

 ried far northward on the Benguela Current and 

 may somehow, at some time, possibly even in the 

 Pleistocene, have transgressed the tropics to gain 

 the favorable waters of the North Atlantic. Such 

 movements, however, are hypothetical. 



The origin of the dwarfs from a type or types 

 more like Cololabis and Scomberesox seems 

 hardly subject to doubt (as is indicated above). 

 While recognizing the many features, some deep- 

 seated and fundamental, wherein Elassichthys 

 and Nanichthys closely agree, and jointly contrast 

 with Cololabis and Scomberesox (Table 1), we 

 strongly favor, albeit somewhat intuitively, the 

 hypothesis that they are the products of conver- 

 gent evolution: that Elassichthys stemmed from 

 Cololabis (or an immediate ancestor of that 

 genus), and that (Nanichthys is an offshoot from 

 Scomberesox (or its immediate ancestor). 



Circumstances favoring the concept of a dual 

 origin of the two dwarf species follow. 



1) Characters held jointly by Elassichthys and 

 Nanichthys, in contrast with Cololabis and Scom- 

 beresox, are of the sort that might well be related 

 to dwarfing, and hence be susceptible to indepen- 



dent origin. The lack of the gas bladder seems 

 compensated for by the greatly reduced size of the 

 fish ( yielding relatively more surface and viscosity 

 per weight), and by the apparently weaker muscu- 

 lature. The single ovary may be related to the 

 minute size of the organ and the proportionately 

 immense size of the few ova containable at any one 

 time. The degeneration of the lateral line is a 

 common feature of dwarfed fishes. The great re- 

 duction in number of gill rakers would be ex- 

 pected, as the smaller number should give 

 adequate straining in a space so greatly reduced. 

 Reduced number of vertebrae and rays is a feature 

 of dwarfing, as Te Winkel (1935) showed in her 

 study of a neotenic goby, and as she and the senior 

 writer showed in an unpublished study of the ex- 

 cessively neotenic fish genus Schindleria (which 

 was originally misplaced in the Synentognathi, 

 though it is not so related — as Gosline ( 1959) has 

 shown). 



2) The agreement between Elassichthys and 

 Cololabis in the mere sharpening of the jaws (the 

 upper rounded in Elassichthys), without any real 

 beak development, is a compelling reason to re- 

 gard them as closely related. 



3) The circumstance that the gill rakers and 

 vertebrae are fewer in Cololabis than in Scom- 

 beresox. and about proportionately fewer in Elas- 

 sichthys than in Nanichthys is at least suggestive 

 evidence. 



4) The circumstance that Cololabis is some- 

 what smaller than Scomberesox , and that Elas- 

 sichthys is proportionately smaller than Nanich- 

 thys, seems to provide similar confirmatory 

 evidence. 



5) The mutual occurrence oi Elassichthys and 

 Cololabis in the Pacific Ocean, in part sympatri- 

 cally, and the mutual occurrence o^ Nanichthys 

 and Scomberesox in the Atlantic and Indian 

 Oceans, again in part sympatrically, provides 

 strong confirmatory evidence that Elassichthys is 

 the dwarf derivative of Cololabis and that Nanich- 

 thys stemmed similarly and independently from 

 Scomberesox. This hypothesis is diagrammed in 

 Figure 3A. On this concept, dwarfing and various 

 structural changes (diagrammed as "d g o"), in- 

 cluding the loss of the gas bladder and the change 

 to a single ovary, occurred twice, whereas the 

 evolution of a beak (marked as "b") occurred only 

 once. 



No such body of evidence seems advanceable for 

 the alternative hypothesis (Figure 3B) that 

 dwarfing and the ancillary changes occurred but 



525 



