Figure 264.— Dorsal 



views of skulls of: 



left, Lagocephalu» apadiceus, 



98.2 mm SL, Mozambique; 



right, L. lagocephalus, 



214 mm SL, Malpelo Islands. 



the frontal in pachygaster or any of the other species of 



Sphoeroides with a moderately wide, evenly tapered 

 frontal would lead to exactly the condition of the frontal 

 found in L. scleratus. 



These species of Sphoeroides also share with L. 

 scleratus the generalized features of the absence of a dor- 

 sal flange of the parasphenoid in the orbit, while most of 

 them have numerous small to minute teeth on the first 

 pharyngobranchial, except for S. pachygaster in which it 

 is a toothless plate similar to that of most Lagocephalus. 

 Most of these species of Sphoeroides have several small 

 rounded trituration teeth in a single row to either side of 

 the midline and none in the lower jaw, just as in Lago- 

 cephalus, and most also have both a dorsal and ventral 

 hypohyal, a probable condition of the ancestral stock of 

 Lagocephalus since L. laevigatus retains two hypohyals. 

 A few of these species of Sphoeroides have moderately to 

 well -developed prootic prongs in the rear of the orbit 

 representing the remains of the dorsal roof of the 

 myodome, and a few have interhyals, all conditions to be 

 expected in the ancestral stock of Lagocephalus. 



In short, Lagocephalus seems relatively clearly to have 

 been derived from a Sp/ioeroides-like ancestral group, 

 the connection between the two being most clearly seen 

 in L. scleratus and in any number of relatively gener- 

 alized species of Sphoeroides, as well as particularly in S. 

 pachygaster. I would suspect that it was the same line of 



Sphoeroides radiation leading to the deepwater pachy- 

 gaster that gave rise to Lagocephalus, at a time before 

 the few specializations of pachygaster (loss of teeth on 

 first pharyngobranchial, loss of spines, complete loss of 

 remnants of the dorsal roof of the myodome) had become 

 established, this line leading to a form with two lateral 

 lines, moderately folded olfactory epithelium, and the 

 skeletal structure of scleratus and external character- 

 istics ofinermis (except with spines on the belly and dor- 

 sum), with the scleratus -like line diverging in external 

 and a few internal features associated with its more rapid 

 swimming and the inermis-like line developing a more 

 specialized skull structure, this latter line being 

 ancestral to most of the other species of Lagocephalus. 



Perhaps Sphoeroides was more widespread in the Indo- 

 Pacific than at present, and has subsequently become 

 confined to the Atlantic and eastern Pacific as it met 

 superior competition in shallow Indo-Pacific waters from 

 the plethora of genera of tetraodontids evolving there, 

 and was able to remain in the Indo-Pacific only in the 

 form of a single deepwater species. 



Fraser-Brunner (1943) associated Amblyrhynchotes 

 and Torquigener (including Fugu) with Sphoeroides (as 

 the Sphoeroidinae) and Lagocephalus (the Lago- 

 cephalinae, together with the Sphoeroidinae comprising 

 the Lagocephalidae), on the basis of their having the 

 sphenotics small and separated from the prefrontals by 



327 



