Eoplectinae, that was ancestral to Triodon and the other 

 Tetraodontoidei. From the very fact of their close ances- 

 tor-derivative relationship, many of the characteristics of 

 the eoplectins and triodontids bridge what are otherwise 

 the morphological gaps between the known fossil and Re- 

 cent Balistoidei and Tetraodontoidei. 



SUBORDER BALISTOIDEI 

 (SCLERODERMI) 



Comparative diagnosis (contrast with that of the 

 Tetraodontoidei). — Teeth relatively large (small in one 

 highly specialized genus of triacanthodids) and discrete 

 separate units protruding out from sockets in the jaws, 

 except in the Eocene eoplectin triacanthodids in which 

 the teeth are small, nonprotruding, and fully incor- 

 porated into the matrix of the jaw bones just as in many 

 of the Tetraodontoidei, to which they are ancestral; den- 

 taries and premaxillaries never fused to their opposite 

 members, except in at least some eoplectins; the medial 

 articulation of the premaxillaries to one another not 

 strengthened by alternating emarginations and inden- 

 tations; posttemporal present, except in one highly 

 specialized species of monacanthid; urohyal present; pel- 

 vis present, except in the ostracioids, the most specializ- 

 ed superfamily; pelvic fin present, at least as a rudiment 

 at the posterior end of the pelvis, except completely ab- 

 sent in many of the more specialized monacanthids and 

 in all ostracioids; palatine relatively small and not firmly 

 sutured to both the ethmoid-vomerine region and the 

 pterygoid arch, except probably so sutured in the eoplec- 

 tins; myodome with a complete dorsal roof present, ex- 

 cept small to absent in ostracioids; prootic shelf under 

 the orbit present, except in triacanthoids, the most 

 generalized superfamily, and in several highly specializ- 

 ed monacanthids; supracleithrum placed vertically or 

 only slightly obliquely to the axis of the skull; scapular 

 foramen complete, except in two highly specialized 

 species of monacanthids; scapula with a knob or crest for 

 articulation with the uppermost pectoral fin ray; at least 

 some of the distal pterygiophores of the soft dorsal and 

 anal fins ossified, except in ostracioids; spiny dorsal fin 

 varying from six well -developed spines to a single slen- 

 der spine, or, in ostracioids, absent altogether, but when 

 present having its origin above or close behind the skull; 

 first branchiostegal ray relatively unmodified, without 

 an inturned dorsomedial edge. 



Infraorder Triacanthoideo 



Comparative diagnosis (contrast with that of the 

 Balistoideo), which is also that of its only contained 

 Superfamily, the Triacanthoidea.— Premaxillary with 

 a well-developed pedicel or ascending process, the 

 pedicel usually a sturdy rodlike shaft (but variously 



modified in the two long-snouted genera of triacantho- 

 dids) sliding along the dorsal surface of the ethmoid 

 and, sometimes, vomer as well; premaxillary movably 

 articulated with the maxillary, allowing for a slight 

 protraction of the upper jaw; maxillary deeply indented 

 dorsally for articulation with the anterior end of the 

 palatine, except in the long-snouted triacanthodids; 

 palatine usually with a squarish or oblong major portion 

 (as seen laterally) from which arises an anterior prong for 

 articulation with the maxillary, although much modified 

 in the long-snouted triacanthodids, but never as a T- 

 shaped bone or a simple rod, or as a bony column sutured 

 to the palato-pterygoid arch; ethmoid with a more or less 

 evenly convex upper surface, without a laterally ex- 

 panded dorsal or dorsolateral region and always nar- 

 rower dorsally than ventrally; no prootic shelf developed 

 under the orbit in front of and above the major articula- 

 tion of the posterior region of the parasphenoid with the 

 prootics; dorsal end of the hyomandibular articulated 

 with the prootic, pterotic, and sphenotic; interoper- 

 culum long and, at least posteriorly, relatively deep and 

 flattened, never as a stout rod throughout its length, and 

 extending posteriorly well behind the level of the epihyal 

 and interhyal to approach closely and connect by a short 

 ligament to the anterior edge of the suboperculum; dor- 

 sal fin spines usually six, rarely only five, supported by 

 five or four, and rarely only three, basal pterygiophores; 

 the first dorsal spine not lockable in an erected position 

 through the agency of the second spine, but with an in- 

 dependent locking mechanism between the base of the 

 first spine and its basal pterygiophore; first basal pteryg- 

 iophore of spiny dorsal fin with a high dorsomedial 

 flange articulating through an anteroposterior canal in 

 the basal region of the first dorsal spine; pelvic fin con- 

 sisting of at least a large erectile and lockable spine, 

 sometimes followed by one to four rays of greatly varying 

 degrees of development, at about the middle of the 

 length of the pelvis, except in several Eocene 

 triacanthodids in which the spine may have been reduc- 

 ed in size and possibly absent; pelvis either shaftlike or 

 basinlike posterior to the pelvic spines and never with a 

 dorsal lobe posteriorly, but always with a laterally ex- 

 panded portion anterior to the spines; pelvis not par- 

 ticularly rotatable in life around its anterior articulation 

 with the cleithra and no expansible dewlap of skin pres- 

 ent between the posterior end of the pelvis and the anus; 

 one or two sets of uroneurals usually present; vertebrae 

 nearly always 8 -I- 12 = 20 (9 -(- 11 = 20 in one Eocene 

 species); three pharyngobranchials with prominent large 

 protruding teeth; posteromedial edges of epiotics slightly 

 to decidedly inturned to form, in association with the 

 exoccipitals and neural spine of the first vertebra, a 

 pocket in which the shaftlike base of the first basal 

 pterygiophore of the spiny dorsal fin is held, with the 

 probable exception of the Oligocene triacanthid Crypto- 

 balistes: mesopterygoid in neither direct nor indirect 

 contact with the quadrate and ectopterygoid, except 

 sometimes very slightly so with the quadrate by the 

 agency of the symplectic making contact with both the 

 quadrate and mesopterygoid. 



