ways toothless; pharyngobranchials consisting either of a 

 toothless suspensory element followed by three elements 

 bearing small but protruding or minute nonprotruding 

 teeth, or a toothless suspensory element (absent in some 

 Acanthostraclon) followed by two elements, one or both 

 of which bear minute nonprotruding teeth; epi- 

 branchials always four; gill rakers always present along 

 anterior edge of fifth ceratobranchial (posterior edge of 

 last gill slit); caudal fin supporting structures extremely 

 consolidated, the epural, hypural, parhypural, and cen- 

 trum elements fully fused into a single plate; haemal 

 spine of penultimate vertebra either autogenous or fused 

 to its centrum; neural arch of the last vertebra com- 

 plete, the canal accommodated in a tube through the 

 plate exiting on the posterior half of the dorsal edge, 

 while the haemal arch is either complete and the canal 

 accommodated in a tube through the plate or the arch is 

 essentially absent, the haemal region of the plate solid 

 and not pierced by the canal; uroneurals never present; 

 vertebrae normally 9 -I- 9 = 18 or 10 -I- 8 = 18, but 9 -I- 10 

 = 19 in one species, and always 9 or 10 abdominal verte- 

 brae; the first 2 to 5 vertebrae reduced in size at least 

 anteroposteriorly and at least partially fused to the rear 

 of the skull; 7, more rarely 8, abdominal vertebrae with 

 neural spines anterior to the first basal pterygiophore of 

 the soft dorsal fin; 3 to 5 caudal vertebrae posterior to the 

 last basal pterygiophores of both the soft dorsal and anal 

 fins; usually no more than 2, rarely 3, soft dorsal fin basal 

 pterygiophores placed between successive neural spines; 

 most neural spines positioned strongly obliquely in rela- 

 tion to the axis of the vertebral column; haemal spines 

 above the anal fin basal pterygiophores relatively 

 shorter, either rudimentary or well developed as antero- 

 posteriorly expanded plates but never long and shaftlike 

 and not penetrating into the proximal region of the series 

 of anal fin basal pterygiophores, and at least some of 

 these haemal spines markedly different in shape and size 

 from the neural spines above them; soft dorsal fin basal 

 pterygiophores 8 to 10; anal fin basal pterygiophores 8 to 

 10; prominent thin lateral flanges not present on the soft 

 dorsal and anal fin basal pterygiophores; distal pteryg- 

 iophores either absent or unossified in both the soft dor- 

 sal and anal fins; 4 to 6, or about half, of the anal fin 

 basal pterygiophores with only their distal ends placed in 

 the midline of the body, their proximal regions in- 

 creasingly divergent variously to the left and right of the 

 midline in the musculature bordering the rear of the ab- 

 dominal cavity; no spiny dorsal fin and hence no spiny 

 dorsal fin basal pterygiophores, but a supraneural ele- 

 ment present anteriorly from the dorsal end of the first 

 basal pterygiophore of the soft dorsal fin, this supraneural 

 element representing a modified basal pterygiophore, per- 

 haps the supraneural strut of balistids; epipleurals and 

 ribs never present; uppermost pectoral fin ray either of 

 two relatively well-developed halves of about equal length 

 (aracanids) or of a single piece bearing a foramen basally 

 (ostraciids); actinosts inflexible and articulated by 

 suturing to one another and to the scapula and coracoid; 

 coracoid and cleithrum enlarged; coracoid expanded 

 ventrally, as wide as or wider there than dorsally, with 



prominent broad flanges; coracoid with or without a pos- 

 terior prong along its posterodorsal edge, the prong when 

 present not so well -developed or closely associated with 

 the lowermost actinost; scapular foramen always com- 

 plete; cleithrum with an anterior flange from its lower 

 anteromedial edge; postcleithrum usually with two dis- 

 tinct halves, rarely as a single piece, the bone directed 

 posteriorly or only slightly obliquely downward and 

 variously slightly to enormously expanded posteriorly 

 and ventrally into a flat relatively thin plate, but never 

 as a long sturdy rod; nearly the entire length of the supra- 

 cleithrum overlying the cleithrum, or cleithrum and 

 postcleithrum, and the supracleithrum very firmly held 

 to them and the posttemporal; Baudelot's ligament os- 

 sified as a stout heavy rod between the posterior region of 

 the parasphenoid and the region of articulation of the 

 supracleithrum, cleithrum, and posttemporal; posttem- 

 poral usually relatively large; palatine an elongate block 

 of bone representing an enlarged foot of the T-shaped 

 balistid palatine and firmly sutured along all but the dis- 

 tal end of its medial surface to the ectopterygoid and 

 mesopterygoid while its distal end is held by ligament 

 primarily to the vomer; vomer much enlarged, having 

 either a strongly laterally expanded anterior end and a 

 relatively short posterior tapering shaft fitting into a 

 shallow concavity in the parasphenoid (aracanids) or a 

 strongly expanded lateral surface throughout its length, 

 so that the bone is more or less square and has a flat- 

 tened posterior surface that sutures to the similarly flat- 

 tened anterior end of the parasphenoid (ostraciids); ven- 

 tral edge of the ventral flange of the parasphenoid 

 laterally expanded slightly to moderately and only par- 

 tially along its length (aracanids) or well expanded along 

 all of its length anterior to the level of about the pre- 

 frontal (ostraciids); ventral flange of the parasphenoid 

 without a deep indentation at about the level of the pre- 

 frontal; parasphenoid with a high dorsal flange in the 

 medial septum of the orbit which sutures broadly or only 

 slightly with long anteroventral extensions of the ptero- 

 sphenoids into the medial septum; the medial edges of 

 the pterosphenoids not in contact in the posterior wall of 

 the orbit, well separated there; myodome small or ab- 

 sent; apposed surfaces of the parasphenoid and basioc- 

 cipital not excavated and no canal between them leading 

 anteriorly into the myodome cavity; epiotics not in con- 

 tact medially on the posterior surface of the skull, widely 

 separated there by the more posteriorly placed supraoc- 

 cipital; supraoccipital either with or without a posterior 

 crest, but never with an anterior crest on the surface of 

 the main body of the bone; prootic shelf usually relative- 

 ly larger, always with a prominent ventral or ventro- 

 lateral flange from its lateral edge; the major foramen in 

 the prootic shelf relatively large and elongate, and not 

 completely enclosed by the prootic, being bounded 

 laterally by the prootic and medially by the para- 

 sphenoid; anterior edge of the upper part of the preoper- 

 culum articulated below along the rear edge of the 

 hyomandibular but above to a groove on the lateral sur- 

 face of the hyomandibular; hyomandibular a greatly ex- 

 panded plate, without much of a shaftlike portion. 



