Family Balistidae 



Comparative diagnosis (contrast with that of the 

 Monacanthidae).— Teeth very sturdy, more or less in- 

 cisorlike, developed more for crushing than nibbling, four 

 outer and three inner on each premaxillary and four in a 

 single series on each dentary; pharyngobranchials con- 

 sisting of a toothless suspensory element and two uni- 

 serially toothed elements; fifth ceratobranchial toothed 

 but without gill rakers along its anterior edge (posterior 

 edge of last gill slit); three dorsal spines, the second more 

 than one-half the length of the first and ending ventrally 

 in large sturdy ventrally directed processes from either 

 side; dorsal fin spines supported by two basal pterygio- 

 phores and a supraneural strut; dorsal spines and their 

 basal pterygiophores placed behind the posterodorsal 

 apex of the skull, the anterior edge of the first basal 

 pterygiophore abutting against the rear of the postero- 

 dorsal surface of the skull; first basal pterygiophore with 

 a large lateral foramen to accommodate the ventral prong 

 of the second dorsal spine; supraoccipital large and stur- 

 dy, with a variously high (usually) to low (Rhinecanthus) 

 but sturdy vertical crest medially throughout its length, 

 the crest expanded laterally at its posterior end to help 

 support the anterior end of the first basal pterygiophore; 

 posterior region of the epiotic expanded dorsally, the 

 medial edges of the two epiotics well-separated dorsally, 

 bounding the posterolateral region of the deep foramen 

 in the skull between the epiotics and the supraoccipital 

 in which the short anteroventral shaft of the first basal 

 pterygiophore is held; palatine T-shaped, the long foot of 

 the T directed ventrally or posteroventrally to connect by 

 a short ligament with the anterior edge of the ec- 

 topterygoid; exoccipital meeting its opposite member in 

 the midline above the foramen magnum between the 

 medial edges of the bifid neural spine of the first 

 vertebra; prefrontal relatively large and heavy, firmly ar- 

 ticulated, often by interdigitation, with the frontal, 

 ethmoid, and parasphenoid; parasphenoid only slightly 

 expanded laterally just behind the orbit, the medial edge 

 of the pterotic on the ventral surface of the skull only 

 narrowly separated from its opposite member there by 

 the basioccipital and parasphenoid; parasphenoid much 

 expanded dorsally in front of the orbit, broadly overlying 

 the ethmoid and contacting the prefrontal; the laterally 

 expanded dorsal region of the ethmoid wide and thick. 



Figure 49.— Range of diversity in body 



form in the Recent Balistidae: Balistapus 



undulatus, left; Odonus niger, right. 



about as wide as or wider than the depth of the ventral 

 platelike portion; ventral platelike flange of the ethmoid 

 thick and sturdy, relatively shallow, not much if at all 

 deeper posteriorly than anteriorly, and broadly overlain 

 by the parasphenoid; posttemporal held in a deep groove 

 on the lateral surface of the pterotic; medial edge of den- 

 tary either denticulate or smooth; prootic shelf well 

 developed, extending forward at least to the level of the 

 middle of the orbit; posterior edge of supracleithrum 

 with a posteriorly directed process or hump; post- 

 cleithrum with a dorsal spur from its upper dorsal edge 

 supporting the ventral region of the tympanum 

 regardless of whether enlarged scales are present there or 

 not; postcleithrum either a single piece or divided into 

 dorsal and ventral segments; branchiostegal rays always 

 2-1-4; pelvis always with a dorsal lobe posteriorly on its 

 dorsal surface; encasing scales at the posterior end of the 

 pelvis in four segments, always flexible (least and only 

 slightly so in Canthidermis); a relatively well-developed 

 rudimentary pelvic fin element always present, running 

 the length of the last two segments and protruding to the 

 exterior through a foramen in the fourth segment (except 

 in Melichthys and Xanthichthys, in which the element is 

 reduced in size and does not protrude, and in Canthi- 

 dermis, in which the ray is an even smaller nubbin of 

 bone not protruding to the exterior); vertebrae 18 (7 + 

 11); vertebrae anterior to the first basal pterygiophore of 

 the soft dorsal fin always five, those posterior to the last 

 basal pterygiophores of both the soft dorsal and anal fins 

 always four; neural and haemal arches of the last cen- 

 trum relatively well developed although incomplete; the 

 last centrum with a vertical crest for muscle attach- 

 ment; uroneurals rarely present; an upper free hypural 

 always present; lateral flanges on the soft dorsal and anal 

 fin basal pterygiophores not ending distally in prominent 

 hooklike lateral expansions; the basal pterygiophores 

 extending proximally relatively closely to the neural and 

 haemal arches throughout the length of the series; the 

 great majority of the dorsal, anal, and pectoral fin rays 

 branched, only the first few rays, and sometimes the last, 

 being unbranched; scales large, with thick basal plates 

 and relative coarse spinulation, the basal plates broadly 

 overlapping (except in Canthidermis) and more or less 

 regularly arranged; scales above the pectoral fin base 

 usually enlarged and more or less separated, forming a 

 flexible covering to the tympanum (scales unmodified in 

 Canthidermis and only slightly modified but unenlarged 

 in Xanthichthys); species relatively large, adults usually 

 reaching well over 200 mm. 



