Family Tetraodontidae 



Comparative diagnosis (contrast with that of the 

 Diodontidae). — Teeth incorporated into the matrix of 

 the biting edge of the jaws as long slender rods; pre- 

 maxillaries and dentaries not fused to their opposite 

 members in the midline, the articulation strengthened 

 by interlocking emarginations; lateral surface of maxil- 

 lary neither deeply indented nor laterally flanged, the 

 surface relatively even; the jaws usually less massive; 

 small trituration teeth often present in the upper and, 

 less frequently, lower jaw as well, but seldom with a large 

 trituration plate in both jaws; first pharyngobranchial 

 with small or, usually, minute teeth, or sometimes tooth- 

 less, but second and third pharyngobranchials with small 

 teeth; dorsal hypohyal often absent; interhyal some- 

 times present; anterior edge of ectopterygoid distinctly 

 concave; ethmoid and vomer relatively well developed 

 and sturdy, although sometimes at least partially fused 

 together; palatine with a notched region posterodorsally 

 for firm articulation with a crested region of the vomer 

 and/or ethmoid, and never making contact with the fron- 

 tal; prefrontal usually well developed, absent only in two 

 closely related specialized genera, Xenopterus and 

 Chonerhinos; frontals less wide and massive, except in 

 Xenopterus; anterior end of parasphenoid less wide and 

 less deeply concave, the concavity filled by the posterior 

 articulating shaft of the vomer; rear margin of the orbit 

 formed by the frontal and sphenotic; sphenotic often 

 laterally expanded anteriorly, but never as a long, 

 slender lateral prong; frontal not in contact posteroven- 

 trally in the rear of the orbit with the prootic, separated 

 from it by the sphenotic and pterosphenoid; suboper- 

 culum without an anteriorly directed prong, and the in- 

 teroperculum articulated posteriorly by a short ligament 

 to the anterior edge of the operculum; supracleithrum 

 usually positioned at about a 45° angle to the axis of the 

 body, but with great variation between species on the 

 degree of obliqueness to the body; postcleithrum in two 

 pieces, and much longer than the distance along the 

 scapula to the lowest actinost; supraoccipital spine 

 laterally compressed and mainly in a vertical plane, al- 

 though its dorsal edge may be thicker than the ventral 

 plate; exoccipital condyles well developed; at least the 

 first two vertebrae anterior to the first basal pterygio- 

 phore of the dorsal fin without bifid neural spines, only 

 the first three to five abdominal vertebrae with bifid 

 divergent neural spines; none of the vertebrae with 

 prominent lateral flanges from the centra; neural spines 

 of the vertebrae supporting the basal pterygiophores of 

 the dorsal fin relatively normal long slender shafts pene- 

 trating relatively deeply the interspaces between the 



Figure 193.— Range of diversity in 



body form in the Recent Tetraodontidae: 



A. Lagocephalus spadiceus, 



B, Xenopterus naritua, 

 C, AmblyrhynchoteB pioaae, 

 D, Canthigaater rogtrata. 



pterygiophores; a supraneural element often present; at 

 least some of the basal pterygiophores of the dorsal and 

 anal fins usually, but not always, interdigitated with one 

 another; one or more of the more posterior abdominal 

 vertebrae usually, but not always, with a complete 

 haemal arch; none of the vertebrae posterior to the bases 

 of the last basal pterygiophores of the dorsal and anal 

 fins anteroposteriorly compressed, of about the same 

 centrum length as those more anteriorly; abdominal 

 vertebrae usually fewer in number than the caudal verte- 

 brae, sometimes of equal number but never of greater 

 number; dorsal and anal fins more anterior in position; 

 at least four vertebrae fully posterior to that whose hae- 

 mal spine is the last support of the last anal fin basal 

 pterygiophore; caudal fin supporting skeleton with a free 

 epural, one free uppermost hypural that in a few species 

 may be partially fused to the centrum, a free parhypural 

 and an autogenous haemal spine of the penultimate 

 vertebra; no prominent lateral flange present on the fus- 

 ed hypural-centrum plate; haemal canal penetrating the 

 last vertebral complex to exit between the parhypural 

 and fused hypural-centrum plate; caudal fin rays 11, the 

 two lowermost rays unbranched; scales always relatively 

 smaller, even when best developed, as in the moderate 

 quills of Torquigener piosae or the enlarged basal plates 

 of adult Ephippion guttifer. 



Comparative diagnoses of Subfamilies (Tetraodon- 



tinae and Canthigasterine). — Subfamily Tetraodonti- 

 nae: ethmoid varying from long to short, and of a vari- 

 ety of shapes, but never distinctly T-shaped in cross 

 section; supraoccipital with an only moderate to low 

 crest, usually arising from a flattened anterior region 

 of the bone from which it is prolonged posteriorly, the 

 posterior end of the crest not visible externally through 

 the skin; posterolateral region of frontal variously lateral- 

 ly expanded or not, but never as two flanges whose distal 

 ends closely approach or are in contact with one another 

 to form a bony well around the muscle mass leading to 

 the operculum; sphenotic a prominent component of the 

 dorsal surface of the skull, and usually extended antero- 

 dorsally at least a short distance forward of the rear edge 

 of the orbit; base of prefrontal always either in contact 

 with or in very close proximity to the vomer; trituration 

 teeth often present; one or two nostrils in a moderately 

 low to high sac or tube, or a single or bifid tentacle or 

 flap, but always conspicuous; lateral line conspicuous 

 (with the possible exception of the long-spined Tor- 

 quigener piosae); gill opening usually extending ven- 

 trally below the level of the middle of the pectoral fin 

 base; vertebrae modally 17 to 29; vertebral column 

 usually not highly arched anteriorly, the axis of the an- 

 terior portion of the column usually not especially ob- 

 lique to that of the skull; haemal arches and spines 

 usually not especially well developed on most of the ab- 

 dominal vertebrae. 



Subfamily Canthigasterinae: ethmoid long and T- 

 shaped in cross section, its upper surface a laterally ex- 



