COMPAGNO and SPRINGER: NEW GEN'LS OF CARCHARHINID SHARKS 



er eyelid in adults, with nearly horizontal edge; 

 anterior nasal flap not greatly reduced; teeth 

 without postlateral cusplets; an interdorsal 

 ridge present; lateral trunk denticles much long- 

 er than wide in adults (about as long as wide 

 in Hypogaleus and Galeorhinus) ; and no ventral 

 lobe on caudals of adults. 



From the curious Le.pfocharias, logo differs 

 in having a transitional rather than internal 

 nictitating lower eyelid in adults; much larger 

 spiracles; no nasal barbel; very weak gynandric 

 heterodonty; teeth with primary cusps oblique, 

 not erect, and lacking cusplets; sharp-edged, 

 bladelike cutting teeth; fewer total vertebrae, 

 130 to 147 (198 to 214 in Leptocharias) ; spiral 

 intestinal valve with about 5 turns (14 to 16 in 

 Leptocharias) ; and an entire supraorbital crest 

 (reduced in Leptocharias to isolated preorbital 

 and postorbital processes) . 



lago can be distinguished from Hemitriakis, 

 Furgaleus, Scylliogalens, the Triakis-Miistelns 

 complex, Proscyllium, and Eridac^us by its more 

 lateral eyes, in dorsal view nearly touching head 

 rim, and its sharp-edged, monocuspidate teeth. 

 In addition, lago differs from He>nitriakis in 

 having a transitional rather than external nic- 

 titating lower eyelid, noncarinate posterior teeth, 

 more tooth rows (only 18 to 36/29 to 34 in 

 Hemitriakis) , weak transverse notches on teeth, 

 and no ventral caudal lobe. lago lacks the short, 

 thick, rounded snout, nasoral grooves, and molar- 

 iform teeth of Scylliogalens and also has fewer 

 tooth rows and series of teeth functional. Un- 

 like Furgaleus, lago lacks nasal barbels, erect 

 cusps on its lower anterolateral teeth, and a 

 ventral caudal lobe; also, lago (Figure 2) has 

 the nostrils definitely closer to the mouth than 

 the snout tip (about equidistant in Furgaleus) . 

 lago differs from most members of the Triakis- 

 Mustelus complex in having fewer tooth rows and 

 series of teeth functional; however, Triakis sem- 

 ifasciata rivals lago in these respects. lago does 

 not have a pavement of molariform teeth as in 

 Mustelus; also, its pelvic anterior margins are 

 less than half the length of pectoral anterior 

 margins (over half as long in Triakis-Mustelus) . 

 Finally lago contrasts with Proscyllium and 

 Eridacnis by its transitional, not rudimentary, 

 nictitating lower eyelid; monocuspidate poster- 



FiGURE 2, — lago omnnensis. A. Ventral side of head. 

 B. Dor.sal side of head. 



ior teeth (not comblike) ; dorsal fin base mid- 

 point closer to pectoral base termination than 

 pelvic origins (vice-versa in Proscyllium and 

 Eridacnis) ; second dorsal origin anterior (not 

 over or posterior) to anal fin origin; interme- 

 dialia of vertebral centra strong wedges (not 

 wedgelike in Proscyllium and Eridacnis) ; large 

 papillae absent from gill arches and buccal cavi- 

 ty; and nostrils farther apart. lago also lacks 

 the clasper hooks, scyliorhinoid color pattern, and 

 apparently the oviparous reproduction of Pros- 

 cyllium. 



GENERIC DESCRIPTION 



Head flattened, its length from snout tip to 

 fifth gill opening about i/i. total length. 



Eye openings dorso-lateral, not visible in 

 ventral view of head, openings elongate, about 

 twice as long as high, with a well-developed 

 posterior notch ; nictitating lower eyelid trans- 

 itional (Figure 3B), its edge nearly hoi'izontal; 

 secondary lower eyelid strongly differentiated, 

 its edge thin; subocular jjouch shallow, its lateral 

 surface bare of denticles. 



Slitlike spiracles, length about J'- eye length, 

 located about -- eye length behind and slightly 

 below posterior eye notch; external gill slits mod- 

 erately short, lengths in adults nearly equal, the 

 longest 1,4 to % eye length; nostrils located 

 about one-half as far from mouth as from snout 

 tip, well separated, without nasoral grooves, 

 widths about 1% to 2 times internarial dis- 

 tance, anterior nasal flap a short truncate lobe. 



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