RAJU: THE GENUS MONOGNATHUS 



W U laningi, O M jisp»r$»ni, ^Ht bruuni. 



▲ iW 



ttaocsi , 



I H ohistromi, D M j§ss» 



FIGURE 3.— Distribution of the six 

 species of the genus Monognathus. 



One of the four specimens had been earlier 

 described by Roule (1934) as a semilarva of the 

 Lyomeri. According to Bertin the family Monog- 

 nathidae consists of a single genus, Monognathus , 

 with three species, none of which was designated 

 as the genotype. Myers (1940) recognized two 

 genera, Monognathus (genotype M. taningi 

 Bertin) and P has matostoma (new genus; genotype 

 M.jesperseni Bertin), on the basis of the number 

 of ethmoid teeth, position of the dorsal fin origin, 

 and nature of the vertebrae and caudal fin. 

 Bbhlke (1966) accepted Phasmatostoma as a 

 separate genus of the Monognathidae. As already 

 pointed out, M. isaacsi may well represent a third 

 genus of the family Monognathidae as the dif- 

 ferences between M. isaacsi and M. taningi are 

 even more pronounced than those between M. 

 taningi and M. jesperseni or M. bruuni, which 

 are separated as Phasmatostoma. M. ahlstromi 

 and M. jesse may also turn out to be new genera 

 as the caudal fin, which is a conservative struc- 

 ture in fishes, varies greatly in the two fishes. 

 However, I would restrain myself to introduce 

 new genera till a detailed study of many adult 

 and larval specimens is undertaken, as the stud- 

 ies on these fishes are based only on very few 

 specimens (1-2 in number), and even these are 

 only juvenile and metamorphic forms. 



Tchernavin (1947a) stated that there is no evi- 

 dence that the Monognathidae are related to the 

 Saccopharyngiformes. His arguments were based 



on some of the observations of Bertin such as the 

 absence of pectoral fin, presence of only one gill 

 arch, and other osteological characters. Green- 

 wood et al. (1966) and Bohlke (1966) considered 

 monognathids to be related to the Saccopharyngi- 

 formes. The general features of M. isaacsi — such 

 as the elongated suspensorium, presence of small 

 gill openings and four small gill arches, alter- 

 nating arrangement of gill filaments on the arch 

 as in Eurypharynx, voluminous stomach, oc- 

 currence of leptocephalus stage in the life his- 

 tory, the presence of the pectoral fin, and the 

 modified caudal fin — indicate that the Monogna- 

 thidae are related to the Saccopharyngiformes, 

 more closely to the Saccopharyngidae than to the 

 Eurypharyngidae. 



LEPTOCEPHALUS LATISSIMUS 

 SCHMIDT 1912 



Figure 4C 



Leptocephalus latus Schmidt 1909. SIO 66-353, 

 San Diego Trough, 32^40'N, 117=35'W, 480- 

 366 mwo, Tucker net, 1(30 mm), 23 Aug. 1950. 

 LACM, 6525-16, Santa Catalina Basin, 

 33n8'27"N-33"24'40"N, 118M4'00"W-118°51' 

 35"W, 0-213 mwo, IKMT, 1(39 mm), 22 Aug. 

 1963. LACM, 9830-10, No Name Basin, 32" 

 01'30"N-32"04'00"N, 117"59'00"W-117=56'00" 

 W, 600 mwo, IKMT, 1(40 mm), 28 July 1967. 



555 



