870 



Fishery Bulletin 100(4) 



because of wrinkling of the skin (Francis, personal 

 observ.) Lohberger (1910) did not observe a sec- 

 ondary keel in preserved salmon shark (Lamna 

 ditropis ) embryos, although this keel is present in 

 postnatal specimens (Compagno, 1984). 



Dentition 



The first observations by naked eye and magnify- 

 ing lens suggested a tooth formula of 8-0-7 for the 

 upper jaw. However, the functional tooth row (i.e. 

 the outermost row containing erect, functional 

 teeth) of the upper right jaw was not completely 

 filled by teeth; it comprised eight visible teeth (in 

 file positions 2-6 and 8-10) and six gaps (in file 

 positions 1, 7 and 11-14 (Table 2). The gaps in the 

 functional row were indicated by the presence of 

 teeth in the replacement rows. The gap in file 1, 

 the broken tooth in file 2 (the 2nd tooth on the left 

 was not erect), and the teeth in files 3-6 (labeled) 

 are in focus in Fig. IC. The largest functional 

 tooth in file 6 had an enameloid height of 2.4 mm. 

 The tooth formula for Sanzo's embryo indicated 

 that an embryo of this size and developmental 

 stage has the full adult complement of replace- 

 ment tooth files in the upper jaw; two anteriors, 

 one intermediate, eight laterals, and three poste- 

 riors (Table 2). The first and second replacement 

 rows contained teeth in all file positions, indicat- 

 ing an eventual tooth formula of 14-0-14. 



The functional tooth extracted from the 5th file 

 in the left upper jaw (E2 -2 mm) was fanglike 

 and was without any lateral flattening and we 

 considered it to be an embryonic tooth (Fig. ID I. 

 The replacement tooth behind it was slightly 

 cui-ved, had little lateral flattening, and a thin 

 layer of tissue still covered the apex (E2 -2. .3 mm 

 and H -2.9 mm) (Fig. IE). We suggest that this 

 tooth is also an embryonic tooth. The relative po- 

 sition of these two teeth is as shown in Figs. ID 

 andE. 



The relative heights of the embryonic teeth in 

 the upper jaw differed considerably from those of 

 postnatal shortfin makos (Table 2). The first two 

 teeth in the Sanzo embryo were much smaller 

 than the teeth in files 3-8; the largest tooth was 

 in file 6. In postnatal shortfin makos, the first two 

 teeth are the largest, followed by a much smaller 

 third tooth and smaller ones in files 4—13 (Table 2). 



The tooth formula for the lower jaw was less certain. 

 Our initial obsei-vation with magnifying lens indicated 4- 

 0-7. Sanzo ( 1912) reported 4-0-4 and we agree with Sanzo 

 that the third lower tooth was the most prominent. 



Mucous denticles 



Mucous denticles covered the palate and the tongue. Micro- 

 scopic investigation revealed that the wartlike struc- 

 tures were round and had a circular, flat base and a 

 small upward-pointing center cusp. No ridges were noted 



^°o 



oo 



• o oo<* 



o 



,°(p 



Total length (m) 



Figure 2 



Relationships between selected morphometries and total length of 

 Carcharodon carcbarias lopen circle) and hums oxynnchus (filled 

 square). Sanzo embryo data (Sanzo, 1912 and our study) are mdi- 

 cated by dual symbols. (A) Ratio of mouth width to mouth length 

 (MOW/MOD. (B) Ratio of eye length to eye height (EYL/EYH). (C) 

 Relative position of the origins of anal and second dorsal fins (PAL- 

 PD2). (D) Relative position of first dorsal fin origin and pectoral fin 

 free rear tip (PDl-PRT). (E) Eye length (EYL as 9, TLl. 



between the cusp and the base. The mucous denticles were 

 small and far apart on the tongue, slightly larger and closer 

 together on the palate, and largest ( -0.4 mm diameter) and 

 packed together in the region close to the cartilage of the 

 upper jaw. There were few in the region close to the lower 

 jaw and on the terminal part of the tongue. 



Skeletal anatomy 



The cranmm of the Sanzo embryo differed notably from 

 that of postnatal lamnids. The chondrocranium of the em- 

 bryo was evidently damaged and foreshortened by the gen- 



