NOTE Mollet et al Re identification of a lamnid shark embryo 



871 



eral compression of its snout. This presumably was a result 

 of being fixed and presetted in a nairow jar, and the weight 

 of the massive yolk stomach providing sufficient force to 

 compress the snout. The cranium had an extremely short 

 ethmoid region compared with that of postnatal lamnids, 

 which was exaggerated by snout foreshoilening. The ros- 

 tral cartilages were only basally developed and partially 

 crushed and had no well-developed rostral node. The pro- 

 truding orbits were large but short and the otic capsules 

 were more elongated than in postnatal lamnids. 



In other features, the cranium agreed with that of the 

 Uchida embryo and postnatal shortfin makos (Table 3). 

 The bases of the lateral rostral cartilages were positioned 

 on the nasal capsules, as in white and mako sharks, rather 

 than on the preorbital processes as in Lamna (Compagno, 

 1990). The ethmoid region across the nasal capsules was 

 relatively narrow, as in shortfin makos and porbeagles; 

 white sharks, in contrast, have notably broad nasal cap- 

 sules (Haswell, 1885; Parker, 1887; Compagno, 1990). The 

 cranial roof of white sharks has an epiphysial bar and 

 epiphysial fenestrum just behind the anterior fontanelle, 

 but this is absent in postnatal crania of shortfin makos, 

 porbeagles, and Sanzo's embryo (Compagno, 1990). 



The upper jaw and the pectoral girdle of the Sanzo 

 embryo agreed with those of the Uchida embryo and 

 postnatal makos (Table 3). The palatine processes of the 



palatoquadrate were low, elongated, and ventrally bent or 

 twisted as in shortfin makos. White sharks have higher, 

 straight, and thicker palatine processes (Compagno, 1990). 

 Porbeagles, postnatal shortfin makos, and Sanzo's embryo 

 all have an unsegmented metapterygium in their pectoral 

 fin skeletons, whereas white sharks have a transversely 

 segmented basal metapterygium (Compagno and Gott- 

 fried, unpubl. data). 



The precaudal vertebral count of Sanzo's embryo (110 

 centra in total, including 73 monospondylous and 37 dip- 

 lospondylous centra) fell close to the average for shortfin 

 makos, whereas white sharks and porbeagles have fewer 

 precaudal vertebrae (Table 3). The caudal vertebrae count 

 of Sanzo's embryo (77) falls in the range of both white 

 sharks and shortfin makos and is shghtly greater than 

 caudal counts for porbeagles. Caudal vertebral counts from 

 radiographs are often unreliable in newborn and late fetal 

 sharks because of poor calcification of the posterior end of 

 the vertebral column. The caudal vertebrae of the Sanzo 

 embryo were difficult to count without dissection because 

 they were small and are not expected to be fully formed 

 until late in embryonic life (Springer and Garrick, 1964). 

 The Uchida embryo is of similar length but is considerably 

 heavier compared to the Sanzo embryo, but its vertebral 

 column was insufficiently calcified and we were unable to 

 obtain a precaudal vertebral count from the x-rays taken. 



