Watson: Early life history stages of Cheilopogon xenopterus 



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of each haemapophysis. In 6.3-nim specimen last four 

 neural arches and spines broadening and by 8.2 mm 

 last six much broader than more anterior neural 

 arches and spines. These broad posterior neural 

 arches and spines provide the necessary attachment 

 surfaces for the large supracarinalis posterior, flexor 

 dorsalis, and flexor ventralis muscles (Winterbottom, 

 1974; Dasilao et al., 1996) which are involved in gener- 

 ating the strong caudal thrust required for gliding. 



Ossification of each vertebra begins ventrally. As 

 bone spreads dorsad from ventrum, ossifications also 

 form at bases of the two neurapophyses and spread 

 mesially and ventrad to complete centrum. Centra 

 apparently added from anterior to posterior, but uro- 

 style and penultimate centrum ossify before other 

 — caudal vertebrae. All vertebrae ossified by 5.2 mm 

 (Table 3). There are 42-44 vertebrae: 27-30 abdomi- 

 nal and 13-15 caudal (modally 29 -i- 14 = 43). 



Pleural ribs first visible in 6.3-mm specimen (Table 

 3 ). These ossify adjacent to parapophyses beginning 

 at third vertebra (at second vertebra on one side in 

 one specimen) and are added posteriorly. Epineural 

 intermuscular bones begin ossifying in myosepta 

 anteriorly, initially remote from vertebrae, by 8.2 mm 

 (Table 3), and pairs added posteriorly. Ossification 

 of each rib and epineural intermuscular bone is both 

 mesial toward adjacent parapophysis, and distal. Full 

 complements of both series not yet formed in largest 

 cleared and stained specimen. 



Caudal and pectoral are first fins to begin form- 

 ing. Hypural elements first visible in late stage-VIII 

 embryos, begin ossifying soon after hatching (by 

 2.9 mm). Retrorse basal spur forms on hypural 1 by 

 6.3 mm. Uroneural ossifying by 5.2 mm and epurals 

 1 and 2 by 6.3 mm. Epural 3 not clearly ossifying 

 until 8.2 mm. Principal caudal-fin rays begin to form 



