DUNN: DEVELOPMENT AND DISTRIBUTION OF LEUROGLOSSUS SCHMIDTI 





D 0) 



P3 P] 



m in 





co to 



J* p. (V. fv. c*. ^. p. (* 



O 01 



m n 



o 0) 



o o 



CO CO 



O 03 



O O 



! 2 m 2 



_ TD "O "D ^ o 



; a. 5 o. 5a (i iiji 



long (Table 4). However, most of these bones are 

 not consistently ossified until the specimens 

 reach transformation. 



In larvae 26-31 mm long, most cranial struc- 

 tures begin to ossify, although a number of bones 

 are not consistently ossified until the larvae 

 transform (Table 4). Most structures in the oro- 

 mandibular region and opercle series are con- 

 sistently ossified in 30 mm larvae. Conversely, 

 most elements of the olfactory, orbital, and otic 

 regions as well as most bones of the neurocrani- 

 um and hyoid arch are not consistently ossified 

 until the larvae transform. Some bones (nasal, 

 antorbital, prefrontal, epiotic, extrascapular, 

 supraoccipital, and ectopterygoid) become con- 

 sistently ossified after transformation; others 

 (interhyal and all of the branchial arches), how- 

 ever, are not consistently ossified even in the lar- 

 gest transformed juveniles examined (51.6 mm). 



Axial Skeleton 



The haemal spine on preural centrum 1 (PUi) 

 commences ossification in some larvae 23-24 mm 

 long [I follow Ahlstrom and Moser (1976) in con- 

 sidering the centrum adjacent to the anterior 

 ural centrum as preural centrum 1; this would be 

 PU 2 of Monod ( 1968)]. The neural spine on PUi is 

 partially ossified in some larvae 29-30 mm long. 

 Neural and haemal spines apparently ossify rap- 

 idly during transformation; all are fully ossified 

 in transformed juveniles. The sequence in which 

 neural and haemal spines ossify could not be de- 

 termined. 



The first vertebra to ossify is the first ural cen- 

 trum (Ui), which is ossified in some larvae 29-30 

 mm long. Centra, like neural and haemal spines, 

 ossify rapidly as the larvae transform. Generally, 

 either only the first ural centrum accepts aliza- 

 rin stain or all the vertebrae are ossified. In one 

 specimen 30.6 mm long, however, 50 centra are 

 partially ossified. In this specimen, centra 6-41 

 are completely encircled with red, whereas cen- 

 tra 1-5 and 42-50 are ossified only at the ventral 

 surface. This pattern of ossification suggests that 

 the preural centra initially ossify near the center 

 of the vertebral column and ossification proceeds 

 both anteriorly and posteriorly. 



Other structures of the axial skeleton ossify 

 during or after transformation (Table 4). Proxi- 

 mal radials of the dorsal and anal fins begin 

 ossifying after transformation; medial and distal 

 radials are not ossified in any samples examined. 

 Ribs, on centra 2 to 27-28, are ossified on all trans- 



33 



