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V 



Weberian A pparatus and Axial Skeleton 





% The ageneiosid Weberian apparatus involves the six anteriormost vertebrae, 

 the rear of the neurocranium, and the supporting elements of the rayed dorsal fin. 

 The most distinctive aspect of the complex is the presence of an elastic spring 

 mechanism, discussed below in greater detail. ;. ; \, ^ :„"\'^d^- 



The tripus of doradoids and some other catfishes (e.g., the Mochokidae) is 

 modified from the typical siluriform condition in having a recurved transformator 

 process that penetrates the peritoneal tunica of the swimbladder (Chardon 1968). 

 This is the condition in ageneiosids with large, free swimbladders, but in species 

 with encapsulated swimbladders (discussed below), the transformator process of the 

 tripus has an expanded, disc-like posterior lamina that contacts the swimbladder 

 anterodorsally (Fig. 8). The correlation between an enlarged transformator process 

 and an encapsulated swimbladder suggests that there has been some functional 

 compensation for auditory reception. The os suspensoria of ageneiosids are small, 

 ovoid elements attached ligamentously to the tripus and complex centrum (Fig. 7), 

 as in other doradoids (Chardon 1968, Ferraris 1988). I have not examined in detail 

 the structure and orientation of the remaining Weberian ossicles. 



Anteriorly the complex centrum is strongly sutured to the exoccipitals, which 

 is characteristic of all other doradoids (Royero 1987, Ferraris 1988). In addition, 

 the neural arches of the fifth and sixth vertebra are expanded into laminar 

 ossifications that suturally unite with the first and second dorsal-fin pterygiophores, 

 forming a rigid plate between the complex centrum and the dorsal fin (Figs. 17, 24). 

 Laterally, the parapophyses of the fifth and sixth vertebrae extend horizontally and 

 suture with each other and the posterior process of the epioccipital, forming a broad 

 laminar plate above the swimbladder (Figs. 3-6, 24). The extent of fiision of the 

 vertebral parapophyses with the epioccipital process is much more extensive than a 



