'-.■ \ 



174 



■ . ■.: i ■' ' . "■ 'f r> fc .■■ ■^\::,^' 



evolved independently iny4. atronasus andy4. brevis on one hand, and all of the 

 species in the clade above node E. The second possibility is that paired caecae was 

 the ancestral condition of all species of Ageneiosus, and that a secondary reversal 

 occurred separately iaA.piperatus and A. pardalis. Both possibilities are equally 

 Kkely, but there are no corroborative data to support either one. Interpretation of 

 the evolution of swimbladder caecae is further compHcated by the condition in 

 Tetranematichthys, in which there is a single, extremely large posterior caecum. 

 Species in the outgroups examined lack any caecae, so the absence of any is 

 considered to be the plesiomorphic state for all ageneiosids. Thus, the phylogenetic 

 reconstruction provided by an analysis of other characters is uninformative to an 

 understanding of the evolution of swimbladder caecae. This situation can only be 

 redressed by examination of additional characters, including a broader comparison 

 with auchenipterid genera, to determine if convergence has occurred in 

 swimbladder structure. Moreover, homoplasy of meristic characters requires that 

 future studies include more in-depth analysis of additional characters, structural or 

 otherwise, to test the hypothesized phylogenetic reconstruction presented here. 



i V 



