'-V-.' -kl 33 



Other authors (e.g., Chardon 1968, Roberts 1973) also remarked on the occurrence 

 of this state in various siluroids. ^^ 



The primitive condition of the swimbladder in siluroids is believed to be one 

 in which it consists of a large organ, free from the vertebral parapophyses, lacking 

 posterior chambers, and with the ductus pneumaticus emerging from the anterior 

 transverse chamber (Bridge and Haddon 1894; Alexander 1964; Howes 1983). 

 There is considerable variation involving the development of caecae and ossified 

 encapsulation of the siluriform swimbladder, and, in all probability, many of these 

 involve homoplasies (see morphological comparisons). Moreover, there are 

 incongruencies in swimbladder encapsulation involving taxa that also possess an 

 elastic spring apparatus, or ESA (Howes 1983). Based on features of the 

 swimbladder and Weberian apparatus, Howes (1983:fig. 22) placed ageneiosids 

 within a clade that included astroblepids and loricariids, despite his comments about 

 differences in the nature of encapsulation between ageneiosids and the latter two 

 taxa, and his suggestion that encapsulation has occurred independently in at least 

 two lineages. Apparently, Howes (1983) failed to observe the ESA in his 

 specimen(s) ofAgeneiosus, which led to his exclusion of the family from the clade 

 with other families having an ESA, which is where most authors have placed the 

 Ageneiosidae. . - 



In addition to the characteristics of the siluriform swimbladder as outlined 

 above, the genus Tympanopleura is paraphyletic, since other taxa with 

 unencapsulated swimbladders were described extragenerically (i.e., T. quadrifilis,A. 

 cUronasus,A. brevis,A. madeirensis). In a cladistic context, Tympanopleura was 

 diagnosed on the basis of a shared plesiomorphic character state, and, hence, does 

 not warrant generic status as a natural monophyletic group. Consequently, the three 

 species originally described in the genus Tympanopleura are herein allocated to the 

 gtnu^Ageneiosus (T.piperata [=A. piperatus], T. nigricollis [=A. atronasus], T. aha 

 [=A.brevis]). 



