The sphenotics are relatively small, anvil-shaped bones forming the upper 

 posterolateral margin of the bony orbit. The infraorbital canal exits the sphenotic at 

 its anteriormost point and extends through an unossified portion for a short distance 

 before entering the last infraorbital. 



The dorsal profile of the neurocranium in all auchenipterids is considerably 

 different from that of ageneiosids, and varies widely among genera and species. In 

 auchenipterids, the sphenotics and frontals, and, to a lesser extent, the pterotics and 

 lateral ethmoids, are large elements forming a broad cranial vault. The sphenotics 

 are especially large and form a significant medial portion of the bony orbit. In some 

 groups (Auchenipterus and Epapterus) the sphenotics do not contact the 

 supraoccipital. A complete review of the auchenipterid neurocranium is beyond the 

 scope of this work, but it should be noted that there are a number of derived 

 features that serve to unite various auchenipterid genera (Britski 1972, Ferraris 

 1988). The general structure of the ageneiosid neurocranium is relatively primitive 

 in comparison to the skull morphology of both doradids and auchenipterids. 



Excluding the broadly flared ethmoid bones, the ageneiosid skull in ventral 

 profile is broadly rounded posteriorly and sharply tapered anteriorly (Fig. 7). The 

 parasphenoid is long and thin, contacting the vomer anteriorly and deeply suturing 

 with the basioccipital posteriorly. The vomer is broadly rounded anteriorly. 

 Ferraris (1988) felt that the nonangular shape of the vomer is a synapomorphy of 

 ageneiosids. Apparently this is a derived condition, inasmuch as the anterior end of 

 the vomer changes from a triangular shape to a more rounded shape during 

 ontogeny (personal observation of juvenile specimens). V 



The orbitosphenoid sutures anteriorly with the lateral ethmoid and extends 

 posteriorly for a short distance along the parasphenoid. The lateral ridge of the 

 orbitosphoid, which is moderately large in most other catfishes, is relatively small in 

 ageneiosids. 



