The proximal elements supporting the teleost dorsal fin have been variously 

 termed radials and/or pterygiophores. Primitively in teleosts, there are three 

 elements supporting each ray of the median fins: a relatively long, tapered internal 

 element, usually interdigitating with neural spines of the vertebrae (and, thus, 

 sometimes called the intemeural); a short, medial element; and a small, often 

 cartilaginous, distal element, that articulates directly with the lepidotrichium. The 

 positional description of these elements is what is important, whether they are 

 called radials or pterygiophores. > , ».- ^.^ , . ' 



Among spiny-rayed fishes, in general, the middle element is often fused to 

 the proximal bone. In catfishes, the middle elements of both the dorsal and anal-fin 

 rays are absent as separate ossifications (Fink and Fink 1981), but they typically 

 remain evident as cartilaginous blocks. Furthermore, the distal elements are usually 

 reduced to round cartilaginous nodules located between the bases of the soft fin 

 rays. Weitzman (1962) made the distinction that a pterygiophore is composed of 

 radials, which may or may not become fused. Sometimes, when the proximal and 

 medial elements are fused, they are collectively called a basal. In spite of the 

 distinction between pterygiophores and radials that is occasionally made, some 

 authors have used the terms interchangeably. I follow Lundberg (1982) and 

 Schaeffer (1987) in loosely applying the term "pterygiophore" to the combined 

 proximal and medial elements, and the term "radial" or "distal radial" when referring 

 to the distal cartilaginous element. ' '' ' 



In most catfishes, the pterygiophores associated with the first two fin-ray 

 elements are exceptionally modified to form part of the spine-locking mechanism, as 

 described in detail by Alexander (1965) and Royero (1987). In many catfishes, the 

 expanded anterior pterygiophores, and sometimes more posterior ones, loosely 

 contact or even suture with the neural spines of the vertebral column. In 

 ageneiosids, both the first and second pterygiophores are expanded as laminar 





