108 



plates, sutured together along their entire vertical lengths, and ventrally they are 

 sutured to laminar expansions of the neural spines of the fourth and fifth vertebrae 

 (Figs. 17, 24). Anterodorsally, the laminar plate suturally contacts the nuchal shield, 

 and posteriorly forms a medial plate for the dorsal-fin spine articulation. 



In doradoids and many other catfishes there are prominent dermal 

 components sutured posterodorsally to the rear of the skull, which are herein 

 coUectively termed the nuchal shield, or, individually, nuchal plates. In many 

 catfishes the supraoccipital has an expanded posterior process or spine, surrounded 

 partially by the nuchal plates. In doradoids a supraoccipital spine is absent, 

 however, but contact between the rear of the skull and the dorsal fin is made via a 

 broad, well developed nuchal shield. 



Currently there is no uniform agreement on the homology of the bones 

 forming the nuchal shield, and the problem is confounded by the terminology used 

 by differem authors. In his text, Ferraris (1988) equated the three elements typically 

 forming the doradoid nuchal shield with a dermal component of expanded basal 

 radials of the first three dorsal-fin rays, but, in his illustrations and list of 

 abbreviations, he called the elements of the nuchal shield pterygiophores (Ferraris 

 1988; cf. p. 44 and figs. 14-19). His description of these bones is problematic, 

 however, by his statement that "in the Ageneiosus group, the first pterygiophore is 

 either absent or lacks a dermal component, and, therefore, Ues entirely ventral to 

 the expanded second element" (Ferraris 1988:44). The anterolateral process of the 

 laminar plate described in the preceding paragraph was considered to be a first 

 proximal radial by Britski (1972) and a first basal radial by Royero (1987). I concur 

 with the last two authors regarding the identification of that bone, but I call it the 

 first pterygiophore, in order to be consistent with the terminology I have adopted 

 above. Both Britski (1972) and Royero (1987) referred to the three dorsal elements 

 forming the nuchal shield as nuchal plates (one through three by Britski; anterior, 

 medial, and posterior by Royero). 



