26 



G.J. HOWES 



P u2 puUul 



Fig. 15. Melanonus zugmayeri Caudal fin skeletons of A, 130mm SL and B, 100mm SL specimens. C, caudal fin musculature (although a 

 superficial layer of connective tissue and some muscle has been removed the vertebrae are exposed in situ as shown). 



nus (Macruronidae) as a composite unit incorporating an 

 accessory neural arch suggesting that the first centrum had 

 been incorporated in the 'basioccipital'. Since, however, 1) 

 ribs are always lacking from the first two vertebrae in 

 gadiforms, 2) Baudelot's ligament always occurs on the first 

 centrum and 3) an accessory neural arch does not occur above 

 aulopiforms, it seems untenable that incorporation has 

 occurred in macruronids. 



The caudal fin skeleton is lacking in the majority of 

 gadiform taxa but where it does occur its most significant 

 features are fusion of the upper hypurals and the presence of 

 X and Y bones (lost in some taxa, see above), both of which 

 contribute to the symmetry characteristic of 'supragadoids'. 

 The morid caudal fin skeleton is regarded as the plesiomor- 

 phic gadoid type since it approaches that of most other 

 teleosts in its asymmetry and in having distally separated 

 hypurals. In this latter respect, Melanonus demonstrates a 

 further derived condition in having the hypurals distally fused 

 (see further discussion on p. 30). 



Of particular note is the condition of the caudal fin 

 musculature (Fig. 15C) which differs from that described in 

 gadoids (Howes, 1991) where hypochordal longidorsales, 

 flexores dorsales and inferiores are absent, the interradiales 

 have a characteristic linkage pattern between the caudal fin 

 rays and are continuous with the dorsal and anal fin rays. 

 Howes (1991: 104) pointed out the absence of the latter in 

 Melanonidae, but overlooked the fact that the caudal fin 

 musculature more closely resembles that of other paracan- 

 thopterygians and acanthopterygians in having discrete dorsal 



and ventral flexores and an amalgamated segment of interra- 

 dialis musculature corresponding to the superficial interradia- 

 lis. 



Melanonus, Lyconus and Brosme are the only gadiform 

 taxa to possess a single dorsal fin, most have two and the 

 more derived Gadidae have three. Dorsal fin origin is usually 

 above the second and third neural spines, as in Melanonus, 

 but the origin of the second dorsal is variable, the radial 

 supporting the first ray of that fin being between the eight and 

 ninth, ninth and tenth or tenth and eleventh neural spines. 

 According to Inada (1989) the single dorsal fin of Lyconus 

 evolved from amalgamation of two separate fins. Inada's 

 evidence relies on a notch being present in the fin at a point 

 above the proximally curved thirteenth radial which lies 

 between the eighth and ninth neural spines which as just 

 noted is the region commonly associated with the origin of 

 the second dorsal fin. No similar 'evidence' occurs in Mel- 

 anonus. 



Among gadoids the first radial of the first dorsal fin usually 

 lies between the second and third neural spines, but this is 

 variable being between the first and second in gaidropsarids, 

 and in Bregmacerotidae the first radial has become directed 

 forward so that the first dorsal fin ray lies above the supraoc- 

 cipital. In macrouroids, the first supporting radial is also 

 usually between the second and third neural spines but 

 sometimes between the third and fourth. Percopsids, like 

 melanonids have the first radial between the third and fourth 

 neural spines. In ophidiiforms the position of the first radial is 

 variable and can lie between any of the neural spines from the 



