COHEN: GADIFORMES 



261 



BREGMACEROTIDAE 



EUCLICHTHYS 



MERLUCCIUS 



10 20 30 40 50 



BRANCHED CAUDAL RAYS 



Fig. 134. Branched caudal rays in seven groups of gadiform fishes. Data from Fahay and Markle (this volume) and onginal. 



caudal fin characters require comment. They are: 1) presence 

 or absence of a caudal fin; 2) number of hypurals; 3) relationship 

 between branched caudal rays, hypurals, and procurrent caudal 

 rays; 4) presence or absence of X- Y bones. 



Although vestiges of a caudal fin are sometimes found in a 

 few macrourid species, it is essentially absent from all of them. 

 The same is true of the merlucciid genus Lyconus and also 

 Steindachneria. Loss of a caudal fin has certainly occurred two 

 times and perhaps more. 



The number of hypurals is a useful systematic character. There 

 are almost always 4 or 5 in morids and Melanonus, and almost 

 always 2 in gadids, Merliiccius. Bregmaceros, and Muraenolepis: 

 Euclichthys has 4, nearly fused to 2. 1 consider the lower number 

 to be an advanced character; the study of developmental series 

 has verified this interpretation for Raniceps at least (Dunn and 

 Matarese, this volume). Certainly the loss of hypurals, whether 

 through deletion or fusion has occurred several times in gadi- 

 forms. 



The evolutionary complexity of the caudal fin in gadiforms 

 is particularly apparent when considering the numbers of dif- 

 ferent kinds of caudal fin rays (Figs. 132-134 and Fahay and 

 Markle, this volume. Table 76). Morids in general have caudal 

 fins that are small and probably of reduced importance in pro- 

 pulsion, and which 1 interpret as a derived state; they also have 

 generally fewer total rays, which Fahay and Markle (this volume) 

 consider an ancestral state, and unbranched rays that tend to 

 be short and contribute little to overall caudal fin size; yet, 

 morids have 4-5 hypurals. Melanonus also has a weakly de- 

 veloped caudal fin but has 4-5 hypurals and many rays. Gadine 

 fishes on the other hand, have well-developed caudal fins with 

 many rays, both branched and unbranched, but have only 2 

 hypurals. Gadines are in general good swimmers, and one of 

 the most active of all, Pollachius vtrens, has the most total caudal 

 fin rays (70 in one specimen) of any gadiform fish. (Sluggish 

 fishes like the lotines, Brosme and Lota, also have numerous 

 caudal fin rays but have rounded caudal fins and must swim in 

 a very different way, probably using the caudal fin as an exten- 

 sion of the body rather than as an oar.) Although numbers of 

 different kinds of fin rays may prove useful in taxonomy, the 

 relationship of branched to unbranched or total caudal fin rays 

 is variable and has limited apparent value in the present context. 



Many gadiform fishes have in their caudal fin skeletons a pair 

 of bone splints resembling neural and haemal spines. These 

 structures have been mentioned in the literature as accessory 



bones or X and Y bones and have been interpreted as modified 

 relict pterygiophores or detached neural and haemal spines whose 

 centra have been lost (Rosen and Patterson, 1969). 1 agree with 

 Markle (1982) that the absence in any gadiform of X and Y 

 bones is a derived character. 



Dorsal and anal fins.— Gadiform fishes have 1, 2, or 3 external 

 dorsal fins and 1 or 2 external anal fins. The number, size, and 

 location of these fins have been used for hundreds of years to 

 characterize groups of species. Prior to the recognition of Mor- 

 idaeasa distinct family (Svetovidov, 1937), convergence in this 

 character was not recognized; most ichthyologists lumped 

 gadids and morids with similar fin patterns. 



Svetovidov ( 1948) assumed on functional grounds that a sin- 

 gle dorsal and single anal is the primitive condition and arranged 

 the gadid genera in a transition series based on increasing num- 

 ber of fins and the distance of their separation from each other. 

 His hypothesis is supported by the presence in all gadiforms of 

 a single, continuous, postanal series of pterygiophores, present 

 even over areas that lack fin rays. Complete or partial division 

 of the exterior fin has occurred several times, for example in 

 the gadines, Euclichthys. Merluccius. and in the morid genera 

 Mora, Halargyreus. Lepidion, Laemonema. and Tripterophycis. 



Although only a few gadiforms have a single dorsal fin, the 

 condition has a broad taxonomic distribution; examples are the 

 gadid Brosme. the merlucciid Lyconus. Melanonus, and the ma- 

 crouroidine rattails. Nearly all gadiforms have 2 or 3 dorsals, 

 but even in those with 3, there are only two series of pteryg- 

 iophores. From fewer to more dorsals would seem to be a rea- 

 sonable transition series. But it certainly has occurred more than 

 once, even within Gadidae, as Markle (1982) has demonstrated. 



Pectoral radials. — Mosx gadiforms have five pectoral radials. 

 Muraenolepis has more; Bregmaceros has fewer; both are in- 

 terpreted as derived conditions. 



First neural spine. — Many gadiforms have the first neural spine 

 closely adpressed to the occipital crest. I take this as a derived 

 character. Muraenolepis has a free spine, but it is modified by 

 the presence of a prominent wing-shaped enlargement extending 

 on either side of the occipital crest. 



Olfactory lobes. — In his classical monograph on the Gadidae, 

 Svetovidov (1948) discussed the position of the olfactory lobes 



