260 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



MERLUCCIUS 



BRECMACEROS 



EUCLICHTHYS 



CADINAE (2) 

 LOTINAE (2) 

 EUCLICHTHYS ( u) 

 MURAENOLEPIS (2) 

 PHYCINAE 12) 

 MORIDAE («-5) 

 MELANONUS ( if- 5) 

 MERLUCCIUS (21 

 BRECMACEROS (2) 



MELANONUS 



HYPURAL RAYS 



Fig. 133. Numbers of hypural bones (in parentheses) and fin rays 

 supported by hypural bones in nine groups of gadiform fishes. Data 

 from Fahay and Markle (this volume) and original. 



TOTAL CAUDAL RAYS 



Fig. 132. Total caudal rays in eight groups of gadiform fishes. Data 

 from Fahay and Markle (this volume) and original. 



and including in addition to their gadiforms the polymixoids, 

 percopsiforms. batrachoids. iophiiforms, and gobiesocoids. 

 Gosline (1968) analyzed the characters used in defining the ex- 

 panded Gadiformes and concluded that ophidioids and zoar- 

 coids are perciform derivatives, while gadoids are widely sep- 

 arate and probably close to the percopsiforms (Gosline, 1963a). 

 Marshall and Cohen (1973), whom I follow for present purposes, 

 restricted the Gadiformes to the gadoids and macruroids but 

 did not consider the question of relationships. In the following 

 brief preliminary consideration of the order, I discuss several 

 characters, mention the groups that I think must be considered, 

 and outline some of my ideas about the course of evolution in 

 the gadiforms. 



Characters 



Several character complexes that require consideration are 

 discussed below. Others are noted later under groups in which 

 they occur. Additional relevant information is presented by Fa- 

 hay and Markle and Dunn and Matarese in subsequent sections 

 of this volume. 



Caudal fin.— Considering the fact that well over half the known 

 species of gadiform fishes lack the slightest vestige of a caudal 

 fin, it is a little astonishing how much importance has been 

 attached to the origin and homologies of the various skeletal 

 supports and of the fin rays themselves. There is no denying, 

 however, that when present the gadiform caudal complex is 

 unique in several respects. Most fish groups may be character- 

 ized by a set number of branched caudal rays. Furthermore, the 

 branched rays are generally supported by only hypurals. In gad- 

 iforms with tail fins, the number of branched caudal rays is 



highly variable, as is their skeletal support. Bregmaceros may 

 have as few as 1 2 branched caudal rays, most of which are 

 supported by hypurals, while at the upper end of the range, the 

 lotine Brosmc may have as many as 43 branched rays, which 

 are supported by hypurals. epurals, and haemal and neural spines. 

 This high degree of variation in an otherwise conservative an- 

 atomical complex lends credence to the idea of Boulenger(1902) 

 and Regan ( 1 903b) that the caudal fin of gadiforms is a structure 

 newly evolved from an essentially tailless condition such as that 

 of the macrourids or of some merlucciids. It was partly to test 

 Regan's hypothesis that Barrington (1937) compared the de- 

 velopment of the caudal fin of Gadus with that of Pleuwnectes 

 and concluded that, although the tail of Gadus was unique in 

 several respects, it could have been derived from an ordinary 

 homocercal tail that was less specialized than that of Pleuw- 

 nectes. I agree with Barrington. Barrington commented also on 

 the presence in gadids of a high number of procurrent caudal 

 rays, which he interpreted as being far posterior dorsal and anal 

 rays, so that the functional caudal of a cod is composed of 

 elements of three fins, dorsal, anal, and caudal proper. This 

 interpretation has been neither falsified nor verified by the study 

 of early life history stages. Barrington coined the term pseu- 

 docaudal for what he took to be this kind of fin. In his lectures 

 and during conversations with me. Ahlstrom disagreed with 

 Barrington's explanation and its acceptance by Marshall and 

 Cohen (1973) because procurrent rays lack pterygiophores. It is 

 instructive to note in this respect the caudal fin structure of 

 Muraenolepis (see Fig. 1 43 of Fahay and Markle in this volume), 

 which has confluent vertical fins and in which the distinctive, 

 elongate pterygiophores grade into hypurals. It is, in fact, im- 

 possible to distinguish between the last anal pterygiophore and 

 the first hypural or parhypural. But see Fahay and Markle later 

 in this volume. 



A variety of controversial interpretations (Gosline, 1963a; 

 Monod, 1968; Rosen and Patterson, 1969) have been advanced 

 concerning supposed sequences effusions and deletions of bony 

 elements in gadiform tails. This particular use of caudal fin 

 structure in phylogeny has yet to be proven, as few hypotheses 

 have been verified or falsified. 



For purposes of classification within the order, at least four 



