122 



R.D. MOOI AND A.C. GILL 



METHODS AND MATERIALS 



Epaxial musculature/dorsal-fin pterygiophore associations 

 were studied in alcohol-stored specimens. An incision was 

 made through the skin along the length of the fish between 

 one third to one half the distance from the base of the dorsal 

 fin and the midlateral septum. The incision ran from the skull 

 to beneath the segmented-ray portion of the dorsal fin. The 

 skin was either removed or folded dorsally to expose the 

 underlying muscle. The inclinatores dorsales usually lifted up 

 with the skin, or were removed individually to permit exami- 

 nation of the epaxial muscles and the dorsal portions of the 

 pterygiophores. When appropriate, epaxial fibres were 

 traced anteriorly or posteriorly to ascertain their association 

 with the supracarinalis muscle system. The insertions of 

 epaxial fibres to pterygiophores were often re-examined on 

 cleared and stained specimens and dry skeletons in the 

 collections of the American Museum of Natural History, 

 Milwaukee Public Museum, National Museum of Natural 

 History, and The Natural History Museum. These specimens 

 are not listed in Table 1. Illustrations of muscles were made 

 with a camera lucida attached to a binocular dissecting 

 microscope. 



Material dissected for myological observations is listed in 

 Table 1. All species examined during the study are repre- 

 sented in this list, although in many cases, multiple specimens 

 were examined, occasionally from different lots, and some- 

 times from museum collections other than those listed, par- 

 ticularly the Field Museum of Natural History and Royal 

 Ontario Museum. A complete list can be provided by the 

 authors. Institutional codes follow Leviton et al. (1985). 



RESULTS 



Many (if not most) fishes have some epaxial fibre insertion 

 near the proximal ends or near the middle of the dorsal-fin 

 pterygiophores, whereas some taxa have epaxial muscle 

 insertions on to the distal ends of the pterygiophores. We 

 recognize four morphotypes of epaxial musculature, Types 

 to 3. The consecutive numbering of the morphological types 

 is not meant to imply character transformations; the morpho- 

 types do not necessarily form a polarized transformation 

 series. The vast majority of acanthomorph fishes (including 

 putative basal taxa) exhibit an apparently primitive condition 

 of the epaxial muscles, Type 0, with no attachment to the 

 distal parts of the dorsal-fin pterygiophores, and with the 

 musculature usually lying well below the dorsal tips of the 

 pterygiophores (Fig. 1; Table 1). 



Of those taxa that do exhibit insertions on to the distal 

 portions of the pterygiophores, epaxial fibres rarely insert on 

 to pterygiophores other than those bearing non-segmented 

 rays (spines), except where these ray elements are inter- 

 preted as secondarily derived from spines (e.g., pseudochro- 

 mids, zoarcoids, pleuronectiforms). In one scorpaeniform 

 and a perciform genus as discussed below, and probably the 

 paracanthopterygian Opsanus beta, there is insertion on 

 primary ray-bearing pterygiophores. Among the taxa with 

 dorsal insertions of epaxial fibres to spine-bearing pterygio- 

 phores, there are three recognizable morphologies. Although 

 these morphologies can be defined by specific taxa, their 



apparent differences become somewhat subjective at the ends 

 of their respective morphological spectra. 



Type 1 is characterized by a partially separate muscle mass 

 or series of slips of muscle fibres that insert on to the 

 dorsoposterior and dorsolateral processes of the proximal- 

 middle and/or distal radials of the pterygiophores. At least 

 some fibres originate from the main body of epaxial muscle, 

 but in extreme cases the dorsal muscle mass is detached 

 between successive myosepta, and anteriorly there can be an 

 elongate separate slip of muscle to an anterior pterygiophore 

 (Fig. 2). We observed this morphotype in a single paracan- 

 thopterygian species {Opsanus beta) (Fig. 3), blennioids, 

 most cirrhitoids, seven percoid families (Apogonidae, Cen- 

 trogeniidae, Centropomidae, Grammatidae, Haemulidae, 

 Percidae, and Serranidae) and two trachinoid families 

 (Champsodontidae and Cheimarrhichthyidae) among the sur- 

 veyed perciforms (Figs 1, 4-5, 12-17), and all but one 

 examined scorpaeniform (Figs 6-8) (Table 1). 



Among examined scorpaeniforms with Type 1, Normanich- 

 thys crocked exhibits a unique morphology (Fig. 8). The 

 epaxial muscles insert on to the lateral processes of the first 

 nine or ten pterygiophores as a separate mass of muscle. 

 Posterior to the first dorsal fin, epaxial fibres attach directly 

 to spineless (naked) pterygiophores and these fibres are not 

 arranged as a separate muscle mass. A separate muscle mass 

 is also present at the second dorsal fin, with insertions on to 

 those pterygiophores bearing segmented rays. This gradually 

 tapers out posteriorly and merges with the main body of 

 epaxial muscle. Other scorpaeniform and percoid taxa exhib- 

 iting Type 1 are quite consistent in their epaxial morphology; 

 even among unusual taxa such as Aploactis (a scorpaeni- 

 form), which has its dorsal fin placed far anteriorly over the 

 skull, a narrow tendon extends from the epaxial to insert on 

 to the third dorsal-fin pterygiophore. Differences arise in the 

 degree of muscle separation, size of the anterior slip, on to 

 which pterygiophores the muscle inserts, and on to which 

 radials of the pterygiophores the insertion occurs (cf. Figs 

 2-8). 



Species with a Type 2 epaxial morphology lack the obvious 

 separation of the dorsal muscle bundle that inserts on to the 

 distal portions of the pterygiophores, and the anterior slip is 

 always absent. The insertions resemble sheets hanging on a 

 clothes-line, draping from one pterygiophore to the next (Fig. 

 9). In some taxa, the insertions are primarily via long 

 tendons, and the muscle fibres themselves are relatively 

 distant from the dorsal parts of the pterygiophores (Fig. 10). 

 In most elongate taxa, the muscles are much more dorsally 

 situated and the tendons are not as obvious. This morphology 

 is found in various perciform taxa, including some members 

 of the Cirrhitidae, Labridae, Percoidei, and Trachinoidei, 

 and all of the few examined members of the Callionymoidei, 

 Notothenioidei and Zoarcoidei (Table 1). The Tetraodonti- 

 formes have a modified condition of this basic morphology 

 which will be discussed below. 



A Type 3 epaxial morphology was found only in the family 

 Mullidae (Fig. 11; Table 1). This type consists of a few 

 epaxial fibres inserting on to an anterior pterygiophore 

 relatively ventrally and on to a lateral wing along the main 

 shaft rather than on to a dorsal posterolateral process. A 

 completely separate slip of muscle sits dorsal to the epaxial 

 muscle and inserts on to the anterior pterygiophore and only 

 the posterior pterygiophores of the first dorsal fin. It extends 

 further posteriorly, inserting on to the first pterygiophore of 

 the second dorsal, and gradually narrows posteriorly, insert- 



