AHLSTROM ET AL.: GONOSTOMATIDAE, STERNOPTYCHIDAE 



195 



Fig. 102. Cydothone signata 9.0 mm SL, drawn by H. Orr. 



and Type Gamma, as being more specialized. This recognition, 

 although not stated by these authors, is based on a concept that 

 Types Alpha and Gamma photophores of some stomiiformes 

 appear to be elaborations of Type Beta photophores. In other 

 words, their particular features appear to be developmental ter- 

 minal additions to Type Beta photophores and are therefore 

 available for use as synapomorphies for stomiiform subgroups. 

 Although more detailed analyses of these features are needed, 

 for the sake of discussion we here accept that Type Beta pho- 

 tophores are primitive for stomiiforms. 



Weitzman (1974:338), on the basis of outgroup comparison 

 (not described or discussed in his text), considered four proximal 

 pectoral-fin radials to be primitive for stomiiforms, their re- 

 duction to three or fewer to be specialized. We see no reason 

 to change that analysis. Thus three or fewer proximal pectoral- 

 fin radials are available as synapomorphous characters for sto- 

 miiform subgroups. 



Ahlstrom ( 1 974:660) described what can be labeled as "white" 

 photophore development in which most, or at least the ventral 

 series of photophores, are "laid down initially during a white 

 photophore stage [before black pigment develops] and only a 

 few photophores are late forming." One form or another of 

 "white" photophore development is common to all stomiiforms 

 except those including the gonostomatid genera Bonapariia. 

 Margrethia. and Gonostoma, and the stemoptychids of Weitz- 

 man ( 1 974). Members of these gonostomatid and stemoptychid 

 genera have a protracted metamorphosis from the larval stage 

 as well as a gradual, more extended photophore formation. This 

 latter type of photophore development appears to be an elab- 

 oration of "white" photophore development and thus we con- 

 sider white photophore development primitive with respect to 

 the more complicated forms having prolonged photophore de- 

 velopment. Again, much information of an anatomical and de- 

 velopmental nature remains to be gathered from the process of 

 photophore development. 



If "white" photophore development and Type Beta photo- 

 phores are primitive in regard to stomiiform subgroups and 

 therefore unavailable as synapomorphies for stomiiform 

 subgroups, then the conflict regarding the distribution of char- 

 acters among taxa between Ahlstrom (1974) and Weitzman 

 (1974) disappears in a phylogenetic analysis by somewhat al- 

 tering certain of the groups of both authors as follows. 



In our tentative scheme of relationships, Weitzman's Ster- 

 noptychidae and Ahlstrom's Group (2) genera (Ahlstrom, 1 974: 

 671), Bonapariia, Margrethia, and Gonostoma, the Gonosto- 

 matidae in the strictest sense, are united by a synapomorphy 

 consisting of a specialized form of prolonged metamorphosis 



and photophore development described by Ahlstrom (1974: 

 660-661). See also Tables 52-54 herein. These three gonosto- 

 matid genera and Cydothone apparently share derived char- 

 acters of the jaws and associated head parts which will be ex- 

 plained in a later contribution. These four genera retain the 

 primitive Type Beta photophores, a character relating stomi- 

 iforms only at the ordinal level. In our opinion these four genera 

 constitute the Gonostomatidae and Cydothone may have lost 

 prolonged photophore development through paedomorphic re- 

 versal associated with the small size of most of its members, a 

 situation needing further study. 



The Stemoptychidae have specialized Type Alpha photo- 

 phores and the several other synapomorphies listed by Weitz- 

 man ( 1 974:446-448). In addition they apparently share a unique 

 photophore growth pattern previously unrecorded. One of us 

 (Weitzman) has been studying photophore development in re- 

 lation to phylogenetic studies in stomiiforms and has found that 

 each cluster or group of photophores of the stemoptychids ap- 

 pears to develop by budding from one single photophore rather 

 than by fusion at a later growth stage of separately developed 

 photophores. This is a terminal developmental addition in pho- 

 tophore ontogeny and both outgroup comparison and devel- 

 opmental information indicate that this pattern of photophore 

 formation is a specialization in comparison to the simpler ap- 

 pearance of single, separate body photophores (usually one per 

 scale in any given series found in other stomiiforms). This growth 

 character appears to be present in all stemoptychid genera for 

 which we have developmental information. It is therefore a 

 likely synapomorphy for the group. 



Manducus (based on the type species, Gonostoma maderense 

 Johnson) is a primitive stomiiform, having ordinal-level char- 

 acters with no known specialized characters except the absence 

 of an adipose fin and a short neural spine on the preural centmm. 

 The latter may be a primitive rather than a specialized stomi- 

 iform feature. Diplophos (based on the type species Diplophos 

 taenia Gunther) appears to have a transitional stage pectoral 

 radial morphology between Manducus on the one hand and the 

 Photichthyidae of Weitzman (1974) (an ill-defined group) and 

 the Stomiidae on the other. In Manducus the cartilages and 

 bones of proximal pectoral-fin radials III and IV remain separate 

 whereas Diplophos has the cartilages, but not the bones, of the 

 two elements fused. Fink and Weitzman (1982:65-67). In the 

 "photichthyids" and stomiids the cartilages and bones of the 

 two medial pectoral-fin radials are fused. This represents the 

 terminal condition in the transition series except that in some 

 genera there is a reversal of radial numbers and in Eustomias 

 there occurs a further specialized, reduced pectoral-fin radial 



