FINK: STOMIIFORMS 



183 



My hypotheses are based on a study of 330 characters, mostly 

 taken from the skeleton, but with some from the head muscles, 

 photophores, and other parts of the soft anatomy. The conclu- 

 sions are presented in Fig. 97. Traditional families are not rec- 

 ognizable in this scheme of relationships. 



Evidence for the arrangement of the genera is presented else- 

 where (Fink, in prep.), but some characters will be discussed 

 below, particularly those relevant to some of the larger portions 

 of the tree or in areas that might seem controversial to some 

 readers. For ease of communication, I will state here that my 

 choice of classification for this group is an expansion of the 

 traditional Stomiidae of Regan and Trewavas (see Fig. 97). 



Monophyly of the Stomiidae is established on the basis of up 

 to 1 7 characters, including 1 ) presence of a mental barbel, 2) 5 

 hypurals in the caudal skeleton rather than 6, 3) lack of gill 

 rakers in adults, 4) a divided geniohyoideus muscle, and 5) a 

 portion of the adductor mandibulae inserting on the postorbital 

 photophore. 



The Astronesthidae, as most recently discussed by Weitzman 

 (1967), consisted oi Astronesthes. Boroslomias. Heterophotus. 

 Neoncsthcs, and Rhadinesthes. As can be seen in Fig. 97, the 

 group is clearly not monophyletic. Neonesthes is the sister group 

 of all other stomiids, a hypothesis borne out by many characters 

 shared by the remaining stomiid genera, including lack of tooth- 

 plates on basibranchial 1, epibranchial 4, and on the posterior 

 edges of gill arches 1-4, and presence of rector muscles attaching 

 to the fifth ceratobranchial. The several equally parsimonious 

 constructions of stomiid relationships leave an unresolved tri- 

 chotomy at the next level, there being insufficient evidence re- 

 garding the positions of Aslronesthes. Boroslomias. and the re- 

 maining stomiids. This problem will be further discussed by 

 Fink (in prep.). 



The remaining stomiids are united by such traits as lack of 

 toothplates on basibranchial 3 and position of the basihyal- 

 hypohyal ligament, as well as specializations of the dorsal and 

 anal fin skeletons. At this point there lies another unresolved 

 trichotomy, involving the groups Heterophotus plus Rhadi- 

 nesthes, Slomias plus Chauliodus, and the remaining stomiids. 

 Heterophotus and Rhadinesthes are documented as sister taxa 

 by several characters, including an elongate dorsal spine on the 

 cleithrum and a preopercle that is narrow at the area of the 

 symplectic-hyomandibular joint. That Chauliodus and Stomias 

 are sister taxa is supported by numerous characters, including 

 a nasal bone which forms a cup-like wall to the nasal capsule; 

 distribution of the palatine teeth into two areas, one anterior 

 and one well posterior; branchiostegals deeply bifurcated dor- 

 sally; and a distinct hexagonal pigment pattern in the skin. I do 

 not recognize the genus Macrostomias since work in progress 

 shows that those species are the sister group to a derived group 

 within Stomias. 



The remaining genera, comprising the traditional families 

 Melanostomiidae. Malacosteidae, and Idiacanthidae, are united 

 by presence of many features, including no more than one pair 

 of toothplates associated with any basibranchial ossification, 

 and reduction of the distal radials of the pectoral fins. 



As postulated by Regan and Trewavas (1930), I have also 

 found that Chirostomias and Tngonolampa are sister taxa based 

 on features such as fusion of the bilateral toothplates of basi- 

 branchials 2 and 3 and reduction of the supramaxiUa to a sliver 

 of bone. These genera are the sister group to the remaining 

 genera, a hypothesis supported by several characters, including 

 fewer than 6 branchiostegals articulating with the posterior cer- 



Neonesthes 



astronesthes 



borostomias 



Heterophotus 



Rhadinesthes 



Chauliodus 



Stomias 



Chirostomias 



Trigonolampa 



Thysanactis 



leptostomias 



Opostomias 



Odontostomias 



Flagellostomias 



Photonectes 



Echiostoma 



Melanostomias 



Idiacanthus 



Tactostoma 



Grammatostomias 



Bathophilus 



eustomias 



Aristostomias 



Malacosteus 



Pachystomias 



Photostohias 



Fig. 97. Hypothesis of relationships within the Stomiidae, as dis- 

 cussed herein. 



atohyal ossification, 3 or fewer distal pectoral fin radials, and 

 presence of a modification of the anterior pectoral fin rays into 

 a structure I call the "rod-ray complex." 



For the remaining genera, I will concentrate on establishing 

 the major lineages as monophyletic and on areas that affect 

 traditional familial classifications of the group, particularly the 

 relationships of the "malacosteids" and Idiacanthus. 



One monophyletic group is comprised of Flagellostomias. 

 Leptostomias. Odontostomias. Opostomias. and Thysanactis. 

 Among the diagnostic features are fusion of the distal cartila- 

 ginous tips of the lateral ethmoid and supraethmoid, and an 

 elongate opercular process of the hyomandibula. 



The remaining genera are supported as monophyletic by nu- 

 merous characters, among them being lack of a retroarticular 

 (also lacking in Trigonolampa), and the form of the articulation 

 of the interhyal. The latter element articulates anterior to the 

 front margin of the cartilage between the hyomandibula and 

 symplectic and is bound to the metapterygoid by a ligament 

 from the anterior margin of the interhyal. 



The Malacosteidae has traditionally been comprised of three 

 genera, Aristostomias. Malacosteus. and Photostomias, all of 

 which lack a floor to the mouth. The evidence shows that Pachy- 



