PAXTON ET AL.: MYCTOPHIDAE 



Table 64. Extended. 



243 



some acanthopterygians. Although it could be argued that the 

 short gut that lengthens during development in a few forms of 

 myctophids represents the primitive condition, we consider the 

 primitive myctophid condition a moderate— iengthed gut, with 

 different derived states, short and long. (26) Although the caudal 

 luminous organs are sexually dimorphic in about half the genera, 

 we assume the original caudal organs were not sexually dimor- 

 phic. (27) No photophores are present on the described larvae 

 of Neoscopelus. However the Br, develops in all larval mycto- 

 phids except Taamngichthys and Notolychmis. and its univer- 

 sality indicates it was present in the ancestral myctophid. Other 

 larval photophores however are present in fewer than half of 

 the genera and we consider their presence derived. (30) The 

 strongly developed caudal luminous organs found in Lampa- 

 dena and Taaningichthys are clearly a more specialized state 

 than the relatively unstructured organs found in many other 

 genera. (34) See the discussion of character 17. (36) Although a 

 strongly angled set of SAOs represents a linear position for the 

 first two photophores, we consider this condition developed by 

 the SAO, rising from a lower position in the weakly angled, 

 plesiomorphic position. (59) We consider the absence of a keel 

 or ridge on the fifth circumorbital of Hintonia to be secondarily 

 derived through loss. This is the only character state we have 

 used which is not present in all examined members of the line 

 it defines. 



We have thus attempted to determine polarity for 25 osteo- 

 logical, 17 larval and 17 photophore characters. We initially 

 attempted a phylogenetic analysis utilizing the distribution of 

 23 larval characters at the species level. The resulting diagram 

 split some genera into as many as three unrelated lines. We 

 remain convinced that the myctophid genera as currently de- 

 fined by larval morph, photophore pattern and osteology rep- 

 resent monophyletic lines (even though such genera as Diaphus, 

 Lampanyctus, Myctophum and Hygophum may be formally di- 

 vided as subgenera or genera by future work). These genera we 

 use as the starting point in the present study. We have con- 

 structed a phylogenetic tree (Figs. 1 25, 1 26) based on our knowl- 

 edge of the family and used the apomorphic states of the 59 

 characters to define the various branching points, which is the 

 basis of the following discussion. 



The subfamily Lampanyctinae is defined by two apomorphies 

 restricted to all members of the subfamily (those characters 

 found in all members of a lineage and nowhere else in the family 

 are underlined in Figs. 125 and 126). the presence of a cleithral 

 shelf and a single, fused extrascapular. The subfamily Mycto- 

 phinae is defined by two apomorphies, short or moderate jaws 

 and narrow larval eyes, but these features are also found in a 

 few genera of the Lampanyctinae. The number of Pre photo- 

 phores defines all members of one of the subfamilies (see dis- 

 cussion of character 4 above). 



