680 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



HY5 



_THC + HY2-4 



HY 5 



THC + HY 1 



Fig. 363. Caudal skeleton of Tephnnectes sinensis. Hypural pattern 

 1 (upper); caudal skeleton of Tnnectes fimbhata. Hypural pattern 3 

 (middle); and caudal skeleton of Rhombosolea pleheia. Hypural pattern 

 4 (lower). Abbreviations as in Fig. 359. "V" on distal end of fin ray 

 indicates dorsal- and ventralmost branched ray. 



used as evidence that soleids and cynoglossids are most closely 

 related are plesiomorphic for the order (symmetrical nasal or- 

 gans, dimorphic optic chiasmata), found in some pleuronectoids 

 but dismissed as parallelisms [lower jaw not prominent, absence 



of postcleithra, several "soleoid characters" found in rhombo- 

 soleines, (see Norman, 1934)], or are incorrect (absence of all 

 ribs). Other states used to unite the soleoid families include; (1) 

 a preopercular margin covered by skin and scales; and (2) skin 

 covering the dentary and interopercular bones being continuous 

 across the chin, hiding the isthmus and branchioslegal rays (Nor- 

 man, 1966). A covered preopercular margin is not limited to 

 soleoids; it occurs in some rhombosoleine genera (Chabanaud, 

 1949; Hensley, pers. observ.). The second state as well as the 

 absence of pleural ribs are possible synapomorphies for the 

 group. 



Cynoglossidae.—lhtrt is little doubt that the tonguesoles are 

 monophyletic. They are unique in having the ventral fin of the 

 blind side oriented along the midventral line and the ocular fin 

 placed more dorsally or missing. The relationship of this family 

 to other groups, however, is obscure (see Soleidae). 



Soleidae.—The main character state proposed as uniting the 

 two soleid subfamilies (Soleinae, Achirinae) appears to be that 

 all species are dextral. This is still a poorly known group, and 

 we are not prepared to make much of a contribution here. How- 

 ever, there are some marked differences between these subfam- 

 ilies. In several characters, the Achirinae are more primitive 

 than originally thought. Some species have hypural pattern 1 , 

 the most primitive. In species where hypural fusions have oc- 

 curred, the first hypural remains free and articulates with the 

 terminal half centrum (Fig. 363 middle). The haemal spine of 

 the second preural centrum is autogenous (i.e., the plesiomorph- 

 ic state for the order) in achirines. Uroneurals may still be pres- 

 ent in some species. Although postcleithra are lacking in adult 

 soleoids, at least one achirine species has them during larval 

 development (Futch et al., 1972). Soleines differ from achirines 

 in these characters in that they show what appear to be more 

 derived states. The Soleinae have hypurals 1-4 fused to the 

 terminal half centrum (Fig. 362F), the haemal spine of the sec- 

 ond preural centrum is attached, there is no indication of uro- 

 neurals, and postcleithra have not been reported in larvae or 

 adults. Soleines share these states with the Cynoglossidae. In 

 addition, both groups have vertebral transverse apophyses, which 

 are missing in achirines. The possibilities that the Soleidae are 

 not monophyletic and the Soleinae are more closely related to 

 the Cynoglossidae should be more thoroughly explored. 



Pleuronectoidei. — Some of the character states used to define 

 this group are plesiomorphic for the order: (1) preoperculum 

 with free margin; (2) presence of postcleithra; and (3) presence 

 of pleural and epipleural ribs. Some apomorphic states for the 

 order are not limited to pleuronectoids; e.g., loss of dorsal and 

 anal spines. The Regan-Norman model has used the position 

 of the nasal organ of the blind side to separate pleuronectoids 

 from soleoids and psettodids. In pleuronectoids, this nasal organ 

 follows the migrating eye during metamorphosis. After meta- 

 morphosis, it remains near the dorsal edge of the head. This 

 was interpreted as a specialization of pleuronectoids, except that 

 this state does not occur in all Rhombosoleinae (i.e., nasal organs 

 remain symmetrically placed). Thus, it is not a synapomorphy 

 for the group, unless it can be shown that the nasal-organ sym- 

 metry in these rhombosoleines was secondarily derived from 

 the asymmetrical state. We have not done a survey of nasal- 

 organ symmetry, but incidental observations indicate that the 

 supposed differences between these states (i.e., symmetrical vs 



