Cooper and Chapleau: Monophyly and intrarelationships of the family Pleuronectidae 
707 
Distribution of these states within other pleuro- 
nectid taxa indicates a degree of homoplasy for these 
characters but does not refute the monophyly of 
Hippoglossoidinae. The supraoccipital plate is also 
absent in Microstom us (Microstomini). Pterosphenoid 
and prootic of the blind side are also united to form 
the dorsal margin of the anterior prootic foramen in 
Verasper variegatus and in most species of the 
Pleuronectinae. Reduction of the blind-side ptero- 
sphenoid is also observed in Pleuronichthys (Micro- 
stomini) and may be a reversal within the Pleuro- 
nectidae. Two rows of uniform teeth are also present 
in Dexistes rikuzenius (Microstomini) and the 
Pleuronectini. 
Intrarelationships of Hippoglossoidinae 
Genus Acanthopsetta A. nadeshnyi is the sister 
species to Cleisthenes and Hippoglossoides (Fig. 14). 
Placement of A. nadeshnyi as a distinct lineage 
within Hippoglossoidinae is supported by two struc- 
tures not present in other Hippoglossoidinae: sen- 
sory canal on ocular-side preorbital present (2); and 
presence of scales on eye surfaces (45). The presence 
of a sensory canal on the ocular-side preorbital is a 
reversal for the family that also occurs in Rein- 
hardtius hippoglossoides . Scales present on the sur- 
face of each eye have a more homoplastic distribu- 
tion as they are found in Reinhardtius stomias, 
Lyopsetta exilis, Dexistes rikuzenius, Glyptocephalus 
kitaharai, and Microstomus. 
The sister relationship between Cleisthenes and 
Hippoglossoides is supported by three synapo- 
morphies (Fig. 14): ocular-side supratemporal jointed 
at anterior end of bifurcation (43, Fig. 13B); nasal 
bones of the blind side are absent ( 50 ); and more than 
seven infraorbital bones on ocular side (51). 
These morphological states are not unique within 
the family. The bifurcation of the supratemporal is 
observed in Lyopsetta exilis on both ocular and blind 
side, but not all species of Cleisthenes and Hippo- 
glossoides have the supratemporal bifurcation on the 
blind side. The absence of nasal bones on the blind 
side and number of infraorbitals are shared with 
some species in the Pleuronectinae, the latter being 
also observed in Hippoglossus stenolepis. 
Genus Cleisthenes This genus contains two spe- 
cies, C. herzensteini and C. pinetorum, and is diag- 
nosed by four synapomorphies (Fig. 14): migrated eye 
is near dorsal midline (25); gill rakers on fourth 
epibranchial present (40); a double crest or groove 
present on supraoccipital and blind-side frontal (38, 
Fig. 10, C-E); and crest extending from supraoccipi- 
tal to blind side reduced (52, Fig. 10, D and E). 
These morphological characters are distributed 
within other pleuronectid taxa but are not observed 
in any other Hippoglossoidinae. The position of the 
migrated eye is also observed in Reinhardtius . Pres- 
ence of gill rakers on the fourth epibranchial has a 
limited distribution in Eopsetta grigorjewi, E. 
jordani, and Psettichthys melanostictus. The double 
crest on the supraoccipital and blind-side frontal is 
recurrent throughout the family but unique within 
Hippoglossoidinae. The reduced crest on the blind- 
side frontal is also observed in Reinhardtius stomias, 
Pleuronichthys verticalis, and Pleuronectini. 
Genus Hippoglossoides This genus contains 4 
species: H. dubius (not examined), H. elassodon, H. 
platessoides, and H. robustus, defined by two 
synapomorphies (Fig. 14). The structure of the ante- 
rior margin of the mesethmoid is complex but con- 
sistent in Hippoglossoides . In this genus, the “thin 
plate” structure of the mesethmoid (53, Fig. 8B) is 
distinct in relation to other members of Hippo- 
glossoidinae who have a thickened triangular-shaped 
mesethmoid (Fig. 8C), or the plesiomorphic structure 
of an open canal found in Cleisthenes pinetorum (Fig. 
8A). In addition, there are 12 to 14 abdominal verte- 
brae (23), an increase from 11 or fewer in other taxa. 
The interrelationships within Hippoglossoides are 
not fully resolved by this analysis. Hippoglossoides 
dubius has 13 abdominal vertebrae (Norman, 1934; 
Sakamoto, 1984a) and is assumed to have common 
ancestry with other species of Hippoglossoides . 
Subfamily Pleuronectinae 
The Pleuronectinae is the largest subfamily within 
the Pleuronectidae with 40 species (38 examined in 
