Cooper and Chapleau: Monophyly and intrarelationships of the family Pleuronectidae 
709 
cephalus cynoglossus, G. stelleri, G. zachirus, and 
Pleuronichthys guttulatus. However, the blind-side 
pterosphenoid and prootic uniting to form the dorsal 
margin of the anterior prootic foramen is homoplas- 
tic in Hippoglossoidinae and Verasper variegatus 
(Hippoglossinae). The medial curvature of the fifth 
ceratobranchial is not observed in Microstomus, 
Glyptocephalus, and Pleuronichthys, and teeth on the 
fifth ceratobranchial are sharply pointed in Micros- 
tomus bathybius, Pleuronichthys , and Lepidopsetta. 
Tribe Isopsettini Genus Isopsetta The tribe 
Isopsettini is monotypic with Isopsetta isolepis. Four 
character transformations identify the lineage (Fig. 
6): blind-side metapterygoid is not articulated with 
entopterygoid (34, Fig. 2A); anterior margin of 
mesethmoid forming an open canal (53, Fig. 8A); 
haemal spines of anteriormost caudal vertebrae 
broadly attached to centrum (73, Fig. 5B); and 
epiotics are sutured along dorsal posterior margin of 
skull (74). 
Three of these four character states are reversals 
within the Pleuronectinae. The absence of an articu- 
lation between the blind-side metapterygoid and 
entopterygoid is a reversal of the structure observed 
in the Psettichthyini and in most species of 
Microstomini and Pleuronectini, except Lepidopsetta, 
Pleuronichthys guttulatus, Limanda aspera, and L. 
ferruginea. The open canal on the anterior margin of 
the mesethmoid is a reversal that is also observed in 
the pleuronectines, Glyptocephalus, Microstomus, 
and Pleuronichthys (except P. verticalis), and in 
Cleisthenes pinetorum (Hippoglossoidinae). Epiotics 
sutured along the dorsal posterior margin are ob- 
served only in one other pleuronectid species, Mi- 
crostomus pacificus , and the broad attachment of 
haemal spines to the anteriormost caudal vertebrae 
is a reversal recurrent throughout the family, indi- 
cating a homoplastic structure with a complex dis- 
tribution. Despite the reversals noted for this lin- 
eage, placement of Isopsettini within Pleuronectinae 
is supported by the eight synapomorphies for Pleuro- 
nectinae and the 11 derived morphological charac- 
ters for the second lineage in Pleuronectinae. 
Tribe Microstomini The tribe Microstomini con- 
tains 19 species (17 examined) classified in five gen- 
era: Lepidopsetta, Dexistes, Pleuronichthys, Glypto- 
cephalus, and Microstomus (Fig. 15). Although the 
placement of this tribe within the Pleuronectinae is 
supported by 25 character transformations presented 
for monophyly and intrarelationships of the subfam- 
ily, the status of this tribe, as well as its intra- 
relationships, are determined mostly by character 
reversals. The monophyly of this tribe is character- 
ized by four character transformations. All are re- 
versals within the Pleuronectinae (Fig. 6): suture 
between mesethmoid and blind-side prefrontal is ei- 
ther incomplete or complete with a small foramen 
present (14, Fig. 8, A-C); single crest on supraoccipi- 
tal (38, Fig. 10, A and B); lower jaw with multiple 
rows of teeth (41); and reduced or absent process on 
dorsoposterior edge of epiotics (68, Fig. 10, A-C). 
The few exceptions to the distribution of these 
states within Microstomini and the occurrence of 
these same reversals outside of Microstomini indi- 
cate the homoplastic nature of these structures. 
Multiple rows of teeth on the lower jaw were not ob- 
served in Microstomus and Glyptocephalus, which is 
homoplastic within Hippoglossinae and recurrent for 
basal lineages within the family but which has only 
this one instance of reversal in Pleuronectinae. The 
absence or reduction of an epiotic crest is a reversal 
also found in Pseudopleuronectes herzensteini and P. 
yokohamae . 
Intrarelationships of Microstomini Three lineages 
of Microstomini are defined by 16 character trans- 
formations; ten are reversals (Fig. 15). 
Genus Lepidopsetta The first lineage of Micro- 
stomini, consists of Lepidopsetta containing two spe- 
cies, L. bilineata and L. mochigarei (Fig. 15). This ge- 
nus is diagnosed by the presence of demersal eggs (75), 
a feature observed in only four other pleuronectid spe- 
cies: Pseudopleuronectes americanus, P. schrenki, P. 
yokohamae , and P. obscurus (not examined). 
The second lineage indicates common descent for 
Dexistes, Pleuronichthys, Microstomus, and Glypto- 
cephalus. Four character states unite these genera 
(Fig. 15): first epibranchial bifurcated at distal end 
(12, Fig. 3A); cardiac apophysis simple at tip with a 
bifurcation positioned anteriorly (39, Fig. 12, E and 
F), except in Pleuronichthys ocellatus and P. ritteri; 
intercalar not in contact with basioccipital (57, Fig. 
7B), a reversal in Pleuronectinae; and less than seven 
teeth on ocular-side premaxilla (66). 
Exceptions to character states within the second 
lineage of Microstomini were not congruent and did 
not provide alternative topologies that either ex- 
cluded taxa observed to be exceptions to this distri- 
bution or included taxa that were homoplastic with 
these structures. Bifurcation of the first epibranchial 
is a reversal in the Pleuronectidae. Shape of the car- 
diac apophysis of the urohyal was observed only in 
one other pleuronectid, Limanda aspera. The 
intercalar is in contact with the basioccipital in 
Glyptocephalus cynoglossus (57, Fig. 7C). The reduc- 
tion of teeth on the ocular-side premaxilla (less than 
7) is not observed in Pleuronichthys guttulatus and 
Glyptocephalus. In Glyptocephalus , variation in tooth 
number on the ocular-side premaxilla ranged from 8 
to 16 in G. zachirus, but in all species there is a 
