Cooper and Chapleau: Monophyly and intrarelationships of the family Pleuronectidae 
715 
Pleuronectidae but is not observed in Pseudo- 
pleuronectes, Pleuronectes platessus, and P. quadri- 
tuberculatus. The three alternatives are equally rep- 
resented in 48 (37.5%) of the most parsimonious re- 
sults but are not illustrated in the 50% majority-rule 
consensus tree (Fig. 1). All three alternatives (Fig. 
18) maintain monophyly for Platichthys, Pleuro- 
nectes , and Pseudopleuronectes, individually. These 
alternatives place some or all species of Limanda as 
paraphyletic within a Platichthys , Pleuronectes, 
Pseudopleuronectes clade but do not exclude any spe- 
cies of Platichthys , Pleuronectes, and Pseudo- 
pleuronectes. Character states in support of these 
conflicting nodes illustrate homoplasy observed in 
Limanda (Fig. 18, A-C). Some or all species of 
Limanda are observed to share these character states 
with the other three genera. However, most of the 
exceptions and homoplasy observed in these struc- 
tures fail to illustrate an evolutionary hypothesis that 
is more convincingly corroborated than the topology 
presented in the consensus tree (Fig. 1). 
The fourth lineage unites Pleuronectes and 
Pseudopleuronectes . This clade was observed in 75% 
of the equally parsimonious trees (Fig. 1) and is sup- 
ported by four synapomorphies (Fig. 17): less than 
six teeth on ocular-side maxilla (66, Fig. 9D); teeth 
incisorlike (70, Fig. 9D); teeth forming a continuous 
cutting edge (16, Fig. 9D); and dorsoposterior pro- 
cess of dentary similar in size on both ocular and 
blind sides (65, Fig. 9D), a reversal of the second lin- 
eage of Pleuronectinae. 
Homoplasy observed in these morphological char- 
acters reveals a pattern of parallel evolution between 
this lineage and the clade formed by Glyptocephalus, 
Microstomus, and Pleuronichthys (Microstomini). 
Less than six teeth on the ocular-side premaxilla are 
also present in these three genera of Microstomini. 
The presence of incisorlike teeth is also observed in 
Parophrys vetula as well as Glyptocephalus and Mi- 
crostomus. A continuous cutting edge found on the 
teeth has independently evolved in Glyptocephalus 
and Microstomus. The symmetrically sized dorso- 
posterior process of the dentary is not observed in 
Pseudopleuronectes herzensteini, Pleuronectes platessus, 
and P. quadrituberculatus and is a reversal that is par- 
alleled in Glyptocephalus and Microstomus. 
Alternative topologies observed in 32 of 128 (25%) 
trees unite either a monophyletic or paraphyletic 
Pleuronectes with Platichthys (Fig. 18, C and D). In 
Pleuronectes and Platichthys the mesethmoid has a 
thickened, triangular anterior margin (53, Fig. 80. 
The fifth ceratobranchial has a strong medial curve 
forming a triangular plate (71, Fig. 3D). The teeth of 
the fifth ceratobranchial are in multiple rows (49, 
Fig. 3D), and these teeth are generally rounded or 
molariform (72, Fig. 3D). Three of these characters 
(49, 53, 71) are used to define the third lineage of 
Pleuronectini but notably exclude Pseudopleuro- 
nectes. The molariform teeth on the fifth cerato- 
branchial (72, Fig. 3D) are observed in Pleuronectes 
and only in Platichthys bicoloratus. The alternative 
hypothesis, indicating a sister relationship between 
Pleuronectes and Platichthys, has the same charac- 
ter support as the hypothesis presented in the con- 
sensus tree. However, this topology is parsimonious 
in only 32 trees and only in conjunction with one of 
the two alternatives that either position a para- 
phyletic Limanda after Pseudopleuronectes (Fig. 180 
or hypothesize a paraphyletic Pleuronectes (Fig. 18D). 
Support for either of these topologies is not well cor- 
roborated. Therefore, alternatives to the consensus 
tree are not as robust to the homoplasy observed in 
the analysis. 
Genus Limanda Monophyly and intrarelation- 
ships of Limanda are unresolved by this analysis 
owing to homoplasy observed in these six species (Fig. 
17). Limanda punctatissima and L. proboscidea are 
the only two pleuronectid species with bony promi- 
nences of the postocular ridge extending anteriorly 
onto the interorbital bar (103, Fig. 10E). Limanda 
aspera and L. ferruginea are united by three mor- 
phological characters: the supraoccipital crest not 
forming a groove for the dorsal-fin pterygiophores 
(38, Fig. 10, A and B); blind-side metapterygoid not 
articulated with entopterygoid (34, Fig. 2A), both 
reversals in Pleuronectini; and supratemporal of the 
blind side jointed at its anterior bifurcation (44, Fig. 
13B). This character state has evolved independently 
five times in Pleuronectidae as it is also observed in 
Cleisthenes herzensteini, Hippoglossoides elassodon, 
Lyopsetta exilis, and Reinhardtius hippoglossoides. 
Limanda limanda and L. sakhalinensis are mono- 
phyletic in 75% of the trees (Fig. 1). Two character 
states unite these species: first epibranchial is bi- 
furcated ( 12, Fig. 3A); and bony prominences on ocu- 
lar-side postocular ridge absent (101). Both of these 
characters are reversals also observed in Limanda 
aspera. Alternative topologies observed in 32 (25%) 
other trees, place Limanda sakhalinensis and L. 
limanda as paraphyletic taxa in the tribe or as 
paraphyletic within a clade that unites these two spe- 
cies with Limanda punctatissima and L. proboscidea . 
Although the species of Limanda are not resolved 
as a monophyletic group, they are distinguishable 
from other members of Pleuronectini. They have re- 
duced dentition on the ocular side but maintain more 
than six teeth, where as other species of Pleuronectini 
generally have six or fewer (Norman, 1934). The teeth 
are bluntly conical or pointed with truncated tips, 
whereas all other members of this tribe have com- 
