Cooper and Chapfeau: Monophyly and intrarelationships of the family Pfeuronectidae 
705 
lar side (28, Fig. 2, B and C) also defines the lineage 
uniting Glyptocephalus, Microstomas, and Pleuro- 
nichthys within the Pleuronectinae. Absence or re- 
duction of gill rakers on first, second, and third 
epibranchials (29, 30, 31) is found to define basal lin- 
eages within the Pleuronectinae, whereas reduction 
of gill rakers on the first hypobranchial is observed in 
only some species of Pleuronichthys and Platichthys 
bicoloratus. 
Genus Hippoglossus This genus contains two 
species: II. hippoglossus and H. stenolepis and is 
monophyletic with three synapomorphies (Fig. 11): 
presence of subdivisions in hypural and parahypural 
plates, an autapomorphy for the genus (33); pres- 
ence of accessory processes on ventral margin of cau- 
dal vertebrae (7, Fig. 5A), a reversal for the family; 
and metapterygoid articulated with the blind-side 
entopterygoid (34, Fig. 2C). Only Microstomas 
bathybius and three species of Pleuronichthys have 
accessory processes on the caudal vertebrae. The 
metapterygoid is also articulated with the entop- 
terygoid of the blind side in Reinhardtius hippo- 
glossoides and species within Pleuronectinae. 
Genus Verasper This genus, containing V. mos- 
eri and V. variegatus is monophyletic with nine 
synapomorphies (Fig. 11): presence of a large fora- 
men between mesethmoid and blind-side prefrontal 
(35), autapomorphic for Verasper ; first epibranchial 
bifurcated (12); caudal fin is rounded (24), a reversal 
in this subfamily; gill rakers absent on both second 
and third epibranchials (30, 31); gill rakers reduced 
on second hypobranchial (36); sphenotic process not 
forming dorsal margin of hyomandibular socket (37, 
Fig. 7, B and C); groove present along supraoccipital 
crest for insertion of pterygiophores (38, Fig. 10, C- 
E); and cardiac apophysis of urohyal bifurcated (39, 
Fig. 120. 
Many character states found within Verasper are 
also observed in the Pleuronectinae, but the strength 
of the hypothesis placing Verasper within Hippo- 
glossinae exceeds the characters mentioned above 
and illustrates the convergent evolution of these 
structures. 
Genus Clidoderma C. asperrimum was not avail- 
able for analysis. This species has modified scales on 
the ocular side to form distinct bony tubercles very 
similar to those observed in Platichthys . However, 
this unique species appears to be more closely re- 
lated to Verasper than to Platich thys (Norman, 1934). 
This species has subsymmetrical jaws and a mix of 
pointed and bluntly conical teeth, not uniform in 
length, set in multiple rows on both upper and lower 
jaws. These features are plesiomorphic for the fam- 
