. Bulletin of the British Museum (Natural History) Zoology. mp*. Fig. 15 PBO of A, Oedalechilus labeo (BMNH : 1-10, mm SL); B, Oedalechilus labiosus (: 1709-15, 83 mm SL); C, Crenimugil crenilabis (: 623-30, 107 mm SL); D, Rhinomugil corsula (: 89-98, mm SL). Lateral views of right side. cheilus, the sulcus is more extensive than in any other Liza and possibly mugilid species (Fig. 18B). Liza abu more closely resembles Mugil in having both a large, lateral denticulate area and a large, single valve (Fig. 18E). A third group of species with the
. Bulletin of the British Museum (Natural History) Zoology. mp*. Fig. 15 PBO of A, Oedalechilus labeo (BMNH : 1-10, mm SL); B, Oedalechilus labiosus (: 1709-15, 83 mm SL); C, Crenimugil crenilabis (: 623-30, 107 mm SL); D, Rhinomugil corsula (: 89-98, mm SL). Lateral views of right side. cheilus, the sulcus is more extensive than in any other Liza and possibly mugilid species (Fig. 18B). Liza abu more closely resembles Mugil in having both a large, lateral denticulate area and a large, single valve (Fig. 18E). A third group of species with the denticulate area reduced, the teeth fine and evenly graded and the sulcus diagonal and wide, includes: L. grandisquamis (Fig. 18D), L. parmatus, L. seheli and L. waigiensis (Fig. 18C). DISCUSSION Agonostomus is the most plesiomorphic mugilid in terms of its PBO structure since it lacks the more developed organ of other taxa. The pharyngobranchial teeth are directly attached to the 2nd and 3rd pharyngobranchials and 4th toothplate; the levator internus 2 is narrow and the retractor dorsalis is a single (paired) muscle. These characters all seem to represent the least specialised condition seen in the Mugilidae. Schultz (1946) distinguished Agonostomus from other mugilids on the basis of what are plesiomorphic features ie., broad band of teeth attached to jaw, lack of marginal teeth, absence of lip folds, broadly rounded lower jaw, long maxilla and absence of adipose eyefold tissue. In constructing a phylogeny for the Mugilidae (Fig. 20) our polarity assignments for PBO morphotypes are based on the premises that Agonostomus represents the plesiomorphic lineage (on characters other than the absence of a PBO; see above) and that during ontogeny the more general precedes the less general condition (L0vtrup, 1978; Nelson, 1978; Fink, 1982). The latter sequence is evident in the possession of proximal-type pharyngobrancial teeth in the earliest stages of all mugilids which are later r
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