. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 340 Bulletin Museum of Comparative Zoology, Vol. 147, No. 7. HECQUI MULTIDENTATUS PARADOXUS ELAVIAE STRAELENI M1CR0LEPIS ECCENTRICUS Figure 14. Proposed phyletic relationships within the genus Perissodus. The greatest number of primitive char- acters has been found in P. hecqui and P. multidentatus. Both species retain (a) the generalized pattern of the three heads of the transversus dorsalis anterior muscle, (b) the well-developed obliquus posterior (Figs. 13B, D:TDA, OF), (c) a higher num- ber of jaw teeth than othe
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 340 Bulletin Museum of Comparative Zoology, Vol. 147, No. 7. HECQUI MULTIDENTATUS PARADOXUS ELAVIAE STRAELENI M1CR0LEPIS ECCENTRICUS Figure 14. Proposed phyletic relationships within the genus Perissodus. The greatest number of primitive char- acters has been found in P. hecqui and P. multidentatus. Both species retain (a) the generalized pattern of the three heads of the transversus dorsalis anterior muscle, (b) the well-developed obliquus posterior (Figs. 13B, D:TDA, OF), (c) a higher num- ber of jaw teeth than other related species, (d) the elongate mandible, and (e) the rounded shape of the articular apophyses on the dorsal surfaces of the third pharvngo- branchials (Fig. 13B, D). P. hecqui appears to be the most primitive representa- tive of this lineage since it is the only species with a relatively unspecialized pala- tine, an unmodified adductor arcus palatini, and a preopercular with a shallow and relatively restricted adductor fossa. Al- though P. hecqui and P. multidentatus differ from each other in respect to denti- tion, number of gill rakers in the lower part of the first arch, and the distal con- figuration of the mandible, the two taxa can be regarded as sister species since they share the character of an increased number of gill rakers in the lower part of the first gill arch (Fig. 14). In all other, more .specialized species, the second head of the transversus dorsalis anterior is lost, the obliquus posterior be- comes atrophied, and the mandible is shortened and deepened (Figs. 13, 5, 6). The articular apophyses on the dorsal sur- face of the third pharyngobranchial be- comes elongate (Fig. 13A, C), the anterior levator interims is hypertrophied (Fig. 13:LI), and the greatly enlarged jaw teeth are either curled inwardly or become truncated or obtusely pointed (Plates 1 2- Figs. 23-31). We can recognize a clear dichotomy in the five specialized species. In one lineage comp
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