. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 146 Bulletin Museum of Conipanitwe Zoology, Vol. 150, No. 3 RAB UP3 F PB1. UP2 F Figure 34. Dorsal gill arch elements and the retractor dorsalis (RAB) muscle in the aulopiform Aulopus (ventral view). The muscle fans out to insert on the third and fourth pharyngobranchials and fourth epibranchial. The second epibran- chial (Ej) has a prominent uncinate process (E,UNC. PROC). (Modified from Rosen, 1973.) Other Abbreviations: E, 4, epibranchials; PB, 4, pharyngobranchials; RAB, retractor arcuum branchialium or
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 146 Bulletin Museum of Conipanitwe Zoology, Vol. 150, No. 3 RAB UP3 F PB1. UP2 F Figure 34. Dorsal gill arch elements and the retractor dorsalis (RAB) muscle in the aulopiform Aulopus (ventral view). The muscle fans out to insert on the third and fourth pharyngobranchials and fourth epibranchial. The second epibran- chial (Ej) has a prominent uncinate process (E,UNC. PROC). (Modified from Rosen, 1973.) Other Abbreviations: E, 4, epibranchials; PB, 4, pharyngobranchials; RAB, retractor arcuum branchialium or retractor dorsalis muscle; TP, toothplate; TP-F, toothplate fused with endoskeleton; UP, upper pharyngeal toothplate. and the division of die retractor dorsalis mnscle into distinct medial and lateral components or heads (Rosen, 1973). The smaller medial head inserts on the third pharynj2;obranchial, whereas the lateral component retains the original or primi- tive insertion on the fbnrth pharyngo- branchial and its tooth-plate (Fig. 35). The appearance of the medial head of the re- tractor dorsalis inserting on the third piiar\ ngohranchial indicates that the myctophifbrms are aligned with the paracanthopterygians and acanthoptery- gians rather than with the Aulopiformes (Rosen, 1973). The dnal insertions of the retractor dorsalis on the third and fourth pharv iigohranchials in myctophiforms furnish the basic system from which the more specialized upper pharyngeal jaws of the paracanthopterygians and acan- thopterygians were derived. In myctoph- ifbrms we can see the beginning of the trend towards an increasing emphasis on the third phar\ ngobranchial as the dom- inant tooth-bearing element in the upper pharyngeal jaw in advanced euteleos- teans. Concomitanth in some Acantho- morpha there is a shift of the insertion of the retractor dorsalis from the fourth, or third and fourth, to an exclusive insertion on the third pharxiigobranchial. The Myctophidae (lantern f
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