. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 80 Bulletin Museum of Comparative Zoology, Vol. 150, No. 2 0) o o <u <u (U o "O o T3 o ;o *C E X o o E t/) o o O O CO Salmonoidea. Salmonoidei Salmonae Figure 22. Rosen's (1974) hypothesis of choice for protacanthopterygian relationships. of the group that "keys out" at that cou- plet. In some cases, characters were used as synapomorphies at several levels in the key, without explanation. In spite of the confusing structure of the key, a care- ful reading of it, combined with a reading of the text
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 80 Bulletin Museum of Comparative Zoology, Vol. 150, No. 2 0) o o <u <u (U o "O o T3 o ;o *C E X o o E t/) o o O O CO Salmonoidea. Salmonoidei Salmonae Figure 22. Rosen's (1974) hypothesis of choice for protacanthopterygian relationships. of the group that "keys out" at that cou- plet. In some cases, characters were used as synapomorphies at several levels in the key, without explanation. In spite of the confusing structure of the key, a care- ful reading of it, combined with a reading of the text, does provide some characters which appear to be diagnostic of the var- ious groups recognized by Rosen. Our discussion of Rosen's hypotheses follows the sequence of taxa as given in his key, which the reader may wish to consult. The Protacanthopterygii was never ex- plicitly diagnosed by Rosen, but the char- acters which he suggested to unite eso- coids (including Lepido^alaxias) with the other lineages can be construed as protacanthopterygian synapomorphies. These characters were discussed on page 310 and include fusion of a toothplate (when present) to the third pharvngo- branchial and presence ol "a posterior toothplate below the fourth pharyngo- branchial and fourth epibranchial in a pattern like that of the 'well toothed' sal- ; However, the first of these characters is probably clupeocephalan, since fusion of the toothplate occurs not only in salmoniforms but also in Etru- meus, ostariophysans, stomiiforms, and almost all eurypterygians (with the ex- ception of the Ateleopodidae, noted by Rosen, 1973: 487). Concerning the sec- ond character, Rosen did not precisely define the pharyngobranchial toothplate "pattern" or "well toothed, " but we as- sume that he is referring to the presence of but a single toothplate associated with the fourth pharyngobranchial and fourth epibranchial. This character has a distri- bution in the Protaca
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