Carnevale et al.—Eocene priacanthid from Monte Bolca
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Figure 6. Pristigenys substriata (Blainville, 1818) from the Eocene of Monte Bolca, Italy: (1) NHM P.15371, reconstruction of the nuchal region showing the supraneural and the two anterior dorsal-fin pterygiophores, left lateral view; (2) NHM P.16370, reconstruction of the first haemal spine and anterior anal-fin pterygiophores, left lateral view; (3) NHM P.14540, reconstruction of the pelvic girdle, ventral view. All scale bars represent 2mm. See materials and methods section of text for anatomical abbreviations.
considered Pristigenys a close relative of Beryx, reinterpreting the identification by Volta (1796) and Blainville (1818) who considered it a member of the butterflyfish genus
Chaetodon.It is interesting to note, however, that Agassiz (1839) convin- cingly pointed out the similarities between Pristigenys and the Oligocene Acanus, the latter currently regarded as a subjective junior synonym of Priacanthus (Bannikov, 2010). Based on Agassiz’s comments, Woodward (1901) listed Pristigenys among the fossil representatives of the Berycidae, an opinion subsequently followed by Eastman (1905). Finally, White (1936) described new specimens in the collection of the British Museum (Natural History) (now The Natural History Museum, London) and, for the first time, referred this Eocene taxon to the family Priacanthidae, a placement supported by our morpho- logical analysis. Numerous features, other than overall physiognomy of the head and body, unquestionably demon- strate that Pristigenys substriata is a priacanthid (Fitch and Crooke, 1984; Starnes, 1988), including spinoid scales, scales covering the branchiostegals, infraorbital bones with serrated ventral margins, vertebrae 23 (10 + 13), principal caudal-fin rays 16 (8+8), fin spines deeply striated, single postcleithrum, and adnate pelvic fins. The relationships of Pristigenys substriata within the Priacanthidae were discussed by White (1936), who considered it almost indistinguishable from Pseudopriacanthus, pointing out that the differences between the Eocene and extant genera are inadequate to justify a separation above the species level. Myers (1958) reiterated the arguments discussed by White (1936) and indicated the correct generic name for Eocene and extant species would be Pristigenys. Since the publication by
White (1936), the skeletal morphology of Eocene priacanthids from Monte Bolca has been examined only superficially (Fritzsche and Johnson, 1981; Taverne, 1988), primarily to corroborate White’s conclusion that Pristigenys is the subjective senior synonym of Pseudopriacanthus. Although the synonymy of Pristigenys and Pseudopriacanthus has been accepted by many authors (e.g., Smith, 1966; Fritzsche and Johnson, 1981; Starnes, 1988; Taverne, 1988; Taverne and Nolf, 2010; Iwatsuki et al., 2012), several studies noted that there is no substantial evidence to support such a taxonomic assessment, suggesting that both genera should be retained as valid (e.g., Caldwell, 1962a, 1962b; Fritzsche, 1978; Fitch and Crooke, 1984). A close affinity between Pristigenys substriata and its (presumed) extant congenerics is supported by several shared features, including a deep, robust body (Figs. 1, 2), anterior and posterior ceratohyals joined by a narrow suture (Fig. 4.3), three upper plus three lower procurrent caudal-fin rays, a single supraneural (Fig. 6.1), an oblong supracleithrum, postpelvic process of the basipterygium expanded into a lobe (Fig. 6.3), a narrow ventral keel of the basipterygium (Fig. 6.3), and a black marginal band on the soft portions of the dorsal, anal, pelvic, and caudal fins (Fig. 2). However, the Eocene taxon exhibits a unique set of features that have not been observed in any of the extant or fossil species currently referred to Pristigenys (Starnes, 1988), suggesting generic separation. In particular, Pristigenys substriata is characterized by having a moderately developed orbit (Tables 1, 2), a short, deep caudal peduncle (Tables 1, 2), very elongate dorsal, anal, and pelvic fins (Table 1), spinules completely absent on median and paired fins
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