Carnevale et al.—Eocene priacanthid from Monte Bolca
species formerly referred to Pseudopriacanthus to the fossil genus Pristigenys based on a few morphological and meristic features, confirming the hypothesis proposed by White (1936) and subsequently reiterated by Myers (1958), Fritzsche and Johnson (1981), and Taverne (1988). However, the skeletal morphology of the type species of the genus Pristigenys—the Eocene P. substriata from Monte Bolca—has never been examined in detail in order to conclusively demon- strate its affinity to the extant species formerly referred to Pseudopriacanthus. The goal of this paper is therefore to describe the osteology of Pristigenys substriata in more detail, and to discuss its relationships with the extant members of the Priacanthidae.
Stratigraphy
The celebrated locality of Monte Bolca lies in the eastern part of Monti Lessini, near Verona, northeastern Italy. This locality includes several productive sites, two of which, the Pesciara and Monte Postale, have provided one of the most important and well-known fossil fish assemblages of the world (see Carnevale et al., 2014). The best known of these sites is that of the Pesciara, which is characterized by abundant and exquisitely preserved fossils, particularly fishes (Marramà et al., 2016). The fish- bearing deposits of the Pesciara site pertain to the so-called ‘Calcari Nummulitici’, an informal Eocene unit widespread in the surroundings of Monte Bolca, and consist of finely lami- nated micritic limestone. According to Marramà et al. (2016), the fossiliferous deposits of the Pesciara site accumulated in a shallow intraplatform basin in which anoxic conditions at the bottom and the development of a biofilm promoted the high- quality preservation of its fossils. The age of the fish-bearing laminated limestone of the
Pesciara site has been defined on the basis of their large benthic Foraminifera. These deposits have been referred to the Alveolina dainelli Zone, or to the SBZ 11 Biozone, corre- sponding to the late Cuisian (late Ypresian, slightly less than 50 Ma; Papazzoni et al., 2014).
Materials and methods
The fossil material documented herein consists of five well- preserved complete to nearly complete articulated skeletons preserved on the surface of laminated micritic limestone. The preservation quality of the examined specimens, as well as the lithology of the associated sediment, suggest that skeletal material belonging to Pristigenys substriata documented herein derive from the excavations carried out at the Pesciara site (see Marramà et al., 2016). The material was examined using Wild M5A and Leica M80 stereomicroscopes equipped with camera lucida. Measurements were taken using a dial caliper, to the nearest 0.1mm. During examination, the specimens were moistened with alcohol to enhance some details of their skeletal anatomy.
Repositories and institutional abbreviations.—The fossils are housed in the collections of the Natural History Museum, London (NHM) and the Museum National d’Histoire Naturelle, Paris (MNHN).
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Anatomical abbreviations.—ach, anterior ceratohyal; ap1, first anal-fin pterygiophore; br, branchiostegals; bsp, basisphenoid; dhh, dorsal hypohyal; dp1, first dorsal-fin pterygiophore; ep, epural; f, frontal; hpu2, haemal spine of the second preural
vertebra; hpu3, haemal spine of the third preural vertebra; hs1, first haemal spine; hyp, hypural; io3, third infraorbital bone; lac, lacrimal; le, lateral ethmoid; me, mesethmoid; npu2, neural spine of the second preural vertebra; pas, parasphenoid; pch, posterior ceratohyal; phy, parhypural; pop, preopercle; pp, postpelvic process; SL, standard length; sn, supraneural; soc, supraoccipital; ss, subocular shelf; uh, urohyal; un, uroneural; v, vomer; vhh, ventral hypohyal; vk, ventral keel of the basipterygium.
Systematic paleontology
Percomorphacea sensu Wiley and Johnson, 2010 Family Priacanthidae Gill, 1872 Genus Pristigenys Agassiz, 1835
Type species.—Chaetodon substriatus Blainville, 1818. Included species.—Type species, by monotypy.
Diagnosis.—A deep-bodied priacanthid unique in having the following combination of character-states: orbit moderately large (orbit diameter 14.1–19.6% SL); caudal peduncle short (9.1–11.9% SL) and deep (17.3–20.1% SL); sagittal crest (apparently) present; frontal with smooth supraorbital margin; shelf overlying the preopercular sensory canal smooth; pre- opercular spine stout; anterior and posterior ceratohyal joined by narrow suture; first haemal spine greatly enlarged and closely associated with anterior anal-fin pterygiophores; single supra- neural; dorsal fin containing ten strong and deeply striated spines plus nine to 12 soft rays; dorsal-fin spines and soft rays well developed (longest spine 26.1–32.7% SL; longest ray 27.1–35.6% SL); anal fin containing three strong and deeply striated spines plus nine to 12 rays; anal-fin rays considerably elongate (longest ray 19.7–37.9% SL); pelvic fins remarkably elongate (49.7–57.7% SL); postpelvic processes of basipterygia expanded into lobes; ventral keel of basipterygia narrow; black marginal pigmented band on soft portion of dorsal, anal, caudal, and pelvic fins; caudal fin rounded, with three upper and three lower procurrent rays; spinules absent in all fins; body scales with about 15–25 stout spinules on posterior margin.
Occurrence.—As for Pristigenys substriata, the type and only known species.
Pristigenys substriata (Blainville, 1818) Figures 1–6
1796 Chaetodon striatus Volta, p. 92, pl. 20, fig. 2. 1818 Chaetodon substriatus Blainville, p. 352. 1835 Pristigenys macrophthalmus Agassiz, p. 313.
1839 Pristigenys macrophthalmus Agassiz, p. 136, pl. 18, fig. 2.
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