558
Journal of Paleontology 91(3):554–565
The outer margin of the skull roof is nearly straight, whereas that of the ethmoid region appears to be convex. The frontals are the largest bones of the skull roof. A low sagittal crest appears to be present. The supraorbital margin of the frontal is smooth. The mesethmoid is rather thick. The lateral ethmoids are character- ized by a large laminar lateral flange with a rounded outer margin. The supraoccipital crest is relatively large, reaching its maximum height just above the midlength of the orbit. The parasphenoid is robust and nearly straight for most of its length, forming a shallow angle at the level of the posterior orbital wall. The basisphenoid is columnar and nearly perpendicular to the parasphenoid.
Figure 3. Pristigenys substriata (Blainville, 1818) from the Eocene of Monte Bolca, Italy: MNHN
F.Bol529, abdominal scales. Scale bar represents 1mm.
between 1.4 and 1.6 times in that of the third spine. The longest (third) anal-fin soft ray is remarkably longer that the longest anal-fin spine. The soft portion of the anal fin has a gently rounded outer profile. The caudal fin is rounded, and its length is contained about four times in SL. The pectoral fins are incom- plete in all examined specimens; however, they appear to be rather short. The pelvic fin insertion is located beneath the pectoral-fin base. The prepelvic distance is contained between 1.75 and 2.5 times in SL. The pelvic fin is adnate and remark- ably elongate (pelvic-fin length less than half SL), extending posteriorly well beyond the anal-fin insertion (Fig. 2.5, 2.6). The rays of the dorsal, anal, caudal, and pelvic fins are characterized by a remarkably well-preserved black marginal band (Figs. 1,2).
Squamation.—The body is covered by thick, adherent spinoid scales (type 1 of Roberts, 1993) (Fig. 3). The scales are poly- gonal in outline with a nearly straight anterior margin and a weakly pointed or convex posterior margin. The spines are stout, variable in size, their number ranging from 15 to ~25. The scales appear to be smaller, irregularly arranged, and structu- rally modified on the nape, top of the head, gular (including the branchiostegals) and prepectoral areas, opercle, chin, and cheek; although their precise morphology is unclear, at least those of the cheek and some of those of the chin seem to bear spines emerging from their outer surfaces. The circuli of the body scales are characterized by a rough texture, ostensibly related to the presence of microscopic denticles (Starnes, 1988). The lat- eral line runs very high on the body flank, following the dorsal profile of the body up to the posterior end of the caudal peduncle. The lateral-line scales bear a single tube.
Neurocranium.—Overall, the skeletal morphology is consistent with that of other priacanthid fishes (see Starnes, 1988; Taverne and Nolf, 2010). The skeletal structure of the skull is only par- tially recognizable due to the extensive fragmentation of most of the bones. The neurocranium is robust, compact, and relatively deep, about 1.5 times as long as deep (Fig. 4.1). Due to the presence of a large orbit, both the ethmoid and postorbital por- tions of the neurocranium are anteroposteriorly compressed.
Infraorbital series.—The bones of the infraorbital series are in general moderately well preserved (Fig. 4.2). A partially pre- served and articulated series is exposed in the holotype. The lacrimal has a serrated ventral margin with a large stout spine emerging from its midlength. The third infraorbital is char- acterized by a relatively large subocular shelf (see Smith and Bailey, 1962). The fourth, fifth, and sixth infraorbitals are preserved in specimen NHM P.15371; their ventral margin is serrated (Fig. 4.2). The nasal and supratemporal bones are not recognizable in the examined material.
Jaws.—The premaxilla has robust ascending and articular pro- cesses.Apostmaxillary process is not preserved, although it was possibly present originally. The alveolar process is elongate and rather thick, bearing numerous irregularly arranged small con- ical teeth with slightly recurved tips. The maxilla has an expanded and spatulate distal end. The lower jaw is upturned and projects strongly. The craniomandibular articulation is located just below the anterior margin of the orbit. The dentary is stout and very thick at the symphysis, where it bears a short ventral process. There are numerous teeth along the dorsal margin of this bone, very similar to those of the premaxilla. The anguloarticular and retroarticular are very robust.
Suspensorium.—The morphology of the bones of the suspen- sorium is consistent with that of other priacanthid fishes (Starnes, 1988). The endopterygoid and ectopterygoid are well preserved in specimens NHM P.16370 and NHMP.14540. The endopterygoid is large and ovoid in outline. The palatine bears a strong finger-like maxillary process, which is well exposed in specimen NHM P.16127. The quadrate is fan-shaped. The symplectic is relatively short. The hyomandibular is always fragmented and inadequately preserved.
Opercular series.—The bones of the opercular series are poorly preserved due to their extensive fragmentation. The crescent- shaped preopercle has finely serrated posterior and ventral margins, and a moderately developed, finely serrated spine at the posteroventral angle (Fig. 4.3). The bony shelf overlying the preopercular sensory canal is smooth. The interopercle is partially preserved in the specimen NHM P.16127; it is oblong with a pointed anterior end and a finely serrated ventral margin.
Hyoid apparatus and gill arches.—The hyoid bar is robust and strongly ossified (Fig. 4.3). The dorsal and ventral hypohyals are
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