Sciaena intermedius (Koken, 1888)

Fig. 71 O–P

Otolithus (Sciaenidarum) intermedius Koken, 1888: 283, pl. 19, figs 2–3.

Otolithus (Sciaenidarum) intermedius – Campbell 1929a: 265, pl. 30, figs 2–3.

Corvina intermedia – Frizzell & Dante 1965: 694, pl. 88, figs 9–10, 27, 29–30.

“genus Sciaenidarum ” intermedia – Breard & Stringer 1999: 135.

?“genus aff. Umbrina ” livesayi – Müller 1999: 163, pl. 33, figs 23–30, pl. 34, figs 1–2.

“genus Sciaenidarum ” intermedius – Nolf 2003: 17, pl. 2, figs 12–14.

“ Sciaenida ” intermedia – Nolf 2013: 107, pl. 282.

Material examined

UNITED STATES OF AMERICA – Alabama • 76 otoliths; GLS otolith comparative collection (65 specimens), MSC 39042.1, MSC 39042.2, MSC 39042.4, MSC 39042.5, MSC 39042.6, MSC 39042.8, MSC 39042.14, MSC 39050, MSC 189, MSC 7302, WSU CC 473.1.

Description

Sagittae with approximately oval to subrectangular outline. Height/length ratios ranging from around 75–90%, typically around 80%. Inner face convex, smooth. Margins smooth except for juveniles, which may be finely sinuate. Dorsal margin slopes gently downward anteriorly and posteriorly from an obtuse central angle. Conspicuous posterodorsal angle. Posterior margin arches inward slightly; ventral margin broadly rounded. Anterior margin very broadly, evenly rounded. Very prominent heterosulcoid-type sulcus. Ostium filled with colliculum, covers about 35% of length of inner face. Anterior of ostium even with anterior margin of sagitta. Dorsal and ventral margins of ostium tend to constrict anteriorly; constriction often more pronounced on smaller (juvenile) specimens. Cauda long and narrow (less than 50% of width of ostium), has horizontal portion and sharply downturned portion. Horizontal portion of cauda about the same length as downturned portion, less excavated (but a variable feature). Downturned portion of cauda more excavated, about same width as horizontal portion. Angle of horizontal and downturned portions approximately 90-degrees. Downturned portion nearly reaches posteroventral margin. End of cauda tapered, still somewhat rounded. Outer face usually slightly concave, sculptured.

Remarks

There has been much debate about the taxonomic position of this species, and our decision to refer to it as Sciaena intermedius is defended in the ensuing discussion. The sagittae of S. intermedius are similar to those of Jefitchia copelandi and J. claybornensis (see below), and in fact S. intermedius is believed to be closely related to the two Jefitchia species. Frizzell & Dante (1965) proposed the fossil genus Jefitchia, and John Fitch, then Research Director of the California State Fisheries Laboratory, considered one of the most knowledgeable experts on sciaenid otoliths, confirmed that the genus was distinct from all known Recent sciaenids. In his treatise on modern and fossil Sciaenidae otoliths, Schwarzhans (1993) also considered Jefitchia as a valid fossil-based genus, and he accepted the two species proposed by Frizzell & Dante (1965). Sciaena intermedius could be considered as a possible species of Jefitchia, but it differs significantly from the original description of Frizzell & Dante (1965) and the subsequent description of Schwarzhans (1993) to be placed in this genus. One of the primary differences between the two is in the inflated ostium on S. intermedius. Frizzell & Dante (1965) noted the similarity of S. intermedius to J. copelandi, but they chose to assign the form to Corvina intermedia. Schwarzhans (1993) placed Sciaena intermedius into synonymy with the fossil-based Frizzellithus gemma, but Nolf rejected the fossil-based genus and insisted that F. gemma was actually Aplodinotus gemma (Nolf 2003, 2013). Furthermore, Nolf did not believe that S. intermedius belonged with Aplodinotus gemma and that it represented a separate species (Nolf 2003).

Sciaena intermedius bears a striking similarity to the late Eocene-Oligocene sciaenid Sciaena pseudoradians. Sciaena pseudoradians was originally described as Corvina pseudoradians by Frizzell & Dante (1965). Unfortunately, the holotype was not figured, and the figured paratypes were juvenile otoliths, which were not diagnostic. Nolf (2003) figured a growth series of the taxon and thought that the otoliths of this species seemed to be most closely related to those of Sciaena. Thus, the species S. pseudoradians was proposed. Sciaena intermedius has several major morphological features in common with S. pseudoradians, which can be clearly seen in figures 3–6 and 12–14 in plate 2 of Nolf (2013). The outline of the sagittae of the two species, the shape of the ostium, the angle of the downturned portion of the cauda, and the proportion of the horizontal and downturned portions of the cauda appear to indicate a close relationship. The width of the ostium of S. intermedius is variable, but it does not reach nearly the width of the ostium in S. pseudoradians. However, the width of the ostium of S. intermedius is much greater than Jefitchia copelandi or J. claybornensis. The relationship of S. intermedius to S. pseudoradians seems to be supported by geometric morphometric analyses reported by Lin (2018: fig. 5). According to his study, S. intermedius (reported as “ Sciaenda ” intermedia) may be closely related to S. pseudoradians. If S. intermedius is a transitional form to S. pseudoradians, this could explain the difficulty in determining its taxonomic position. It should also be noted that S. pseudoradians is primarily an Oligocene taxon, and that Nolf & Stringer (2003) identified the late Eocene form from the Yazoo Clay as Sciaena aff. pseudoradians. No specimens of Sciaena pseudoradians are known from the Claiborne Group.

The sagittae of Sciaena intermedius are somewhat similar to Jefitchia copelandi, which are also found in the Claiborne Group of Alabama. However, S. intermedius is distinguished by its appreciably wider ostium. The downturned portion of the cauda of J. copelandi also tends to be 90-degrees or greater measured from horizontal (Nolf 2013: pl. 281), whereas S. intermedius is typically less than 90-degrees from horizontal, which is shown well in the three specimens illustrated by Nolf (2013: pl. 282). The type locality for S. intermedius (as Corvina intermedia) was given as the Lisbon Formation at site AMo- 4 in Monroe County, Alabama (Frizzell & Dante 1965), and the species is also known from Louisiana, Mississippi, and Texas.

In his description of Eocene fishes of Alabama, White (1956) discussed a small collection of remains collected by G.F. Harris from the Gosport Sand of Claiborne, Monroe County, Alabama. Harris donated the material, which was composed primarily of shark teeth, to the British Museum in 1892, and a single otolith (P.6827) was included in the remains. White (1956) noted that the otolith belonged to Koken’s species Otolithus (Sciaenidarum) intermedius (Koken 1888: table 19, figs 2–3), which is the same as Corvina intermedia (Koken) of Frizzell & Dante (1965). However, White (1956) then stated that “Mr. Stinton” informed him that the specimen belonged to Lutianus. It is presumed that the “Mr. Stinton” refers to F.C. Stinton, a renowned expert on fossil otoliths, who published extensively on the Eocene otoliths of England. Although the otolith specimen was not examined as part of the present study, the background information provided by White (1956) is nevertheless problematic. If the otolith was correctly identified as Otolithus (Sciaenidarum) intermedius, then it is highly unlikely that Stinton would identify it as Lutianus (it should be noted that Lutianus is a rejected spelling for Lutjanus Bloch, 1790). Lutjanus is in Lutjanidae (the snappers), and lutjanid otoliths have little resemblance to Koken’s (1888) Otolithus (Sciaenidarum) intermedius. The sciaenid described by Koken has an inflated ostium and a narrow cauda that is downturned at almost 90-degrees, but Lutjanus displays none of these characteristics. Therefore, the identification of the Gosport Sand otolith recovered by Harris is unclear based on White’s (1956) discussion.

Stratigraphic and geographic range in Alabama

Sciaena intermedius is one of the most abundant taxa in the Claiborne Group of Alabama. It is common in the “upper” Lisbon Formation at site ACh-8 and six specimens were recovered from the Gosport Sand at sites ACl-4 and AMo-4. Bartonian, zones NP16 and NP17.