Albula eppsi White, 1931

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L., 2019, Taxonomy and biostratigraphy of the elasmobranchs and bony fishes (Chondrichthyes and Osteichthyes) of the lower-to-middle Eocene (Ypresian to Bartonian) Claiborne Group in Alabama, USA, including an analysis of otoliths, European Journal of Taxonomy 585, pp. 1-274 : 161-163

Albula eppsi White, 1931

Fig. 60 A–I

Albula eppsi Frost in White, 1931: 83 , figs 137–141.

Albula sp. – Maisch et al. 2016 (partim): fig. 2.5–6 (non 7–8).

Material examined

UNITED STATES OF AMERICA – Alabama • 33 isolated teeth; Claiborne Group; MSC 37358.1–2, MSC 37541, MSC 37909.1–6, MSC 38445.2–24, NJSM 24039.

Description

Low-crowned teeth, circular occlusal outline; occlusal surface of unworn teeth nearly flat to convex. Crown enameloid thin, smooth, generally not reaching tooth base. Worn teeth flat, with occlusal surface often oblique to tooth height, triturating surface composed of dentine. Lateral tooth edges range from convex to parallel tapering. Tooth base flat; circular basal pulp cavity centrally located.

Remarks

Teeth exhibiting the morphology described above have traditionally been assigned to either Albula oweni Owen, 1845 or Albula eppsi Frost in White, 1931 . White (1931) differentiated these species based on tooth size, with small teeth measuring less than 2.0 mm in diameter being assigned to A. eppsi and larger teeth to A. oweni . Casier (1966), however, synonymized the two species and suggested that A. eppsi represented the juvenile morphology of A. oweni . Forey (1973), however, proposed that A. eppsi and A. oweni were distinct taxa, noting that teeth of an intermediate size between the two were unknown. Weems (1999) came to the same conclusion based on a sample from the lower Eocene Nanjemoy Formation in Virginia, which included two Albula tooth plates bearing small teeth, indicating to him a small adult Albula morphology coexisted with the larger Albula oweni .

Our Albula sample includes teeth ranging in diameter from 1.0 mm to nearly 9.0 mm. This size gradient contradicts the observations of Forey (1973), possibly indicating that the varying sizes are related to heterodonty and/or ontogeny within a single species. However, unlike the parasphenoids of extant Albula vulpes (Linneaus, 1758) , where large medial teeth are flanked by smaller teeth that gradually decrease in size towards the plate margins (see Clothier 1950: fig. 22), teeth on A. oweni parasphenoids only slightly decrease in size across the tooth plate (see Owen 1845: pl. 47, fig. 3; Woodward 1893: pl. 17). This suggests that within fossil members of Albula , monognathic heterodonty is not the determining factor with regard to tooth size, but is instead related to ontogeny and/or interspecific variation.

Irrespective of size, our Albula tooth sample includes two morphologies, including those with lateral sides that taper basally towards the pulp cavity, and those with lateral edges that are straight or weakly convex. Of the teeth that exceeded 5.0 mm in diameter, all have tapered lateral edges and are consistent in size with the type specimens for A. oweni as illustrated by Owen (1845: pl. 47, fig. 3) and Casier (1966: pl. 13, fig. 4). Thus, we assigned all teeth with tapered edges to this taxon. Of the teeth with a diameter of less than 5.0 mm, all have straight and parallel lateral edges, or the edges were biconvex. These teeth appear conspecific to those described as Albula eppsi by Weems (1999). This difference in tooth morphology suggests that two species of Albula are indeed present within Claiborne strata in Alabama.

Although the teeth in our sample suggest that both A. eppsi and A. oweni are present, complications exist concerning the use of the name Albula eppsi . White (1931) originally named this taxon based on numerous dental elements with teeth, an operculum, and 40 otoliths that were derived from the lower Ypresian London Clay in the UK. The dental elements and teeth were given the name Albula eppsi while the otoliths, following the convention of the time regarding otolith-based species, was assigned to Otolithus (Albula) eppsi Frost in White (1931) . Several years earlier, Priem (1908) erected the species Otolithus (Trachini?) bellevoyei based on isolated otoliths collected from Thanetian deposits in France. Nolf (2013) recently determined that the Albula eppsi otoliths were conspecific with the otolith-based Albula bellovoyei , rendering the otoliths of the former a junior synonym of the latter. This creates a taxonomic dilemma for several reasons. First, both White (1931) and Casier (1966) reported two species of Albula within the London Clay, A. oweni and A. eppsi , and their differing dental morphologies support that these are indeed two unique and valid species. The otoliths from the London Clay should therefore belong to one of these two species, rather than represent a third coeval species, A. bellovoyei . Thus, if it could be conclusively determined that the otoliths are indeed associated with the A. eppsi bony material, all should be referred to A. bellovoyei . One the other hand, if it were determined that the otoliths belong to A. oweni , A. bellovoyei would be designated a junior synonym of A. oweni because this latter species was named decades earlier, in 1845. Bearing these taxonomic issues in mind, we choose to assign the small Claiborne Group teeth described above to A. eppsi as there is currently no definitive link between the teeth described by White (1931) and A. bellovoyei otoliths.

Our reexamination of a tooth figured by Maisch et al. (2016: fig 2, 5–6) as Albula sp. (NJSM 24039) from the Tallahatta/ Lisbon contact at site ACh-14 shows it has convex lateral edges, and we identify it as Albula eppsi . Furthermore, several specimens identified by Case (1994b: 142, pl. 1, figs 372–375) as A. eppsi from the lower Eocene Tuscahoma Sand in Lauderdale County, Mississippi instead belong to Fisherichthys folmeri (see Weems 1999; Cicimurri & Knight 2009).

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the lower Tallahatta Formation at site ADl–1, the Tallahatta Formation at site AMo–8, the contact of the Tallahatta and Lisbon formations at site ACh-14, the basal Lisbon Formation at site ACov–11, and the basal Gosport Sand at site ACl–4. Upper Ypresian to middle Bartonian, zones NP14 to NP17.

Figures

Fig. 60. Albula eppsi White, 1931 and Albula oweni (Owen, 1845), teeth. A–I. Albula eppsi A–C. MSC 38445.1, lower Tallahatta Formation. A. Oral view. B. Profile view. C. Aboral view. D–F. MSC 37909.1, basal Lisbon Formation. D. Oral view. E. Profile view. F. Aboral view. G–I. MSC 37541, basal Gosport Sand. G. Oral view. H. Profile view. I. Aboral view. — J–R. Albula oweni. J–L. MSC 38445.1, lower Tallahatta Formation. J. Oral view. K. Profile view. L. Aboral view. M–O. MSC 37891, “upper” Lisbon Formation. M. Oral view. N. Profile view. O. Aboral view. P–R. MSC 37699, basal Gosport Sand. P. Oral view. Q. Profile view. R. Aboral view. Scale bars = 2 mm.