Elopothrissus undetermined

Stringer, Gary L. & Sloan, James Carson, 2023, First Cretaceous teleostean otolith assemblage (Arkadelphia Formation, upper Maastrichtian) from Arkansas, USA, early Gadiformes, and the Western Interior Seaway, PaleoBios 40 (1994), pp. 1-39 : 8-9

ELOPOTHRISSUS SP.

FIG. 5C

Material— one specimen, DMNH 2021-09- 03 .

Description and Remarks— The one elongate specimen assigned to Elopothrissus has a prominent sulcus clearly divided into an oval ostium opening anteriorly and

anterodorsally, and a narrower, longer more excavated cauda. However, as noted in Schwarzhans and Stringer (2020a) there are significant changes in the H/L ratios with ontogenetic changes in size, which is caused primarily by an increase in the length of the rostrum. There is a slight postdorsal angle as well as some faint marginal crenulation. Like with many other pterothrissids, morphological maturity is only reached when specimens are more than 5 mm long, hence, smaller specimens should not be used for species definition ( Schwarzhans 2012). For this reason, DMNH 2021-09-03, which is only 1.83 mm long, is identified only to genus.

Elopothrissus carsonsloani Schwarzhans and Stringer (2020a) was reported from the Danian Clayton Formation but not the Maastrichtian Kemp Clay ( Schwarzhans and Stringer 2020a). An unidentified species of Elopothrissus was noted by Schwarzhans et al. (2018b) from the Santonian of Alabama. The genus represents an extinct pterothrissid that extends across the K-Pg extinction event and well into the Paleogene ( Schwarzhans and Stringer 2020a).

Figures

Figure 5. Otoliths from the Cretaceous Arkadelphia Formation. All specimens unless otherwise noted are inner views of right sagittae. Length in mm. A. Elops sp., DMNH 2021-09-01, 1.89 mm. B. Albuliformes indeterminate, DMNH 2021-09-02, 1.42 mm. C. Elopothrissus sp. DMNH 2021-09-03, 1.83 mm. D. Genartina sp. DMNH 2021-09-04, 0.85 mm. E. Osmeroides sp. DMNH 2021-09-05, 3.85 mm. F. Anguilla? chickasawae Schwarzhans and Stringer (2020b), DMNH 2021-09-6, 1.90 mm. G. Echiophis aff. E. semisphaeroides Schwarzhans (2003), DMNH 2021-09-07, 3.25 mm. H. Muraenanguilla? sp. DMNH 2021-09-08, 2.18 mm.