Pycnodus, Agassiz, 1835

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 : 152-154

Pycnodus sp.

Fig. 57 A–L

Albula sp. – Clayton et al. 2013: fig. 6i–j. — Maisch et al. 2016: fig. 2, 1–2.

Material examined

UNITED STATES OF AMERICA – Alabama • 20 isolated teeth; Claiborne Group; MSC 35773.1–8, MSC 37185, MSC 37912.1–2, MSC 38483.1–6, NJSM 24037, SC 2012.47.128, WSU 36, WSU CC 560.

Description

Taxon known in Alabama only from isolated teeth. Teeth measure up to 6.0 mm in greatest diameter. Teeth have an oval outline in occlusal view and have a convex occlusal surface. Teeth may also have a flat medial crown surface. Teeth have a thick enamel covering that is smooth and extends to the base of the crown. There is a large oval basal pulp cavity. The occlusal surface of worn teeth is punctate.

Remarks

Several species of Pycnodus have been reported from Paleogene strata, including P. variabilis Stromer, 1905b (also Stromer 1910); P. toliapicus Agassiz, 1843 ; and P. pellei Priem, 1902 . In Alabama the taxon is known only from isolated teeth, and intraspecific variation within the dentitions of this genus is poorly known. This factor, coupled with our small sample size (n =20), precludes a more precise taxonomic assignment. Clayton et al. (2013: fig. 6i–j) illustrated a Pycnodus sp. tooth that was incorrectly identified as Albula sp. Based on our Claiborne Group sample, teeth of Pycnodus sp. can be differentiated from Albula in having a more convex occlusal surface, thicker enameloid covering, and large basal pulp cavity. Additionally, worn Pycnodus teeth are punctate. Inexplicably, Maisch et al. (2016) stated that their specimens of Albula sp. were similar to material from Alabama reported by Clayton et al. (2013: fig. 6ij), but the specimen specifically referred to, incorrectly identified as Albula , is actually Pycnodus sp. Additionally, the tooth shown by Clayton et al. (2013) is practically identical to the Pycnodus sp. tooth Maisch et al. (2016: fig. 2, 1–2) figured in their study.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the lower Tallahatta Formation at site ADl-1, the contact of the Tallahatta and Lisbon formations at sites ACh-14 and ACov-11, and the basal Lisbon Formation at site ACov-11. Upper Ypresian to lower Lutetian, zones NP14 and NP15.

Figures

Fig. 57. Pycnodus sp., teeth and Lepisosteidae elements. A–L. Pycnodus sp. A–C. MSC 35773.1, tooth, lower Tallahatta Formation. A. Oral view. B. Profile view. C. Aboral view. D–F. MSC 35773.2, tooth, lower Tallahatta Formation. D. Oral view. E. Profile view. F. Aboral view. G–I. MSC 37185, tooth, Tallahatta/Lisbon formation contact zone, courtesy of T. Prescott Atkinson. G. Oral view. H. Profile view. I. Aboral view. J–L. MSC 37912.1, tooth, basal Lisbon Formation. J. Oral view. K. Profile view. L. Aboral view. — M–BB. Lepisosteidae Cuvier, 1825. M–N. ALMNH PV1989.4.70, scale, Gosport Sand. M. External view. N. Internal view. O–P. ALMNH PV1989.4.37.2.1, scale, Gosport Sand. O. External view. P. Internal view. Q–R. ALMNH PV1989.4.37.2.2, scale, Gosport Sand. Q. External view. R. Internal view. S–T. MSC 37306, scale, basal Lisbon Formation. S. External view. T. Internal view. U–V. MSC 37473.1, tooth, basal Gosport Sand. U. Lateral view. V. Basal view. W–Y. ALMNH PV1989.2.4, vertebra, Gosport Sand. W. Anterior view. X. Left lateral view. Y. Posterior view. Z– BB. ALMNH 1898.4.190, vertebra, Gosport Sand. Z. Anterior view. AA. Left lateral view. BB. Posterior view. Scale bars for A–L=2 mm. Scale bars: M–T, W–BB =1 cm; U =5 mm.