Aetobatus sp, de Blainville, 1816

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, inclu, European Journal of Taxonomy 585, pp. 1-274: 123-125

publication ID

https://doi.org/10.5852/ejt.2019.585

publication LSID

lsid:zoobank.org:pub:181B6FBA-ED75-4BB4-84C4-FB512B794749

DOI

http://doi.org/10.5281/zenodo.3664667

persistent identifier

http://treatment.plazi.org/id/18174D41-FFFF-FFD3-FD0F-9D294CF10D80

treatment provided by

Plazi

scientific name

Aetobatus sp
status

 

Aetobatus sp  .

Fig. 44View Fig

Aetiobatis sp. cf. A. irregularis – Thurmond & Jones 1981: 75  , fig. 36b.

Aetobatis sp.  – Holman & Case 1988: 328.

Aetobatus irregularis – Cappetta & Case 2016: 66  , pl. 14, fig. 1.

Material examined

UNITED STATES OF AMERICA – Alabama • 127 isolated teeth; Claiborne Group ; GSA-V699, MMNS VP-5642 (2 specimens), MMNS VP-5648, MSC 2389.1 11, MSC 37150View Materials (4 specimens), MSC 37184View Materials (3 specimens), MSC 37244View Materials (2 specimens), MSC 37255View Materials (9 specimens), MSC 37303View Materials (15 specimens), MSC 37330View Materials (7 specimens), MSC 38806View Materials (2 specimens), MSC 38810View Materials (14 specimens), MSC 38830View Materials (3 specimens), MSC 38947View Materials, NJSM 24031View Materials, NJSM 24032View Materials, SC 2012.47.23, SC 2012.47.24, SC 2012.47.25, SC 2012.47.26, SC 2012.47.27, SC 2012.47.28 (4 specimens), SC 2012.47.29 (2 specimens), SC 2012.47.211 (29 specimens), SC 2012.47.212, SC 2012.47.213, SC 2012.47.214, SC 2012.47.215, SC 2012.47.216, SC 2012.47.217, SC 2012.47.218, SC 2012.47.219, WSU 5012View Materials, WSU 5023View Materials  .

Description

Upper and lower tooth plates consist of a single median file. In oral view, tooth crowns very wide but narrow. Teeth in upper dentition straight, sinuous, or weakly arcuate (convex labially) in outline. Teeth in lower dentition strongly arcuate or chevron shaped. Distal ends of crown within both dentitions are straight and perpendicular to width, basally curving and slightly lingually directed. The labial crown face overhangs the root; root extends well beyond the lingual side of the crown. Both crown faces ornamented with fine vertical wrinkles; thick and rounded transverse ridge present at lingual crown foot. Root polyaulacorhize; numerous thin lamellae present on basal and dorsal surfaces. Labial root face oblique (basiolingually directed); may bear shallow grooves that are in line with lamellae.

Remarks

Partial teeth of Aetobatus  could be confused with Pseudaetobatus  (see below), although there is currently no evidence that the two taxa were coeval within the Claibornian of Alabama. There are no lateral teeth in the Aetobatus  dentition, and the distal ends of individual teeth are straight and perpendicular to the width, basally curving, and lingually directed. In contrast, distal ends of Pseudaetobatus  median teeth are angular and form a point of articulation for lateral teeth.

Aetobatus  does occur with several other Myliobatinae  within Claibornian strata. Tooth crowns of Aetobatus  lack the thickened, tuberculated enameloid seen on the occlusal surface of Leidybatis  teeth, and the ornament on the vertical crown faces is only weakly developed. A reticulated pattern of beaded ridges and pitting on the vertical crown faces, angular lateral margins, and the sharp and narrow lingual transverse ridge distinguish Aetomylaeus  from Aetobatus  . Myliobatis  teeth are more similar to Aetomylaeus  than Aetobatus  . Although the teeth of both Aetobatus  and Rhinoptera  ( Rhinopterinae  ) have a crown with similar ornament and cross section, the labial root face of Aetobatus  is oblique and the lingual root margin extends well past the crown, whereas the labial root face on Rhinoptera  teeth is low and vertical, and the lingual margin generally does not extend past the lingual crown foot.

Eocene specimens of Aetobatus  are often assigned to A. irregularis  . However, we could not directly compare the Lisbon material to the type specimens and therefore cannot confidently assign our incomplete specimens to A. irregularis  . Additionally, Hovestadt & Hovestadt-Euler (2013) demonstrated that dentitions of extant myliobatin taxa exhibit varying degrees of intraspecific variation, and it is difficult to ascertain if the generally fragmentary, globally distributed remains typically identified as A. irregularis  actually represent a single species.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the contact of the Tallahatta and Lisbon formations at site ACh-14, the basal Lisbon Formation at site ACov-11, the contact of the Lisbon Formation and Gosport Sand at site AMo-4, and the Gosport Sand at site ACh-21. Lower Lutetian to middle Bartonian, zones NP14 to NP17.

Kingdom

Animalia

Phylum

Chordata

Class

Elasmobranchii

Order

Myliobatiformes

Family

Myliobatidae

Genus

Aetobatus

Loc

Aetobatus sp

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L. 2019
2019
Loc

Aetiobatis sp. cf. A. irregularis – Thurmond & Jones 1981: 75

Thurmond J. T. & Jones D. E. 1981: 75
Loc

Aetobatis sp.

Holman J. A. & Case G. R. 1988: 328
Loc

Aetobatus irregularis – Cappetta & Case 2016: 66

Cappetta H. & Case G. R. 2016: 66