Myliobatidae indeter.

By Fin Lover

• July 29, 2023

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Myliobatiformes
Family: Indet.
Genus: Indet.
Species: Indet.
Author Citation Compagno, 1973

Geological Time Scale

Eon: Phanerozoic
Era: Cenozoic
Period: Paleogene
Sub Period: None
Epoch: Oligocene

Stratigraphy

Ashley Formation

Provenance

Collector: Erin Osborne
Date Collected: 05/31/2023
Acquired by: Field Collection

Dimensions

Length: 32 mm
Width: 32 mm
Thickness: 7 mm

Location

Summerville
South Carolina
United States

• mouthplate
• myliobatidae
• rays
• south carolina
• summervillle

Comments

The literature reviewed shares a common belief that the genus Myliobatis has been, and continues to be, used as a “catch-all” genus within the Myliobatidea family.  While the ray fossil record is extensive, incomplete specimens and a lack of sufficient extant material to compare it to has resulted in our inability to recognize generic differences in myliobatid dentitions.  While some authors were confident identifying specimens to the genus level (and even reassigning specimens previously identified as Myliobatis to another genus), most included the caveat that we lack the knowledge and material necessary to definitively identify these specimens. 

A communication with David Cicimurri has provided valuable insight into this find :  "As far as the taxon goes, I would identify it as “Aetomylaeus” sp., which is a type of eagle ray. I use quotes because, although the teeth look very much like those of modern Aetomylaeus, studies suggest that the genus had not evolved by the Oligocene, so we can’t call Oligocene species by that name. The species is either something in the lineage that leads to Aetomylaeus or is another taxon that convergently evolved a similar tooth shape and dental arrangement – wide symphyseal teeth flanked by several rows of elongated and diamond-shaped lateral teeth."

References:

Claeson, K. M., O'Leary, M. A., Roberts, E. M., Sissoko, F., Bouaré, M., Tapanila, L., ... & Gottfried, M. D. (2010). First Mesozoic record of the stingray Myliobatis wurnoensis from Mali and a phylogenetic analysis of Myliobatidae incorporating dental characters. Acta Palaeontologica Polonica, 55(4), 655-674.

Cicimurri, D. J., Knight, J. L., & Ebersole, J. A. (2022). Early Oligocene (Rupelian) fishes (Chondrichthyes, Osteichthyes) from the Ashley Formation (Cooper Group) of South Carolina, USA. PaleoBios, 39(1).

Cicimurri, D. J., & Knight, J. L. (2019). Late Eocene (Priabonian) elasmobranchs from the Dry Branch Formation (Barnwell Group) of Aiken County, South Carolina, USA. PaleoBios, 36.

Cicimurri, D. J., & Knight, J. L. (2009). Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, South Carolina, USA. Acta Palaeontologica Polonica, 54(4), 627-647.

Ray, C. E., & Bohaska, D. J. (2001). Geology and Paleontology of the Lee Creek Mine, North Carolina, III.

Villafaña, J. A., Marramà, G., Hernandez, S., Carrillo-Briceño, J. D., Hovestadt, D., Kindlimann, R., & Kriwet, J. (2019). The Neogene fossil record of Aetomylaeus (Elasmobranchii, Myliobatidae) from the southeastern Pacific. Journal of Vertebrate Paleontology, 39(1), e1577251.

Welton, B. J. (1980). Eocene neoselachians from the La Meseta Formation, Seymour Island, Antarctic Peninsula.

Also visit these websites:

https://www.app.pan.pl/article/item/app20080077.html (Chandler Bridge Fm.)

https://escholarship.org/uc/item/0xv324c8 (Ashley Formation)