Paleogene origin of planktivory in the Batoidea

ABSTRACT

The planktivorous mobulid rays are a sister group to, and descended from, rhinopterid and myliobatid rays that possess a dentition showing adaptations consistent with a specialized durophagous diet. Within the Paleocene and Eocene, there are several taxa that display dentitions apparently transitional between these extreme trophic modalities, in particular the genus Burnhamia. The holotype of Burnhamia daviesi was studied through X-ray computed tomography (CT) scanning. Digital renderings of this incomplete but articulated jaw and dentition revealed previously unrecognized characters regarding the jaw cartilages and teeth. In addition, the genus Sulcidens, gen. nov., is erected for articulated dentitions from the Paleocene previously assigned to Myliobatis. Phylogenetic analyses confirm Burnhamia as a sister taxon to the mobulids and the Mobulidae as a sister group to Rhinoptera. Shared dental characters between Burnhamia and Sulcidens likely represent independent origins of planktivory within the rhinopterid-myliobatid clade. The transition from highly specialized durophagous feeding morphologies to the morphology of planktivores is perplexing but was facilitated by a pelagic swimming mode in these rays and, we propose, through subsequent transition from either meiofauna-feeding or pelagic fish-feeding to pelagic planktivory.

http://zoobank.org/urn:lsid:zoobank.org:pub:511E9C39-1208-4F56-8DC1-2B92D2EDB4B3

Citation for this article: Underwood, C. J., M. A. Kolmann, and D. J. Ward. 2017. Paleogene origin of planktivory in the Batoidea. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1293068.

ACKNOWLEDGMENTS

We would like to thank M. Segaoui and V. Valle for their help in obtaining Moroccan fossils and J. Swenson for providing us with modern Rhinoptera specimens. We would also like to thank Z. Johanson and all of the staff at the NHM CT unit for scanning material and help with rendering of the specimens. The undergraduate project carried out by P. Siedlecki started this research, and we especially would like to thank him. We are also grateful for funding from School of Graduate Studies Travel Grant and Ontario Trillium Scholarship to M.A.K.