Wednesday, October 26, 2016

[PaleoIchthyology • 2016] Bothriolepis rex • A New Large-bodied Species of Bothriolepis (Antiarchi) from the Upper Devonian of Ellesmere Island, Nunavut, Canada

Bothriolepis rex 
 Downs, Daeschler, Garcia & Shubin, 2016 

New material from the Upper Devonian (Frasnian) Nordstrand Point Formation of Ellesmere Island, Nunavut, Canada, represents the largest known species of antiarch and the first described from the Nordstrand Point Formation. Bothriolepis rex, sp. nov., is additionally remarkable for the thickness and compactness of its dermal skeletal plates. The new species is diagnosed by a preorbital recess with a horizontal rostral margin; the presence of a wide unornamented border surrounding the infraorbital sensory line; central sensory lines that meet the margin of the nuchal close to the lateral corners; a supraotic thickening that does not extend caudal to a transverse crista of the nuchal; and a tall lateral lamina of the anterior dorsolateral. The thick and compact armor of Bothriolepis rex, sp. nov., recalls that of the co-occurring Perscheia pulla and gives occasion to a physical and ecological review of dermal skeletal mass and density in large-bodied, bottom-dwelling organisms in nonmarine ecosystems during the Late Devonian.

Fossil bones from the skull of Bothriolepis rex and a line drawing of the head viewed from above. The large, thick bones create an armor with a single opening for the eyes. The mouth is on the lower surface of the skull, indicating a bottom-feeding lifestyle.
Photo by Valentina Garcia, drawing by Jason Downs. 


ANTIARCHI Cope, 1885

BOTHRIOLEPIS Eichwald, 1840

Bothriolepis sp. Elliott et al., 2004.

Holotype— NUFV 1192, nuchal plate (Fig. 3).

Etymology— From the Latin ‘rex,’ king, in reference to the large body size.

Type Locality and Horizon— NV2K11 site (N77 06.1630 W87 09.0640), Nordstrand Point Formation near Okse Bay on southern Ellesmere Island, Nunavut, Canada. Palynological data indicate a middle Frasnian age (Maclarenii zone of Embry and Klovan, 1976).

A rendition of what the Bothriolepis rex would have looked like in its natural habitat along with a comparison of its size to that of a T. rex and an average human being.
Art by Jason Poole/Academy of Natural Sciences. 

Jason P. Downs, Edward B. Daeschler, Valentina E. Garcia and Neil H. Shubin. 2016. A New Large-bodied Species of Bothriolepis (Antiarchi) from the Upper Devonian of Ellesmere Island, Nunavut, Canada.  Journal of Vertebrate Paleontology.  DOI: 10.1080/02724634.2016.1221833

A New ‘King’ — New, Gigantic, Ancient Armored Fish Discovered