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The spotted eagle ray, Aetobatus narinari, is a member of Myliobatidae. This clade includes many rays that eat hard prey, as well as the massive planktivore the manta ray. Myliobatids are known from the Upper Cretaceous onwards, and occur today in the Atlantic, Indian, and Pacific oceans.
The skeleton of Aetobatus exhibits many adaptations for eating hard prey, like clams and mussels. As is typical for cartilaginous fishes, its skeleton is composed of cartilage. The outer surface of each skeletal element is usually covered in a thin mineralized layer made up of tiny tiles called tesserae; these tiles are what allow us to image the skeleton using CT. The hard prey crushing stingrays have extra mineralization in the jaws in the form of thin calcified struts that support the tooth-bearing surface and prevent hard prey from denting the jaws (rather than the other way around). We scanned the upper and lower jaws of an adult Aetobatus narinari in order to quantify the extent of these supporting struts. The horn shark (Heterodontus francisci) is another cartilaginous fish that eats hard prey, but it does not have these struts.
About the Species
This specimen of Aetobatus narinari (University of Massachusetts #F10077) was collected in Puerto Rico. It was made available to The University of Texas High-Resolution X-ray CT Facility for scanning courtesy of Dr. Adam Summers of the Department of Ecology and Evolutionary Biology, University of California, Irvine. Funding for scanning was provided by the McDowell Foundation.
About this Specimen
The specimen was scanned by Richard Ketcham and Matthew Colbert on 16-17 December 1999 along the coronal axis for a total of 210 512x512 pixel slices for the lower jaw and 300 512x512 pixel slices for the upper jaw. Each slice is 0.25 mm thick, with an interslice spacing of 0.25 mm and a field of reconstruction of 133 mm. The dataset displayed was reduced for optimal Web delivery from the original, much higher resolution CT data.
Lovejoy, N. R. 1996. Systematics of myliobatid elasmobranchs: With emphasis on the phylogeny and historical biogeography of neotropical freshwater stingrays. Zoological Journal of the Linnean Society 117:207-257.
Summers, A. P. 2000. Stiffening the stingray skeleton - an investigation of durophagy in myliobatid stingrays (Chondrichthyes, Batoidea, Myliobatoidea). Journal of Morphology 243:113-126. (Article review by Henry Gee in Nature)
Summers, A. P., T. J. Koob, and E. L. Brainerd. 1998. Stingray jaws strut their stuff. Nature 395:450-451.
Aetobatus narinari on Fishbase
Aetobatus on elasmo.com
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