This site is authoritative because it is the website of a shark research center. The publisher is also the webmaster of the site. The author does not state any credentials on the website but by doing some research I found that he is a biologist. The publisher does not try to sell anything on this site. Last the publisher is a professional research center.
Authority
http://www.flmnh.ufl.edu/fish/Gallery/Descript/PelagicThresher/PelagicThresher.html
MLA
Seitz, Jason. ufl.edu. FLMNH. 29 August 2011
This site is authoritative because it is the website of a shark research center. The publisher is also the webmaster of the site. The author does not state any credentials on the website but by doing some research I found that he is a biologist. The publisher does not try to sell anything on this site. Last the publisher is a professional research center.