25 Foot Long "Chainsaw" Shark Reconstructed
The terrifying 25 foot long prehistoric shark with a 'spiral'
of teeth that worked like a CHAINSAW (Helicoprion had a
conveyor belt of jagged teeth that spiralled out of its lower
jaw and ripped prey to shreds), Mail Online
Prehistoric ghost shark Helicoprion's spiral-toothed jaw
explained, Scientific American, Feb 27, 2013
Helicoprion: Scientists solve mysteries of ancient 'shark'
with spiral-toothed jaw, PhysOrg, February 27, 2013
The paper is:
Tapanila, L., J. Pruitt, A. Pradel, C. D. Wilga, J. B. Ramsay,
R. Schlader, and D. A. Didier, 2013, Jaws for a spiral-tooth
whorl: CT images reveal novel adaptation and phylogeny
in fossil Helicoprion. Biology Letters, vol. 9, no. 2,
article 20130057. http://rsbl.royalsocietypublishing.org/content/9/2/20130057.full.pdf+html