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Ptychodus
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<p><i>Ptychodus</i> is a genus of extinct large <a href="/facts/Durophagy/hcWxSxJv">durophagous</a> (shell-crushing) <a href="/facts/Lamniformes/VFrPGhlJ">lamniform</a> <a href="/facts/Shark/gnS0bGPW">sharks</a> from the <a href="/facts/Cretaceous/nwKtFtKx">Cretaceous</a> period, spanning from the <a href="/facts/Albian/faHcmHDC">Albian</a> to the <a href="/facts/Campanian/MoPSxcqL">Campanian</a>. Fossils of <i>Ptychodus</i> teeth are found in many Late Cretaceous marine sediments worldwide. </p><p>At least 16 species are considered valid, with the largest members of the genus suggested to have grown up to 10 meters (33 feet) long. The youngest remains date to around 75 <a href="/facts/Million_years_ago/DXcnXuAw">million years ago</a>. A large number of remains have been found in the former <a href="/facts/Western_Interior_Seaway/I4AKChV9">Western Interior Seaway</a>. </p>