A new fossil megamouth shark (Lamniformes, Megachasmidae) from the Oligocene-Miocene of the western United States

ABSTRACTThe extant megamouth shark, <i>Megachasma pelagios</i> (Lamniformes: Megachasmidae), is a large filter-feeding fish. We here describe a new species of <i>Megachasma</i>, <i>M. applegatei</i>, sp. nov., a putative sister species of the extant <i>M. pelagios</i>, based on isolated teeth from late Oligocene–early Miocene (late Chattian–Aquitanian) marine deposits in California and Oregon, U.S.A. Although showing a megachasmid tooth design, teeth of <i>M. applegatei</i>, sp. nov., exhibit a wide morphological range and are reminiscent to those of odontaspidid sharks with strong heterodonty. <i>Megachasma applegatei</i>, sp. nov., could have commonly measured approximately 6 m in total length and likely had a wide range of diet, possibly including small fishes and planktonic invertebrates. The fossil record indicates that either <i>M. applegatei</i>, sp. nov., was broadly adapted to a wide bathymetric tolerance or was a nektopelagic feeder over both deep and shallow water habitats. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP.