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Journal of Paleontology

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Late Cretaceous Octobrachiate Coleoid Lower Jaws from the North Pacific Regions

¹ Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan, <tanabe{at}eps.s.u-tokyo.ac.jp>
² Courtenay and District Museum and Paleontology Center, Courtenay, British Columbia V9N 1G7, Canada, <museum{at}island.net>
³ Nakagawa Museum of Natural History, Nakagawa Town, Hokkaido 098-2626, Japan, <nmhikida{at}coral.ocn.ne.jp>

Eight well-preserved cephalopod jaw fossils were discovered from the Upper Cretaceous (Santonian and Campanian) deposits of Vancouver Island, Canada, and Hokkaido, Japan. They occur individually in calcareous concretions and retain their three-dimensional architecture. Seven of them consist of a widely open outer lamella and a posteriorly projected inner lamella with a pointed rostrum. Both lamellae are made of fluorapatite, which may represent diagenetically altered chitin, and lack a calcareous element. Based on these diagnostic features, the seven jaw fossils are identified as lower jaws of the Coleoidea. Comparison with the lower jaws of modern coleoids allows us to distinguish the following new genera and species among them; Nanaimoteuthis jeletzkyi of the Order Vampyromorphida, and Paleocirroteuthis haggarti and P. pacifica of the Order Cirroctopodida. The lower jaws of these new taxa are clearly distinguished by having a much less projected inner lamella from those of modern and extinct species of the Superorder Decabrachia and the Order Octopodida. The maximum lengths of their outer lamellae (35.0–67.1 mm) are much larger than those of most modern vampyromorph and cirroctopodid species, indicating the large body size and weight of their owners. One of the other three lower jaws examined, characterized by a posteriorly extended outer lamella, may be assigned to the Octopodida. This study clearly demonstrates that large octobrachiate coleoids existed in the Late Cretaceous North Pacific.