We describe two well-preserved mandibles of Stegolophodon pseudolatidens (Mammalia, Proboscidea, Stegodontidae) discovered from the lower Miocene (ca. 16.9–16.6 Ma) in Northeast Japan. The mandible of Sl. pseudolatidens is primitive within the Stegodontidae in having a short symphysis with lower tusks, tetralophodont lower molars, and a mandibular canal with the large dorsoventral diameter in the anterior segment. It is characterized by a perpendicular mandibular ramus (forming an almost right angle between the anterior margin of the mandibular ramus and the dorsal horizontal surface of the corpus), and many scratches in mesial direction on the occlusal surface of m3, implying that Sl. pseudolatidens appears to have acquired a proal jaw movement during mastication. While the mandibular morphology of Sl. pseudolatidens is comparable to that of other species of the genus that of Stegolophodon cf. stegodontoides from the upper Miocene of Myanmar differs from that of these species in having a shorter symphysis, which is a derived condition.
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1 July 2021
Mandibular Morphology of Stegolophodon pseudolatidens (Proboscidea, Stegodontidae) from the Lower Miocene of Japan
Katsunori Iizumi,
Hisao Ando,
Kunihiro Suzuki,
Yoshiki Koda
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Paleontological Research
Vol. 25 • No. 3
July 2021
Vol. 25 • No. 3
July 2021
Early Miocene
mandible
Natori Group
Shirado Group
Stegodontidae
Stegolophodon