title: Musculoskeletal system of the neck of the polar bear (Ursus maritimus) and the Malayan bear (Helarctos malayanus).
abstract: The gross anatomical study was undertaken in the musculoskeletal system of the neck of the polar bear, and the findings were compared with those of the Malayan bear. The Musculus splenius and the M. trapezius were well-developed in the polar bear. The long neck of the polar bear consisted mainly of the M. splenius with the M. biventer cervicis and the M. complexus lying tightly underneath. The cervical vertebrae possessed huge ventral tubercle in the ventral part of the transverse process in the polar bear. These morphological characteristics suggest that the polar bear may rotate and bend the skull and the long cervical vertebrae. We postulate that the polar bear has evolved the high-mobility long neck to adapt for swimming. Unlike the polar bear, the Malayan bear has not specialized in the neck structure.
authors.affiliation: Department of Zoology, National Science Museum, Tokyo, Japan. endo@bakaku.go.jp
authors.forename: H
authors.initials: H
authors.lastname: Endo
authors.forename: Y
authors.initials: Y
authors.lastname: Kakegawa
authors.forename: H
authors.initials: H
authors.lastname: Taru
authors.forename: M
authors.initials: M
authors.lastname: Sasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Arishima
mesh_terms: D000818:Animals; D002574:Cervical Vertebrae / Q000033:anatomy & histology* / Q000502:physiology; D009333:Neck; D009334:Neck Muscles / Q000033:anatomy & histology* / Q000502:physiology; D012886:Skull / Q000033:anatomy & histology; D013045:Species Specificity; D013550:Swimming; D001503:Ursidae / Q000033:anatomy & histology* / Q000502:physiology