New fossil remains from the pliocene koetoi formation of northern japan provide insights into growth rates and the vertebral evolution of porpoises

Mizuki Murakami, Chieko Shimada, Yoshinori Hikida, Hiromichi Hirano

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Extant porpoises (Phocoenidae) are odontocetes characterized by their small size, short and wide rostrum, late (or absent) completion of epiphyseal ankylosis in the vertebral column (= physical maturity), and short life cycles, all of which are thought to have resulted from progenetic evolution. We describe a small fossil phocoenid from the lower Pliocene Koetoi Formation of Hokkaido (northern Japan), preserving a small, narrow rostrum, as well as anteroposteriorly elongate thoracic and lumbar vertebral centra with completely fused epiphyses. Physical maturity in this specimen occurred significantly earlier than in extant phocoenids, as shown by dental data indicating that the specimen died at only four years of age. The difference between the present material and extant porpoises may be attributable to different growth rates during ontogeny. The long centra and caudally inclined neural spines of the specimen from Hokkaido are primitive characters among phocoenids. By contrast, the great height of its neural spines is highly derived, even among extant species, and suggestive of a fast swimmer. In terms of its vertebral morphology, the new specimen falls within a morphological continuum defined by the archaic Numataphocoena yamashitai and the highly derived vertebral morphology of Phocoenoides dalli. Phocoenid vertebral evolution has been complex and frequently convergent, as opposed to stepwise and unidirectional. The different vertebral morphologies of the new specimen and the contemporaneous extinct taxa Numataphocoena and Piscolithax longirostris indicate that they were adapted to different environments.

    Original languageEnglish
    Pages (from-to)97-111
    Number of pages15
    JournalActa Palaeontologica Polonica
    Volume60
    Issue number1
    DOIs
    Publication statusPublished - 2015 Mar 1

    Fingerprint

    porpoise
    Pliocene
    fossil
    ontogeny
    life cycle

    Keywords

    • age estimation
    • growth rate
    • Japan
    • Mammalia
    • Phocoenidae
    • Pliocene
    • vertebral evolution

    ASJC Scopus subject areas

    • Palaeontology

    Cite this

    New fossil remains from the pliocene koetoi formation of northern japan provide insights into growth rates and the vertebral evolution of porpoises. / Murakami, Mizuki; Shimada, Chieko; Hikida, Yoshinori; Hirano, Hiromichi.

    In: Acta Palaeontologica Polonica, Vol. 60, No. 1, 01.03.2015, p. 97-111.

    Research output: Contribution to journalArticle

    Murakami, Mizuki ; Shimada, Chieko ; Hikida, Yoshinori ; Hirano, Hiromichi. / New fossil remains from the pliocene koetoi formation of northern japan provide insights into growth rates and the vertebral evolution of porpoises. In: Acta Palaeontologica Polonica. 2015 ; Vol. 60, No. 1. pp. 97-111.
    @article{002e9507d63541fc9d38ba0ec5340e89,
    title = "New fossil remains from the pliocene koetoi formation of northern japan provide insights into growth rates and the vertebral evolution of porpoises",
    abstract = "Extant porpoises (Phocoenidae) are odontocetes characterized by their small size, short and wide rostrum, late (or absent) completion of epiphyseal ankylosis in the vertebral column (= physical maturity), and short life cycles, all of which are thought to have resulted from progenetic evolution. We describe a small fossil phocoenid from the lower Pliocene Koetoi Formation of Hokkaido (northern Japan), preserving a small, narrow rostrum, as well as anteroposteriorly elongate thoracic and lumbar vertebral centra with completely fused epiphyses. Physical maturity in this specimen occurred significantly earlier than in extant phocoenids, as shown by dental data indicating that the specimen died at only four years of age. The difference between the present material and extant porpoises may be attributable to different growth rates during ontogeny. The long centra and caudally inclined neural spines of the specimen from Hokkaido are primitive characters among phocoenids. By contrast, the great height of its neural spines is highly derived, even among extant species, and suggestive of a fast swimmer. In terms of its vertebral morphology, the new specimen falls within a morphological continuum defined by the archaic Numataphocoena yamashitai and the highly derived vertebral morphology of Phocoenoides dalli. Phocoenid vertebral evolution has been complex and frequently convergent, as opposed to stepwise and unidirectional. The different vertebral morphologies of the new specimen and the contemporaneous extinct taxa Numataphocoena and Piscolithax longirostris indicate that they were adapted to different environments.",
    keywords = "age estimation, growth rate, Japan, Mammalia, Phocoenidae, Pliocene, vertebral evolution",
    author = "Mizuki Murakami and Chieko Shimada and Yoshinori Hikida and Hiromichi Hirano",
    year = "2015",
    month = "3",
    day = "1",
    doi = "10.4202/app.2012.0127",
    language = "English",
    volume = "60",
    pages = "97--111",
    journal = "Acta Palaeontologica Polonica",
    issn = "0567-7920",
    publisher = "Polska Akademia Nauk",
    number = "1",

    }

    TY - JOUR

    T1 - New fossil remains from the pliocene koetoi formation of northern japan provide insights into growth rates and the vertebral evolution of porpoises

    AU - Murakami, Mizuki

    AU - Shimada, Chieko

    AU - Hikida, Yoshinori

    AU - Hirano, Hiromichi

    PY - 2015/3/1

    Y1 - 2015/3/1

    N2 - Extant porpoises (Phocoenidae) are odontocetes characterized by their small size, short and wide rostrum, late (or absent) completion of epiphyseal ankylosis in the vertebral column (= physical maturity), and short life cycles, all of which are thought to have resulted from progenetic evolution. We describe a small fossil phocoenid from the lower Pliocene Koetoi Formation of Hokkaido (northern Japan), preserving a small, narrow rostrum, as well as anteroposteriorly elongate thoracic and lumbar vertebral centra with completely fused epiphyses. Physical maturity in this specimen occurred significantly earlier than in extant phocoenids, as shown by dental data indicating that the specimen died at only four years of age. The difference between the present material and extant porpoises may be attributable to different growth rates during ontogeny. The long centra and caudally inclined neural spines of the specimen from Hokkaido are primitive characters among phocoenids. By contrast, the great height of its neural spines is highly derived, even among extant species, and suggestive of a fast swimmer. In terms of its vertebral morphology, the new specimen falls within a morphological continuum defined by the archaic Numataphocoena yamashitai and the highly derived vertebral morphology of Phocoenoides dalli. Phocoenid vertebral evolution has been complex and frequently convergent, as opposed to stepwise and unidirectional. The different vertebral morphologies of the new specimen and the contemporaneous extinct taxa Numataphocoena and Piscolithax longirostris indicate that they were adapted to different environments.

    AB - Extant porpoises (Phocoenidae) are odontocetes characterized by their small size, short and wide rostrum, late (or absent) completion of epiphyseal ankylosis in the vertebral column (= physical maturity), and short life cycles, all of which are thought to have resulted from progenetic evolution. We describe a small fossil phocoenid from the lower Pliocene Koetoi Formation of Hokkaido (northern Japan), preserving a small, narrow rostrum, as well as anteroposteriorly elongate thoracic and lumbar vertebral centra with completely fused epiphyses. Physical maturity in this specimen occurred significantly earlier than in extant phocoenids, as shown by dental data indicating that the specimen died at only four years of age. The difference between the present material and extant porpoises may be attributable to different growth rates during ontogeny. The long centra and caudally inclined neural spines of the specimen from Hokkaido are primitive characters among phocoenids. By contrast, the great height of its neural spines is highly derived, even among extant species, and suggestive of a fast swimmer. In terms of its vertebral morphology, the new specimen falls within a morphological continuum defined by the archaic Numataphocoena yamashitai and the highly derived vertebral morphology of Phocoenoides dalli. Phocoenid vertebral evolution has been complex and frequently convergent, as opposed to stepwise and unidirectional. The different vertebral morphologies of the new specimen and the contemporaneous extinct taxa Numataphocoena and Piscolithax longirostris indicate that they were adapted to different environments.

    KW - age estimation

    KW - growth rate

    KW - Japan

    KW - Mammalia

    KW - Phocoenidae

    KW - Pliocene

    KW - vertebral evolution

    UR - http://www.scopus.com/inward/record.url?scp=84924995763&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84924995763&partnerID=8YFLogxK

    U2 - 10.4202/app.2012.0127

    DO - 10.4202/app.2012.0127

    M3 - Article

    VL - 60

    SP - 97

    EP - 111

    JO - Acta Palaeontologica Polonica

    JF - Acta Palaeontologica Polonica

    SN - 0567-7920

    IS - 1

    ER -