To resolve mystery of convergent evolution of secondary symmetrical skull in Odontoceti: using structures of the inner ear

2015 Fiscal Year Final Research Report

• Project/Area Number: 26800268
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Stratigraphy/Paleontology
• Research Institution: Waseda University
• Principal Investigator: Murakami Mizuki 早稲田大学, 教育・総合科学学術院, 助手 (70710614)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: ハクジラ類 / 頭骨の二次的な左右対称性の進化 / 内耳構造

Outline of Final Research Achievements

Micro CT scanning of fossil odontocete periotics and reconstruction of the zone of audibility could not carry out several reasons. However, cranial asymmetry of both extant and extinct odontocetes in many museums are measured quantitatively (16 families, 37 genera, 53 species). As a result, examinations revealed following points: (1) deviation of bones from the sagittal line and size differences between left and right bones do not always show same trend; (2) from deviation of bones from the sagittal line and size differences between left and right bones, secondary cranial symmetry in Phocoenidae evolved; (3) to compare other odontocetes, right nasal of Delphinidae significantly is larger than its left nasal; (4) Ziphius and Mesoplodon carlhubbsi show strong cranial asymmetry in Ziphiidae.

Free Research Field

層位・古生物学