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A new species of Stegodon (Mammalia, Proboscidea) from the Kazusa Group (lower Pleistocene), Hachioji City, Tokyo, Japan and its evolutionary morphodynamics
Author(s) -
AIBA HIROAKI,
BABA KATSUYOSHI,
MATSUKAWA MASAKI
Publication year - 2010
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/j.1475-4983.2010.00953.x
Subject(s) - proboscidea , pleistocene , geology , group (periodic table) , paleontology , lineage (genetic) , early pleistocene , beach morphodynamics , biology , biochemistry , chemistry , organic chemistry , gene , sediment transport , sediment
Stegodon protoaurorae sp. nov. (Proboscidea) from the lower Pleistocene Terada Formation of the Kazusa Group in Japan is proposed as a new species based on characteristic features of plate formula, molar size, tooth enamel and plate frequency, and is described herein. The specimen of the new species was transported by autumn storms and buried. The new species fills an evolutionary gap between S. miensis and S. aurorae . Speciation in the lineage from S. miensis through S. protoaurorae to S. aurorae is inferred to have been caused by reduction of terrestrial space during marine transgression. The biostratigraphic distribution of S. protoaurorae suggests intercalation of a new S . protoaurorae Zone between the S . miensis Zone and the S . aurorae Zone. The S . protoaurorae Zone can be defined in the Nakatsu Group and the Terada Formation of the Kazusa Group, and can be assigned an age of 2.9–2.1 Ma.