Overview of stratigraphy and paleontology of Pliocene Tonohama Group, Kochi Prefecture, southwest Japan

Iwai, Masao; Kondo, Yasuo; Kikuchi, Naoki; Oda, Masayuki

doi:10.5575/geosoc.112.s27

Cited by 6 publications

(2 citation statements)

References 26 publications

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“…6; Ishizaki, 1983; c . 3 Ma, fide Iwai et al ., 2006). Therefore, it is still difficult to specify which is the ancestral species on the sole basis of their fossil records.…”

Section: Discussionmentioning

confidence: 99%

Taxonomy and sexual dimorphism of a new species of Loxoconcha (Podocopida: Ostracoda) from the Pleistocene of the Japan Sea

Ozawa¹,

Ishii²

2008

Zool J Linn Soc

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A new ostracod, Loxoconcha kamiyai sp. nov. in the Family Loxoconchidae, is described from the Pleistocene Omma Formation of Japan. Its geological and geographical distributions suggest that this species was once endemic to the Japan Sea, where it would have evolved until the Pliocene. Since the early Pleistocene, this species would have become extinct within this marginal sea during glacial maxima, probably due to its narrower salinity tolerances and geographical distributions than those of extant species inhabiting the euryhaline environments in other seas. The distributional patterns of pore systems in this species strongly suggest its closest phylogenetic affinities to a living species, Loxocorniculum mutsuense. These two species show a unique adult sexual dimorphism in the anterior element of the hingement. Taking the female hingement morphology as a standard, the male hingement can be explained in terms of heterochrony, i.e. paedomorphosis. Sexual hingement dimorphism with paedomorphosis occurs in only one phylogenetic group of the genus Loxoconcha, which is distinguished by the ontogenetic distributional patterns of pore systems. This morphology may represent relict primitive characters of ancient ostracods and could be an important character for evaluating the history of sexual dimorphism in ostracods since the Palaeozoic.

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“…6; Ishizaki, 1983; c . 3 Ma, fide Iwai et al ., 2006). Therefore, it is still difficult to specify which is the ancestral species on the sole basis of their fossil records.…”

Section: Discussionmentioning

confidence: 99%

Taxonomy and sexual dimorphism of a new species of Loxoconcha (Podocopida: Ostracoda) from the Pleistocene of the Japan Sea

Ozawa¹,

Ishii²

2008

Zool J Linn Soc

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“…Several bivalves (e.g., Clementia vatheleti Mabille, 1901) occur in life positions in the same horizon. The depositional environment is interpreted as the distal part of an inner shelf or the proximal part of an outer shelf (Iwai et al, 2006). In addition to the fossil material, Recent specimens of Truncatoflabellum spp.…”

Section: Methodsmentioning

confidence: 99%

Asexual reproduction of Pliocene solitary scleractinian coralTruncatoflabellum: a morphological and biometric study

Tokuda

Ezaki

2012

J. Paleontol.

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Truncatoflabellumhas been considered a free-living genus that exhibits both sexual and asexual phases; divided lower coralla (anthocauli) are specialized for asexual reproduction by transverse division through a decalcification process, whereas the upper coralla (anthocyathi) only undertake sexual reproduction, in a life-cycle strategy that includes a distinct alternation of generations. However, little evidence has been presented to support this idea of its life cycle. We elucidate the life mode ofTruncatoflabellumby identifying key fossil characters (e.g., multiple rejuvenations and decalcification records just beneath lateral spines) and statistically analyzing the size distributions of over 500 individual coralla. Results of those morphological and biometric analyses clearly indicate alternation of generations in the life cycle ofTruncatoflabellum.

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Late Quaternary uplift rate inferred from marine terraces, Muroto Peninsula, southwest Japan: Forearc deformation in an oblique subduction zone

Matsu’ura

2015

Geomorphology

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Overview of stratigraphy and paleontology of Pliocene Tonohama Group, Kochi Prefecture, southwest Japan

Cited by 6 publications

References 26 publications

Taxonomy and sexual dimorphism of a new species of Loxoconcha (Podocopida: Ostracoda) from the Pleistocene of the Japan Sea

Taxonomy and sexual dimorphism of a new species of Loxoconcha (Podocopida: Ostracoda) from the Pleistocene of the Japan Sea

Asexual reproduction of Pliocene solitary scleractinian coralTruncatoflabellum: a morphological and biometric study

Late Quaternary uplift rate inferred from marine terraces, Muroto Peninsula, southwest Japan: Forearc deformation in an oblique subduction zone

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