Giant Mandarina Snail (Mandarina titan)  

This species was described in 1989 based on fossil and subfossil material that had been collected from the fissure deposits of Minamijima Island, Ogasawara Islands, Japan. [1]

The Giant Mandarina Snail was indeed a giant, its shells reached sizes of up to nearly 7 to 8 cm in diameter, making it the largest land snail species of the Ogasawara Islands and also of Japan. [2]

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The species first appeared about 13000 BCE and finally disappeares from the deposits at around 8000 BCE in the early Holocene, it disappeared due to natural environmental changes. [1] 

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References:  

[1] Satoshi Chiba: Taxonomy and morphologic diversity of Mandarina (Pulmonata) in the Bonin Islands. Transactions and Proceedings – Palaeontological Society of Japan 155: 218-251. 1989
[2] Satoshi Chiba: Taxonomic revision of the fossil land snail species of the genus Mandarina in the Ogasawara Islands. Paleontological Research 11(4): 317-329. 2007

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edited: 19.04.2019