Walden’s Callina Snail was described in 2018 during a genus revision including many Madeiran land snail forms; it is known only from subfossil shells that were recovered from Holocene deposits near the southern coast of Porto Santo in the Madeiran archipelago in the Atlantic Ocean.

The shells reach sizes of around 1,57 cm in diameter; they are whitish (probably bleached) and have a closed umbilicus and a well-rounded rather than angulated or keeled last whorl.

The species disappeared before the island’s scientific exploration in the 19th century, maybe even due to natural causes like slight, local (non-human induced) climatical changes. [1]

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References:

[1] Willy De Mattia; Marco T. Neiber; Klaus Groh: Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geometridae). ZooKeys 732: 1-125. 2018

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Photo from: ‘Willy De Mattia; Marco T. Neiber; Klaus Groh: Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geometridae). ZooKeys 732: 1-125. 2018’

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edited: 24.08.2022