This species was described in 2018 during a genus-group revision; it is known only from subfossil material which was collected from near the northern shore of Porto Santa.
The species apparently was already extinct when before the island was scientifically explored. [1]
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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’
[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
This species was described in 2018; it is known only from subfossil shells that were found in deposits near the south-eastern shores of Porto Santo, Madeira.
The species disappeared before the scientific exploration of the island. [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’
Ripken’s Wollastonia Snail was described in 2018 during a genus-group revision; it is known only from subfossil material that was found near the south-eastern shore of Porto Santo, Madeira.
The species died out before the scientific exploration of the island, maybe even before the first humans arrived. [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’
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’
This species was described in 2018, it is known only from the southeastern coast of Porto Santo.
The shells reach a size of about 0,5 to 0,56 cm in diameter.
The species appears to have already been extinct before the scientific exploration of the island in the 19th century. [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’
This species was described in 1867, originally as a kind of a subspecies or variety of another species, Wollastonia vermetiformis (R. T. Lowe), or as a fossil form of a closely related recent species, Hystricella bicarinata (G. B. Sowerby) respectively.
The Small Hystricella Snail is known from several Quaternary mud deposits along the southeastern coast of Porto Santo, Madeiran Islands, Portugal.
The distinctly dome-shaped shells reach sizes of 0,5 to 0,6 cm in diameter. [1]
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The Small Hystricella Snail disappeared before the scientific exploration of Porto Santo in the 19th century, it probably died out due to natural changes in the microclimate of its habitat.
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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, Geomitridae). ZooKeys 732: 1-125. 2018
Keeled Wollastonia Snail (Wollastonia subcarinulata)
The Keeled Wollastonia Snail is known exclusively from Quaternary deposits along the southeastern coast of Porto Santo, Madeiran Islands, Portugal.
The species was described in 1878, originally as a kind of subspecies or variety of another species, Wollastonia oxytropis (R. T. Lowe), of which it differs by its larger size beside some other features like a more distinctly marked suture, the finer granulation, and the wider aperture. [1]
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The Keeled Wollastonia Snail disappeared before the scientific exploration of Porto Santo in the 19th century, it probably died out due to changes in the microclimate of its habitat.
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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, Geomitridae). 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’
The Madeiran Geomitra Snail, which was endemic to the island of Madeira, was discovered and apparently also described in 1860. It appears to be known exclusively from fresh but empty shells as well as from numerous subfossil and fossil specimens from both Pleistocene and Holocene deposits. [2]
The shells reached sizes of about 1,75 cm in diameter, they were rather this and fragile in substance, extremely roughened, perfectly opaque, flattened, rounded and planorbiform, with the spire greatly depressed and its umbilicus excessively wide and open, and of a uniform dull pale-brownish flesh-color varying into a chalky white. [1]
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The following citation is from T. Vernon Wollaston (1878) and tells a bit about the species.:
“This is not only one of the most anomalous of the Madeiran Helices, but by far the most remarkable one which has been brought to light of late years, – it having been discovered, by Mr. Lowe, so recently as in 1860. It was at an elevation of about 4000 feet [ca. 1219 m], in the Ribeira do Fayal, that Mr. Lowe met with it, and moreover in considerable abundance, -‘on the surface of the somewhat moist, loose, friable, black vegetable mould, amongst tufts of grasses, ferns, etc., on a steep, dry, sunny bank clothed with shrubs of Vaccinium and Heath, and mixed with a few scattered trees of Laurus, at the foot of perpendicular crags, along the new Levada called the Levada da Fajãa dos Vinhaticos [Levada da Fajã dos Vinháticos aka. Levadinha Joao de Deus].‘” [1]
The locality, mentioned in the citation above, could never be relocated.
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The species disappeared at around 1620 AD.. [2]
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References:
[1] T. Vernon Wollaston: Testacea Atlantica: or the Land and Freshwater Shells of the Azores, Madeiras, Salvages, Canaries, Cape Verdes, and Saint Helena. London: L. Reeve & Co. 1878 [2] Glenn A. Goodfriend; R. A. D. Cameron; L. M. Cook: Fossil evidence of recent human impact on the land snail fauna of Madeira. Journal of Biogeography 21: 309-320. 1994
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Depictions from: ‘George W. Tryon; Henry A. Pilsbry; a.o.: Manual of Conchology. Second Series: Pulmonata Vol. 4, Helicidae Vol. 2. 1888’
