''Archaeostylus manukauensis'' is an extinct

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

flax snail ''Placostylus'', or flax snails, are a genus of very large, air-breathing land snails, terrestrial pulmonate gastropod molluscs in the family Bothriembryontidae.MolluscaBase eds. (2020). MolluscaBase. Placostylus H. Beck, 1837. Accessed through: ...

, a large air-breathing land snail, a

terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...

pulmonate gastropod mollusc in the family

Bothriembryontidae Bothriembryontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Orthalicoidea. Taxonomy This family has been named Placostylidae and had no subfamilies (according to the taxonomy of ...

. MolluscaBase eds. (2022). MolluscaBase. Archaeostylus Brook & Hayward, 2022 †. Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1582263 on 2022-06-19 This species is the typetaxon and only member of the monotypic genus ''Archaeostylus'', found in

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...

. ''Archaeostylus'' is thought to represent an extinct, sister lineage to the modern flax snail species currently living in New Zealand, and is not a direct ancestor.

Description

''Archaeostylus manukauensis'' has a large long

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

that is thin, elongate-conical, and slightly dorso-ventrally compressed. Unlike other genera of

, ''A. manukauensis'' lacks a thickened outer lip surrounding its aperture, and instead possesses a thin peristome with a collabral callus ridge on the palatal wall. In all of the specimens studied, a broad, shelf-like callus ridge extends from top of aperture almost to the base of the columella, bearing a flattened, irregularly rounded, tongue-like projection on its upper part.

Distribution and habitat

Fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

of this extinct land snail species are known only from a Late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Waipipian While also using the international geologic time scale, many nations–especially those with isolated and therefore non-standard prehistories–use their own systems of dividing geologic time into epochs and faunal stages. In New Zealand, these ep ...

(~3.6–3.0 Ma) marine shellbed deposit ( Kaawa Formation) located approximately 30 m below the suburb of Mangere,

Auckland Auckland (pronounced ) ( mi, Tāmaki Makaurau) is a large metropolitan city in the North Island of New Zealand. The most populous urban area in the country and the fifth largest city in Oceania, Auckland has an urban population of about I ...

. It is currently regarded as one of the two oldest known flax snails species represented in the fossil record, along with a single specimen of a second species ('' Maoristylus pliocenica'') also discovered from the Kaawa Formation at Mangere. ''A. manukauensis'' presumably inhabited lowland broadleaf forest and scrub habitats, similar to recent species of flax snail. Its buoyant shells likely ended up in marine shellbed deposits after being washed to the coast in streams, or in run-off after heavy rainfall.

References

{{reflist, refs= Brook F.J. and Hayward B.W. (2022). Taxonomy and taphonomy of Pliocene bulimoid land snails from Māngere, northern New Zealand, with descriptions of a new genus and two new species (Gastropoda: Bothriembryontidae: Placostylinae). ''New Zealand Journal of Geology and Geophysics'' https://doi.org/10.1080/00288306.2022.2072904 Bothriembryontidae Gastropod genera