''Archaeostylus manukauensis'' is an extinct

species In biology, a species is the basic unit of 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 the appropriate s ...

of flax snail, a large air-breathing

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as ...

, 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 Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includ ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

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 th ...

. 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 smaller islands. It is the sixth-largest island count ...

. ''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 ou ...

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

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 (~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 List of New Zealand urban areas by population, most populous urban area in the country and the List of cities in Oceania by po ...

. 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