Archaeostylus
Temporal range: Late Pliocene (Waipipian)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Order: Stylommatophora
Family: Bothriembryontidae
Genus: †Archaeostylus
Species:
†A. manukauensis
Binomial name
†Archaeostylus manukauensis
Brook and Hayward, 2022[1]

Archaeostylus manukauensis is an extinct species of flax snail, a large air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Bothriembryontidae. [2]

This species is the typetaxon and only member of the monotypic genus Archaeostylus, found in Pliocene age sediments of northern New Zealand. 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.[1]

Description

Archaeostylus manukauensis has a large 60.2–70.4 millimetres or 2.37–2.77 inches long shell that is thin, elongate-conical, and slightly dorso-ventrally compressed.[1] 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 of this extinct land snail species are known only from a Late Pliocene/Waipipian (~3.6–3.0 Ma) marine shellbed deposit (Kaawa Formation) located approximately 30 m below the suburb of Mangere, Auckland.[1][3] 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.[4] 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

  1. 1 2 3 4 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
  2. ↑ 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
  3. ↑ Hayward, B.W. (2021). "Once-in-a-Lifetime Fossil Digs at Mangere Sewage Works". Geoscience Society of New Zealand Newsletter (33): 46–49.
  4. ↑ "Flax snail/pupurangi". Department of Conservation. Retrieved June 17, 2022.
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