Plectostoma

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Liew T, Vermeulen J, Marzuki M, Schilthuizen M (2014) A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina. ZooKeys 393 : 1–107, doi. Versioned wiki page: 2014-03-25, version 43788, https://species-id.net/w/index.php?title=Plectostoma&oldid=43788 , contributors (alphabetical order): Pensoft Publishers.

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BibTeX:

@article{Liew2014ZooKeys393,
author = {Liew, Thor-Seng, Vermeulen, Jaap Jan, Marzuki, Mohammad Effendi bin AND Schilthuizen, Menno},
journal = {ZooKeys},
publisher = {Pensoft Publishers},
title = {A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina},
year = {2014},
volume = {393},
issue = {},
pages = {1--107},
doi = {10.3897/zookeys.393.6717},
url = {http://www.pensoft.net/journals/zookeys/article/6717/abstract},
note = {Versioned wiki page: 2014-03-25, version 43788, https://species-id.net/w/index.php?title=Plectostoma&oldid=43788 , contributors (alphabetical order): Pensoft Publishers.}

}

RIS/ Endnote:

TY - JOUR
T1 - A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina
A1 - Liew T, Vermeulen J, Marzuki M
A1 - Schilthuizen M
Y1 - 2014
JF - ZooKeys
JA -
VL - 393
IS -
UR - http://dx.doi.org/10.3897/zookeys.393.6717
SP - 1
EP - 107
PB - Pensoft Publishers
M1 - Versioned wiki page: 2014-03-25, version 43788, https://species-id.net/w/index.php?title=Plectostoma&oldid=43788 , contributors (alphabetical order): Pensoft Publishers.

M3 - doi:10.3897/zookeys.393.6717

Wikipedia/ Citizendium:

<ref name="Liew2014ZooKeys393">{{Citation
| author = Liew T, Vermeulen J, Marzuki M, Schilthuizen M
| title = A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina
| journal = ZooKeys
| year = 2014
| volume = 393
| issue =
| pages = 1--107
| pmid =
| publisher = Pensoft Publishers
| doi = 10.3897/zookeys.393.6717
| url = http://www.pensoft.net/journals/zookeys/article/6717/abstract
| pmc =
| accessdate = 2019-07-21

}} Versioned wiki page: 2014-03-25, version 43788, https://species-id.net/w/index.php?title=Plectostoma&oldid=43788 , contributors (alphabetical order): Pensoft Publishers.</ref>

See also the citation download page at the journal.


Taxonavigation

Ordo: Architaenioglossa
Familia: Diplommatinidae

Name

Plectostoma Liew, Vermeulen, Marzuki & Schilthuizen, 2014Wikispecies linkPensoft Profile

Generic classification dispute

The genus Opisthostoma was described by Blanford and Blanford (1860)[2] based on one species–Opisthostoma nilgiricum from India. Adam (1865b)[3] described a second species of Opisthostoma, namely, Opisthostoma decrespignyi, which he previously described under the new genus Plectostoma (Adam 1865a[4]). Nevertheless, Blanford (1867)[5] concluded that the conchological differences between these two taxa were not enough to create a different genus. Instead, he suggested these could be two different subgenera. Next, another two subgenera–Gyrostropha Ancey, 1887 and Geothauma Crosse, 1892, were proposed for different forms of Opisthostoma and Plectostoma. However, Smith (1893a)[6] suggested that this subgeneric classification was not necessary until more data other than shell morphology were available. Since then, a classification into three subgenera within the genus Opisthostoma, namely, Geothauma, Opisthostoma, and Plectostoma has generally been accepted (e.g. von Martens and Thiele 1908[7], van Benthem Jutting 1932[8], van Benthem Jutting 1952[9]), until, in a recent review of the genus Opisthostoma, Vermeulen (1991[10], 1994[11]) followed a classification into only two subgenera, namely, Opisthostoma and Plectostoma.

Diagnosis

Despite the distinct ecological niche differences (see below–Distribution and habitat) between Opisthostoma and Plectostoma, it is not feasible to use this criterion in the genus identification, because information about the ecology is usually not available as most collections are made by soil sampling. After 150 years of work on Opisthostoma, it is still difficult to identify reliable apomorphic character states that can be used to distinguish between Opisthostoma and Plectostoma (Vermeulen 1991[10], 1994[11]). Both share the character state of the constriction, which is a slight shrinkage in the whorl towards the end of the spire. When the animal retracts into its shell, its operculum rests at the constriction (Vermeulen 1991[10]). It is, however, possible to make a morphological distinction between Opisthostoma and Plectostoma on the basic of the shell colouration in a fully grown adult, which is orange or pinkish in Plectostoma and white or pale yellowish in Opisthostoma. The colour differences between these two genera are very clear when comparing the living snails or freshly dead shell material (Figure 17, and Appendix 18). Some Plectostoma species have a regularly coiled tuba, and a shell form that is similar to Arinia. However, Plectostoma and Arinia can be easily distinguished by shell colour differences. The shell colour in Arinia is similar to that in Opisthostoma.

Description

Apex. Protoconch is either slightly, moderately or distinctly convex (Figure 3).
Spire. Height: 1.0 mm–3.7 mm. Width: 0.85 mm–2.60 mm (Figure 11). Number of whorls between 2 3/4–71/4. Apical spire shape: oblong or depressed conical (Figure 4). Basal spire shape: conical, ovoid or ellipsoid (Figure 5). Whorl periphery: flat, slightly, moderately or distinctly convex. Umbilicus: open, partially closed, or totally closed.
Constriction. Parietal teeth: parietal side of inner constriction whorl (Figure 2) with two long lamellae (Figure 6A), two ridges with a knob at each end (Figure 6B), one ridge with a knob at one end (Figure 6C), or no teeth (Figure 6D). Basal teeth: basal side of inner constriction whorl (Figure 2) with no teeth (Figure 7B), one ridge running parallel with the whorl growing direction, one ridge with a knob at one end running perpendicular to the whorl growing direction, or a combination of the latter two types (Figure 7A).
Tuba. Coiling direction: regular coiling (type 1, Figure 8A) or distorted (Type 2, or 3) (Figure 8B and C). Tuba whorl length in proportion to spire last whorl: ca. 3/8–1 1/2. Proportion of tuba that attaches to spire: whole to none.
Aperture and peristome. Peristome: simple aperture without outer peristome (Figure 10B), or double peristome (Figure 10C and 10D). Shape of outer peristome (Figure 10A): same as inner peristome and uniformly round, or highly projected or slightly projected at either a particular side or at a several sides of anterior, poteriorior, left and right laterial (Figure 9 and 10A).
Spiral lines. Either thick or thin, or only thin lines present (Figure 12).
Radial ribs. Rib density: 4–32 per mm on the spire’s last whorl in right lateral view (Figure 13A). Intensity: thick or thin (Figure 13B). Shape: straight, slightly curved, distinctly curved, single humped, single looped or double looped and the shape remaining the same or changing between between the spire and the tuba (Figure 13C, but single-looped, and double-humped not shown). Inclination: from orthoclin to prosoclin.

Distribution and habitat

The distribution range of Plectostoma is about 4.6 million square kilometres within the extent limited by 11°N, 97°E and 5°S, 120°E. However probably less than 5% of this large area is covered by limestone outcrops where suitable habitat may exist for obligate karst taxa like Plectostoma. The genus counts 79 species and occurs in Vietnam (1 species), Thailand (1), Peninsular Malaysia (28), Sumatra (1), and Borneo (48). Peninsular Malaysia, Sumatra and Borneo are part of the biogeographical region called Sundaland (Johnson 1964[12]). Plectostoma is found on most limestone hills. However, the genus is conspicuously absent on the limestone hills to the west of the central mountain ranges, such as the hills in the States of Perak and Kedah in Peninsular Malaysia, and in the northwestern half of Sumatra (Figure 18). No species have been recorded from the east coast of Sumatra, where hardly any limestone outcrops exist. Based on collection data and our field experience, there is a distinct ecological divergence between Plectostoma and Opisthostoma. This was already observed in the 19th century (Blanford and Blanford 1860[2], de Crespigny 1865[13], Blanford 1866[14]), and also by Berry (1961)[15]. Plectostoma can only be found in limestone outcrops, where the rock face is its major habitat, although a few individuals can occasionally be found on vegetation debris below the limestone rock face. Opisthostoma, on the other hand, is a soil dweller, living in leaf litter on the forest floor. They are mostly but not exclusively found in forest over limestone bedrock (Schilthuizen et al. 2003b[16]).

Phylogenetic relationships

Our molecular phylogenetic analysis reveals that Plectostoma, Opisthostoma, and Arinia are phylogenetically closely related (Figure 16). It is important to point out that the phylogenetic relationships among Plectostoma, Opisthostoma (except Opisthostoma vermiculum), Opisthostoma vermiculum, and Arinia are unresolved. Figure 16 shows representative shell morphologies of the taxa that were included in the phylogenetic analysis, and it is clear that it is rather difficult to find shared derived characteristics (synapomorphies) in size, spire shape, or tuba coiling regime, for either Opisthostoma or Plectostoma.
Nonetheless, we treat Plectostoma and Opisthostoma as two separate genera based on their ecological divergence and differences in adult shell colouration. Similarly, we propose that Opisthostoma vermiculum and Arinia should be considered as two separate genera. However, this hypothesis needs further testing with more genetic data from Opisthostoma vermiculum Clements & Vermeulen, 2008 (in Clements et al. 2008), the conchologically similar Opisthostoma gittenbergeri Vermeulen & Clements, 2008 and further Arinia species.

Taxon Treatment

  • Liew, T; Vermeulen, J; Marzuki, M; Schilthuizen, M; 2014: A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina ZooKeys, 393: 1-107. doi

Other References

  1. Crosse H (1892) Études malacologiques sur les genres nouveaux ou peu connus. Journal de Conchyliologie 32: 279–292. http://www.biodiversitylibrary.org/page/25234590#page/292/mode/1up
  2. 2.0 2.1 Blanford W, Blanford H (1860) Contributions to Indian Malacology. Journal of the Asiatic Society of Bengal 29: 117–127. http://www.biodiversitylibrary.org/item/124448#page/141/mode/1up
  3. Adam H (1865b) Descriptions of a new genus and some new species of mollusks. Proceedings of the Zoological Society of London 1865: 753–755. http://www.biodiversitylibrary.org/item/90954#page/543/mode/1up
  4. Adam H (1865a) Description of a new genus of land-shells from the Island of Labuan, Borneo. The Annals and Magazine of Natural History, including Zoology, Botany and Geology 3(15): 177. http://www.biodiversitylibrary.org/item/90412#page/859/mode/1up
  5. Blanford W (1867) On the Genus Plectostoma H. Adam, and the animal of Diplommatina Benson. The Annals and Magazine of Natural History, including Zoology, Botany and Geology 3(19): 305–307. http://www.biodiversitylibrary.org/item/72153#319
  6. Smith E (1893a) Note on the Genera Geothauma and Gyrostropha. The Annals and Magazine of Natural History, including Zoology, Botany and Geology 6(11): 284–285. http://www.biodiversitylibrary.org/page/24344618#page/332/mode/1up
  7. von Martens E, Thiele J (1908) Beschreibung einiger im östlichen Borneo von Martin Schmidt gesammelten Land und Süsswasser-Conchylien. Mitteilungen aus dem Zoologischen Museum in Berlin 4: 251–294. http://www.biodiversitylibrary.org/item/44411#page/272/mode/1up
  8. van Benthem Jutting W (1932) Notes on land Mollusca of the Malay Archipelago. Journal of Conchology 19(7): 196–210.
  9. van Benthem Jutting W (1952) The Malayan species of Opisthostoma (Gastropoda, Prosobranchia, Cyclophoridae), with a catalogue of all the species hitherto described. The Bulletin of the Raffles Museum 24(5): 5–61. http://rmbr.nus.edu.sg/rbz/biblio/24/24brm005-062.pdf
  10. 10.0 10.1 10.2 Vermeulen J (1991) Notes on the non-marine molluscs of the island of Borneo 2. The genus Opisthostoma (Gastropoda Prosobranchia: Diplommatinidae), part 1. Basteria 55: 139–163.
  11. 11.0 11.1 Vermeulen J (1994) Notes on the non-marine molluscs of the island of Borneo. 6. The genus Opisthostoma (Gastropoda Prosobranchia: Diplommatinidae), part 2. Basteria 58(3–4): 73–191.
  12. Johnson D (1964) A question of nomenclature. Malayan Nature Journal 18: 68–69.
  13. de Crespigny C (1865) Note on a shell from Labuan. The Natural History Review 5(20): 599. http://www.biodiversitylibrary.org/page/9749440#page/609/mode/1up
  14. Blanford W (1866) On Opisthostoma, H. Blanford, with description of a new species from the neighbourhood of Bombay, and of the animal and operculum. Proceedings of the Zoological Society of London 1866: 447–451. http://www.biodiversitylibrary.org/item/90954#page/545/mode/1up
  15. Berry A (1961) The habitats of some minute cyclophorids, hydrocenids and vertiginids on a Malayan limestone hill. The Bulletin of the National Museum 30: 101–105. http://rmbr.nus.edu.sg/rbz/biblio/30/30bnm101-105.pdf
  16. Schilthuizen M, Chai H, Kimsin T, Vermeulen J (2003b) Abundance and diversity of land-snails (Mollusca: Gastropoda) on limestone hills in Borneo. Raffles Bulletin of Zoology 51: 35–42. http://rmbr.nus.edu.sg/rbz/biblio/51/51rbz035-042.pdf

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