Tag Archives: Leiostracus

Two new papers

Recently several new papers were published, of which two on Brazilian land snails are mentioned in this post.

This first is by Barbosa & dos Santos about morphological differences in a Happiella species at different localities in Ilha Grande.

Barbosa&dosSantos

The abstract reads: “We conducted a study on shell morphology variation among three populations of Happiella cf. insularis (Boëttger, 1889) inhabiting different areas (Jararaca, Caxadaço, and Parnaioca trails) at Vila Dois Rios, Ilha Grande, Angra dos Reis, state of Rio de Janeiro, Brazil. Linear and angular measurements, shell indices representing shell shape, and whorl counts were obtained from images drawn using a stereomicroscope coupled with a camera lucida. The statistical analysis based on ANOVA (followed by Bonferroni’s test), Pearson’s correlation matrix, and discriminant analysis enabled discrimination among the populations studied. The variable that most contributed to discriminate among groups was shell height. Mean shell height was greatest for specimens collected from Jararaca, probably reflecting the better conservation status of that area. Good conservation is associated with enhanced shell growth. Mean measurements were smallest for specimens from Parnaioca, the most disturbed area surveyed. Mean aperture height was smallest for specimens from Parnaioca, which may represent a strategy to prevent excessive water loss. Discriminant
analysis revealed that the snails from Jararaca differ the most from snails collected in the two other areas, reflecting the different conservation status of these areas: shells reach larger sizes in the localities where the humidity is higher. The similarities in shell morphology were greater between areas that are more similar environmentally (Caxadaço and Parnaioca), suggesting that conchological differences may correspond to adaptations to the environment”.

The second paper is by Salvador et al. correcting a lapsus in the neotype designation of Leiostracus subtuszonatus (Pilsbry, 1899). Now the illustration in Reeve’s Conchologica Iconica has been designated as lectotype.

Salvador et al f9

References:

Barbosa, A.B. & dos Santos, S.B., 2014. Morphology of the shell of Happiella cf. insularis (Gastropoda: Heterobranchia: Systrophiidae) from three forest areas on Ilha Grande, Southeast Brazil. – Zoologia 31: 230–238. Available at http://www.scielo.br/pdf/zool/v31n3/a04v31n3.pdf.

Salvador, B.R., Cavallari, D.C. & Breure, A.S.H., 2014. Corrigendum to “Taxonomic revison of Leiostracus onager and Leiostracus subtuszonatus (Gastropoda: Pulmonata: Orthalicidae)” by Salvador & Cavallari (2013). – Journal of Conchology 41: 627–628.

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A new Leiostracus

Recently a(nother) paper appeared of Salvador & Cavallari about a new Leiostracus species.

“A remarkable new species of pulmonate snail was recently collected in a small Atlantic Rainforest fragment near the city of Canavieiras, state of Bahia, Brazil, an area known for a high diversity of land snails. It is described herein as Leiostracus fetidus sp. nov. and can be easily identified by its color pattern of irregular brown to black axial stripes on a white to yellow background, a reddish axial band “separating” the white peristome from the rest of the shell and a broad brown spiral band surrounding the umbilical region. Other diagnostic features include a relatively small size, a proto columellar fold and two very weak folds delimiting the basal region of the aperture. This discovery is a reminder of how little this fauna is known and also an alarm for proper conservation of these forest fragments”.

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With the papers published so far (see also here) a comprehensive revision of the genus may be on its way or perhaps this is just the time-released version of it. Slowly and steadily. Thus we may look forward to the next bit…

Reference:
Salvador, R.B. & Cavallari, D.C., 2014. A new species of Leiostracus from Bahia, Brazil (Gastropoda, Pulmonata, Orthalicidae). – Iheringia 104: 39–42. Available at http://www.scielo.br/pdf/isz/v104n1/05.pdf

A new paper on Leiostracus

In the latest issue of Journal of Conchology a paper was published on two Leiostracus species. The authors, Rodrigo Salvador and Daniel Cavallari, summarize this as follows: Leiostracus subtuszonatus (Pilsbry, 1899) was originally described as a colour variant of L. onager (Beck, 1837). Here we conduct a taxonomic revision of these two species and regard them as separate taxa, distinguished by shell size, colour pattern, whorl convexity and protoconch sculpture. We also define a neotype for each species and offer updated descriptions, diagnosis and geographical ranges.

Here is a figure of L. onager as Salvador & Cavallari currently understand it:

And this how they see L. subtustozonatus:

It is always good to have a revision of species, especially if the authors are well-known with the fauna concerned as may be expected in this case. The paper thus definitely clarifies the status of both taxa if one follows the authors line of thought. However, there is a serious point of attention: for both taxa neotypes have been selected. The selection of neotypes is subject to rules of the IUCN (Art. 75). In Art. 75.3 the Code specifies seven conditions to be fulfilled:
</quote>
75.3.1. a statement that it is designated with the express purpose of clarifying the taxonomic status or the type locality of a nominal taxon;

75.3.2. a statement of the characters that the author regards as differentiating from other taxa the nominal species-group taxon for which the neotype is designated, or a bibliographic reference to such a statement;

75.3.3. data and description sufficient to ensure recognition of the specimen designated;

75.3.4. the author’s reasons for believing the name-bearing type specimen(s) (i.e. holotype, or lectotype, or all syntypes, or prior neotype) to be lost or destroyed, and the steps that had been taken to trace it or them;

75.3.5. evidence that the neotype is consistent with what is known of the former name-bearing type from the original description and from other sources; however, a neotype may be based on a different sex or life stage, if necessary or desirable to secure stability of nomenclature;

75.3.6. evidence that the neotype came as nearly as practicable from the original type locality [Art. 76.1] and, where relevant, from the same geological horizon or host species as the original name-bearing type (see also Article 76.3 and Recommendation 76A.1);

75.3.7. a statement that the neotype is, or immediately upon publication has become, the property of a recognized scientific or educational institution, cited by name, that maintains a research collection, with proper facilities for preserving name-bearing types, and that makes them accessible for study.

</unquote>

How are these conditions met in this paper?
One thing for sure, both neotype designations do not fulfil these provisions, specifically not Art. 75.3.4.
Although bending the rules, I think the selection of a neotype for Beck’s taxon is passable as there seems no type material for Bulimus zebra Spix, 1827—on which this taxon is based—to be present in the Munich museum where most of Spix’ types have been recognised. But it would have been better if the authors had shown that they had checked this with the responsible collection manager.
In the case of Pilsbry’s taxon—originally published as Drymaeus onager subtuszonatus in Pilsbry 1899: 95, pl. 14 fig. 17—this is obviously different. Although Pilsbry never selected type specimens for his taxa, it is known that Pilsbry’s type material is in the Philadelphia museum (ANSP). H.B. Baker sorted most of them out in the 1960s and published a list [Proc. ANSP 115: 191–259, subtuszonatus not mentioned]; Gary Rosenberg and his co-workers are now doing a great job to supplement this and digitise all data. A quick search in the ANSP database reveals three lots to be present, classified as “syntypes” for this taxon (ANSP 25960/4 specimens, ANSP 25963/1 specimen, ANSP 451837/3 specimens); only lot ANSP 25963 is mentioned by the authors. Thus there is ample material from which a lectotype could have been selected. And I remain puzzled why one lot of Pilsbry’s material has been mentioned in the paper, but is discarded without further discussion…

In my view, in this case, the ICZN Code is clear:
</quote>
75.8. Status of rediscovered former name-bearing types. If, after the designation of a neotype, the name-bearing type (holotype, syntypes, lectotype or previous neotype) of the nominal species-group taxon that was (were) presumed lost is (are) found still to exist, on publication of that discovery the rediscovered material again becomes the name-bearing type and the neotype is set aside (unless, following an application, the Commission rules that the neotype is to be retained as the name-bearing type).
</unquote>
Thus the designation of a neotype for Drymaeus onager subtuszonatus Pilsbry, 1899 is invalid given the extant type material in ANSP. An addendum to the paper could make this clear, and also correct the designation for Beck’s taxon to comply fully with the provisions of Art. 75 ICZN.

It is good that Salvador & Cavallari took the occasion to point out some corrections to the work of Simone related to these taxa. However, some of their other statements I cannot concur with; e.g., their sentence on p. 511 “L. subtuszonatus achieved the rank of a separate species from L. onager (Breure, 1979)” is a misinterpretation of my work. In that paper (p. 127) I have just listed the available names under the nominate genus Leiostracus, as the aim of the paper was a revision at genus level. Their remark (p. 516) that I gave “no formal definition or diagnosis” is besides the point. All taxonomic actions at species level had been separated in a previous paper (Breure, 1978 [Zool. Meded. 164]), where I didn’t mention this taxon.

Finally, given the colour variation seen within many arboreal species of this group, it may still be a good idea to have a detailed field study to verify the two morphs and their distribution. With so few shells collected from a relatively precise locality and lack of supporting anatomical data, more evidence would be welcomed.

 

Update

Pilsbry, when describing his taxon [Manual of Conchology (2) 12: 95, pl. 14 fig. 17], used as illustration a copy of a figure from Reeve [Conchologica Iconica 5, Bulimus: pl. 45 fig. 284]. The shell used by Reeve is in the London museum and also considered a syntype of Pilsbry’s taxon. The authors, having been informed of the above, said they will investigate this matter further.

Reference:
Salvador, R.B. & Cavallari, D.C. (2013). Taxonomic revision of Leiostracus onager and Leiostracus subtuszonatus (Gastropoda: Pulmonata: Orthalicidae). — Journal of Conchology 41: 511–518.