Monthly Archives: May 2012

Photo of the day (134): Rabdotus

Stormy weather with lots of rain may awake lots of snails from dormancy. These pictures were taken in northwestern Florida, Santa Rosa County, Bagdad. Harry Lee recognized them as Rabdotus dealbatus (Say, 1821) and this is likely the first record for Florida of this species.

Thanks to Carole Tebay for sharing these pictures for identification.

Screen_shot_2012-05-30_at_09Img_0352Img_0353Img_0357Img_0360

Barrels and pagodas

Under this (beginning of the) title Piz?? & Cazzaniga (2012) published their fifth joint paper on Argentinian Plagiodontes species. 

Screen_shot_2012-05-25_at_18

As with the previous papers, this thoroughly deals with a few species and describes their systematic position, their anatomy and the distribution. The abstract reads as follows:
Plagiodontes weyenberghii (Doering, 1877) has a shell with a strong suprasutural keel; the species inhabits a restricted area in Central Argentina. Plagiodontes weyenberghii minor (Parodiz, 1939) was described as a subspecies with obese shells and broader geographic distribution; some populations were sympatric with Plagiodontes daedaleus (Deshayes, 1851). A discriminant analysis on 244 adult shells combined with original information on the internal anatomy confirmed the distinctiveness of P. weyenberghii weyenberghii, whereas P. weyenberghii minor showed a broad overlap with P. daedaleus and no evidence of anatomical differences. As a consequence, P. weyenberghii minor is considered a junior subjective synonym of P. daedaleus daedaleus (Deshayes, 1851). Plagiodontes weyenberghii (Doering, 1877) has unique characteristics such as the weak vascularization of the pallial system, the relative size of the penial papilla and its accessory lobe, the markedly swollen distal portion of the bursa copulatrix duct, the spermoviduct with two whorls, and the vagina with a medial depression.

Screen_shot_2012-05-25_at_20

Just another pearl in their suite of  revisionary papers on this genus.
Afbeelding_1_09-12-18
Reference:
Piz??, J. & Cazzaniga, N.J., 2012. Barrels and pagodas: clarifying the identity and variability of two nominal taxa of carinated land snaiuls in the genus Plagiodontes (Gastropoda: Orthalicidae: Odontostominae). – Journal of Natural History 46: 383-410.

New Thaumastus

A paper with a description of a new Thaumastus species from southern Brazil has just been published (Colley, 2012).

Screen_shot_2012-05-21_at_16

It describes a new species from Paran??, S??o Jos?? dos Pinhais e Guaratuba, Hydro-electric Powerplant Guaricana, Thaumastus straubei n.sp., for which also the anatomy (mandibula, radula and genitalia) is described. The holotype is in the Rio de Janeiro museum (MNRJ 11890).

Afbeelding_1_09-12-18
Reference:

Colley, E., 2012. Nova esp??cie de Thaumastus da Floresta Atl??ntica do Paran??, Brasil (Mollusca, Gastropoda, Pulmonata, Bulimuloidea). – Iheringia 102: 43-47.

Bothriembryon types

A new paper was just published (Breure & Whisson, 2012) on types of Bothriembryon snails from Australia. Not Neotropical, but from the Gondwanan part of the Orthalicoidea.

Besides the documentation of all extant type material, we have tried to make an overview of the type localities of the taxa and to include remarks on taxonomic problems which may be solved in future studies.

Screen_shot_2012-05-18_at_10

Also included are the fossil taxa for this group. Not many in absolute numbers (seven), but compared to the South American groups it is relatively good representation. The type of Bothriembryon gunnii (Sowerby, 1845), the only fossil taxon of which type material is kept outside Australia, is figured as a photograph for the first time.

0screen_shot_2012-05-18_at_10

Reference:
Breure, A.S.H. & Whisson, C.S., 2012. Annotated type catalogue of Bothriembryon (Mollusca, Gastropoda, Orthalicoidea) in Australian museums, with a compilation of types in other museums. ZooKeys 194: 41-80.

Quarternary terrestrial gastropods from Argentina

Some months ago, a big paper on the subject mentioned above was published by Miquel & Aguirre (2011). The abstract of the publication reads as follows:

This systematic review synthesizes our updated knowledge of 33 species and subspecies of Stylomatophoran gastropods, which belong to the genera Gastrocopta, Succinea, Radiodiscus, Retidiscus, Rotadiscus, Cecilioides, Austroborus, Megalobulimus, Bulimulus, Discoleus, Naesiotus, Plagiodontes, Spixia, Scolodonta, Miradiscops and Epiphragmophora . We provide published and unpublished records of the terrestrial molluscan taxa and a critical review, including data from the most important collections deposited in institutions from Argentina and abroad.
All the taxa described have modern representatives; only two, Succinea rosariensis and Scolodonta argentina, still require confirmation regarding their taxonomic validity. The genera with confirmed older than Quaternary records are Austroborus, Megalobulimus, Radiodiscus, Rotadiscus and Succinea,  which occur since the Paleogene.
Regarding the modern geographical distribution, well known records involve part of Argentina (Subtropical and Pampean Dominia of the Guayanian-Brazilian Subregion and the Central Dominion of the Andean Subregion, both in the Neotropical Region). The best-known fraction of the fossil molluscs recovered corresponds to species of medium to large-size dimensions, whereas taxa of less than 5 mm have very seldom been mentioned before. Approximately 60% of the species recorded belong to the Orthalicidae (=Bulimulidae), the Strophocheilidae represent ca. 15%, while other families like the Xanthonychidae, Charopidae and Scolodontidae provide ca. 10% each. This review made evident that the main contributions on this subject were published by Joaquín Frenguelli who was responsible for having formed and organize the most important Quaternary terrestrial collection from Argentina, made of over a hundred lots deposited at the Museo de La Plata (Invertebrate Palaeontology Department). The synthesis on the distribution and ecological requerimients of the taxa identified provide the basic source of reference necessary to carry out future palaeoenvironmental and palaeoclimatical interpretations, complementary of research work performed based on mammals, pollen and phytoliths, as well as to select significative and reliable taxa for geochronological and isotope analyses on shells from Neogene sediments traditionally known as chronostratigraphical units (Platense, Cordobense, Bonaerense, Ensenadense of the local literature).

This is an important paleontological contribution, since most of the known fossils of land snails are from Argentina, Brazil and Uruguay. The percentage of 60% for the contribution of the Orthalicidea (Orthalicoidea) agrees well with current number for some countries in the northern part of the continent (Breure & Mogollón 2010: fig. 1); it would be interesting to compare it with the percentage of modern Orthalicoidea in the Argentinan malacofauna.

Screen_shot_2012-05-09_at_20

Interesting was also to see the references with publication dates of Döring’s papers in the 1870s in Argentinan journals. In some cases they differ from the dates given by Neubert & Janssen (2004), which may have some importance since Döring published many new species. Thus datings may always be critical in case priority rules have to be applied. Unfortunately, the paper of Miquel & Aguirre doesn’t give any further details.
Afbeelding_1_09-12-18
References:
Breure, A.S.H. & Mogollón Avila, V., 2010. Well-known or little-known: miscellaneous notes on Peruvian Orthalicidae (Gastropoda, Stylommatophora). – Zoologische Mededelingen 84: 15-35.
Miquel, S.E. & Aguirre, M.L., 2011. Taxonomía de los gastrópodos terrestres del Cuartenario de Argentina. –  Revista Española de Paleontología 26: 101-133.
Neubert, E. & Janssen, R., 2004. Die Typen und Typoide des Natur-Museums Senckenberg, 84: Mollusca: Gastropoda: Pulmonata: Orthalicoidea: Bulimulidae (2), Orthalicidae, Placostylidae – Archiv für Molluskenkunde 133: 193-297.

Counting as science

Does counting count as science? Yes, it does in taxonomy. 

Apart from all sorts of morphological features which may be counted, sometimes the mere counting of specimens can be interesting. Especially when it involves the original type series.

In the Berlin museum I found several types of Placostylidae described by Bernhard Rensch from the Solomon Islands. This material became available to him through Eugen Paravicini, curator at the Anthropological Museum in Basel (now integrated in the current Naturhistorisches Museum Basel; NMB). During the 1920s Paravicini had made expeditions to the (then) British Solomon Islands where he also collected land mollusks.
In a letter of 21.i.1931 to Rensch, he asked for help with the identifications and offered to let him study the material.

Schermafbeelding_2012-05-03_om

In 1934, together with his wife Ilse, Rensch published a brief paper with diagnoses of several new species, some of which had been named after the collector, i.e. Paravicini (I. & B. Rensch, 1934). A more extensive paper based on the same material followed a year later (I. & B. Rensch, 1935). In the latter paper, Rensch had taken up the good habit of mentioning the number of shells with each description.

A few years ago, Andr?? Delsaerdt (2010) published his revision of the Placostylids from the Solomon Islands, and treated also the taxa described by Rensch. For each taxon the depository of the holotype was mentioned and the number of paratypes, which he had found in the NMB.

Bernhard Resch was curator of Malakozoologie at the Zoologisches Museum in Berlin (ZMB, now Museum f??r Naturkunde, Humboldt-Universit??t). Thus it was not surprising to find some “Typen” material in the ZMB collection of species described by him. All together material of 4 out of the 7 taxa described in his 1934/1935 papers were found with labels indicating “Paratypen”.

Schermafbeelding_2012-05-01_om

Putting my data together, I checked the number of specimens mentioned in Rensch’s papers and looked up his notes on the Basal material in Delseardt’s book. Two taxa need a special mentioning.

When describing Placostylus paravicianus Rensch mentioned “Es liegen 10 Schalen ??? vor”. In NMB, Delsaerdt found not only the holotype but also 10 paratypes; in the Berlin collection I found 2 paratypes. All together 13 specimens! Thus something has gone wrong, but where and how?
A similar problem occurs with Placostylus sanchristovalensis vicinus for which Rensch mentions in total 8 specimens. When I combine the data from Delseardt and myself, there are 10 specimens (including the holotype).
My tentative conclusion is that in these cases the number of paratypes has either been enlarged or someone has mis-counted the shells on his desk. 

Creative counting or just a stupid mistake? That’s the puzzling question that remains… 

References:
Delsaerdt, A., 2009 [2010]. Land shells on the Solomon Islands, I. Placostylidae. L’Informatore Piceno, Ancona, 132 pp.
Rensch, I. & Rensch, B., 1934. Diagnosen neuer Landschnecken von der Salomonen. – Sitzungsberichte der Gesellschaft Naturforschende Freunde zu Berlin (1933): 451-453 [published 29.v.1934]. 
Rensch, I. & Rensch, B., 1935. Systematische und tiergeografische Studien ??ber die Landschnecken der Salomonen auf Grund der Sammlungen von Dr. E. Paravicini und Dr. H. Hediger. Teil I. – Revue Suisse de Zoologie 42 (4): 51-86.

Land snails of Malpelo Island, Colombia

Just published, a paper on land snails of Malpelo Islands, Colombia (Hausdorf et al., 2012).

Schermafbeelding_2012-04-30_om

The fauna of the volcanic island Malpelo located west of Colombia’s Pacific coast includes only two species of land snails. One is a new endemic species of the subulinid genus Ischnocion, with which Rectobelus, Microbeliscus and Nannobeliscus are provisionally synonymized. Ischnocion conica new species differs from other species of the genus in the conical shell with radial palatal folds in juvenile stages. The other land snail species from Malpelo Island represents a new endemic thysanophorid genus. This genus, Malpelina (type species: Malpelina labiata new species), differs from other taxa of the Thysanophoridae in the yellowish-brown, depressed-globular shell with a distinctly thickened peristome, a broad glandular genital atrium, the lack of a vagina, a long penis, a long and exposed talon and the lack of entocones from all radular teeth. Malpelina is more closely related to Central American taxa than to thysanophorids from the Colombian mainland. Thus, it is more likely that Malpelo Island has been colonized by Malpelina from the north in accordance with palaeotectonic reconstructions. It is less clear whether Ischnocion reached Malpelo Island from Central or from South America, because the genus is distributed in both regions. Both species are patchily distributed on Malpelo and live under rocks in high densities. Their abundances increase towards higher altitudes. There is some segregation concerning the resting sites. Ischnocion conica rests on the soil or partially buried, while M. labiata almost always hangs from the underside of rocks. 

Reference:
Hausdorf, B., Kroll, O. & López-Victoria, M., 2012. The land snails of Malpelo Island, Colombia. – Journal of Molluscan Studies 78: 157-165.