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.


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”.


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… 

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.

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