An unidentiable species of
?Radiodiscus Pilsbry, 1905
(Gastropoda; Charopidae) from the
Un poco del Chocó nature reserve
Una especie no identicable? de Radiodiscus Pilsbry,
1905 (Gastropoda; Charopidae) en la reserva natural Un
poco del Chocó
Marijn T. Roosen1*, & Nicole Büttner2
¹Natural History Museum of Rotterdam, Rotterdam, The Netherlands, https://orcid.org/0000-0001-
7651-6685
²Un poco del Chocó Reserve and Biological Station, Ecuador
Como citar este artículo:
Roosen M. Una especie no
identicable? de Radiodiscus
Pilsbry, 1905 (Gastropoda;
Charopidae) en la reserva natural
Un poco del Chocó. Revista
Ecuatoriana de Medicina
y Ciencias Biólogicas 45(1).
doi:10.26807/remcb.v45i1.970
Recibido: 28-10-2023
Aceptado: 01-04-2024
Publicado: 29-05-2024
*Corresponding author: marijn.roosen@gmail.com
DOI: https://doi.org/10.26807/remcb.v45i1.970
Resumen.- Se describe una concha rota de una especie de Radiodiscus de la reserva
natural Un poco del Chocó (provincia de Pichincha, Ecuador). Esta es la primera vez que
se describe e imagina una especie de Charopidae de Ecuador, pero como los taxones
pequeños no han recibido mucha atención en estudios anteriores se espera encontrar más
especies en el país.
Palabras clave: ?Radiodiscus, provincia de Pichincha, punto caliente Tumbes-Chocó-
Magdalena, Charopidae
Abstract.- A broken shell of a ?Radiodiscus species is described from the Un poco del
Chocó nature reserve (Pichincha province, Ecuador). This is the first time a species of
Charopidae from Ecuador is described and imaged, but as small taxa have not received a
lot of attention in previous studies more species are expected to be found in the country.
Keywords: ?Radiodiscus, Pichincha province, Tumbes-Chocó-Magdalena hotspot,
Charopidae
Introduction
Recently there has been a lot of attention for the continental gastropods in Ecuador, with
emphasis on providing a complete overview of all known species and the description of
obscure new taxa (Breure et al. 2022; Greke et al. 2023; Roosen 2023; Roosen & Dorado
2022, 2023; Roosen et al. 2023). However, all of these efforts are just a beginning and
many more taxa are found for the first time. Several of these species also belong to genera
and families hitherto not recognized in Ecuador or only reported as unknown genera and
species (e.g. Roosen 2019; Ramirez & Hausdorf 2022). Some families mentioned in Roosen
(2019), like the Charopidae, were already expected to be found in Ecuador by Correoso
(2008).
The purpose of this paper is to give a more elaborate description of the species of
Charopidae found in the Un poco del Chocó nature reserve, so far only reported in an
unpublished thesis by Roosen (2019), that is not widely available. Although the species
cannot be formally described, providing images and a detailed description might help
other scientists to recover more species.
Material & Methods
The shell of ?Radiodiscus sp. was collected from a leaf litter sample in the Un poco
del Chocó nature reserve, a small private reserve consisting of 15 hectares of lower
montane rainforest (secondary growth and primary forest). This sample was collected in
the secondary growth forest and searched without sieving, so the smallest species and
fragments could be collected. The shell was collected as part of a larger study, based on
which several new taxa were already described as new to science (Roosen 2023; Roosen
et al. 2023).
The collection methodology will be discussed more thoroughly in a forthcoming paper on
the ecology of all terrestrial gastropods collected from this reserve. Scanning Electron
Microscope (SEM) images were made with a variable pressure SEM at the Royal Belgian
Institute of Natural Sciences (RBINS).
Breure et al. (2022) and Correoso (2008) were used to establish whether it was an already
known Ecuadorian species. Aside from this, descriptions of similar Charopids were also
An unidentiable species of? Radiodiscus Pilsbry, 1905 (Gastropoda; Charopidae) from the Un poco del Chocó nature reserve
Vol. 45 Núm. 1: Mayo 2024
studied in an attempt to identify the species to the genus level (e.g. Pilsbry & Ferris 1905;
Hausdorf 2005). The specimen was deposited in the collection of the Instituto Nacional de
Biodiversidad (INABIO) in Quito, Ecuador. Other abbreviations used: m a.s.l. = meters above
sea level.
Systematic part
Charopidae F.W. Hutton, 1884
Radiodiscus Pilsbry, 1906
Remarks. Typical species of Radiodiscus have more, smaller spirals on the protonch.
Therefor we only tentatively assign this unknown species to Radiodiscus until more
material is available.
?Radiodiscus sp. 1
Studied material.- INABIOEC-MCL -1168 (one damaged shell, dry), Ecuador, Pichincha
Province, Un poco del Chocó nature reserve, near Las Tolas (Gualea), lower montane
rainforest, 1,200 m a.s.l., coordinates 00°03’10.8”N, 78°50’32.0”W, leg. M.T. Roosen 2019.
Description.- Shell small, subdiscoid, with a slightly raised spire and a deep suture.
Protoconch of ca. 1.5 whorls, sculptured with 7 strong spiral grooves between the shoulder
and the suture. Transition to teleoconch damaged. Teleoconch with 11 thin, distinct spirals
above the suture and numerous axial ribs of variable strength, ca. 60 on ½ whorl. The
spirals cross the axial ribs, creating a reticulate pattern on the shell. The cross section of
the youngest whorl is nearly circular, aperture and peristome broken. Umbilicus of medium
width (25-35 %), with axial ribbing on the umbilical walls (Figure 1).
Dimensions.- Diameter: 1.1 mm; Estimated maximum diameter: at least 2.0 mm; whorls: 3
½ (reconstruction).
Differential diagnosis.- It differs from other species of Radiodiscus in several aspects:
1) The spiralsculpture on the protoconch is stronger and not equally divided over the
protoconch whorl like in typical Radiodiscus; 2) Axial ribs on the teleoconch are usually
much stronger than the spiralsculpture, so the pattern of the shell would not be reticulate;
3) Axial ribs are usually more evenly distributed over the shell. No similar species are
known from Ecuador.
Distribution.- Ecuador: Pichincha Province: Un poco del Chocó nature reserve, near Las
Tolas (Gualea), lower montane rainforest, 1,200 m a.s.l.
Fig. 1. ?Radiodiscus sp., apical view. A: SEM image (photographed by Laetitia Despontin). B: USB microscope photograph (MR). Scalebar 100 um.
An unidentiable species of? Radiodiscus Pilsbry, 1905 (Gastropoda; Charopidae) from the Un poco del Chocó nature reserve
Vol. 45 Núm. 1: Mayo 2024
Remarks.- Based on the shell characters, the species discussed in this paper differs
significantly from all other known species of Radiodiscus. It might even be a representative
of a new genus, based on the protoconch sculpture. However, it is not possible to introduce
a new species (or genus) based on one damaged shell.
Discussion & Conclusion
The shell described in this paper is badly damaged. Although it is likely new to science
it cannot be named in this shape. However, all conchological characteristics that are
important to assign it to the Charopidae are still visible. This is important as this family was
so far only reported from Ecuador in the supplementary materials of Ramirez & Hausdorf
(2022).
The Charopid found in Un poco del Chocó fits within the general idea that many small
species of land snails have so far been overlooked in Ecuador. This is also reflected by the
many other new minute taxa reported from the Un poco del Chocó nature reserve (Roosen
2019; Roosen 2023; Roosen et al. 2023). We hope that brief contributions like this help
other scientists to recognize and describe these hidden gastropod species.
Acknowledgements
The current study was only possible because of the research permit (No. 007-2019-IC-
FAU-DPAPCH-MA), requested by the second author (NB). Mauricio Herrera Madrid (INABIO)
helped get the necessary permits to collect and deposit the specimen in the INABIO
collection. We would also like to thank Laetitia Despontin (RBINS) for photographing the
shell with the SEM.
Declaration of interest and Authors’ Contributions
All authors declare there is no conflict of interest. MR collected the material, arranged
the photography of the shell and wrote most of the species description. NB acquired the
necessary permits and contributed to the rest of the manuscript.
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