Research Article |
Corresponding author: Rodrigo Brincalepe Salvador ( salvador.rodrigo.b@gmail.com ) Academic editor: Frank Köhler
© 2020 Rodrigo Brincalepe Salvador, Daniel Caracanhas Cavallari.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Brincalepe Salvador R, Cavallari DC (2020) Taxonomy and distribution of enigmatic “helicoid” Polygyratia Gray, 1847 (Gastropoda, Stylommatophora). Zoosystematics and Evolution 96(1): 91-101. https://doi.org/10.3897/zse.96.51047
|
Herein, we present a taxonomic revision of the genus Polygyratia Gray, 1847, with a new systematic placement in Scolodontidae and containing only the species Polygyratia polygyrata (Born, 1778). We offer an updated morphological description and geographical distribution, based on museum specimens and occurrence data gathered from literature and online database iNaturalist. We synonymise P. charybdis Mörch, 1852 with P. polygyrata. The species is known only from Atlantic Forest areas in Bahia state, eastern Brazil. We exclude three other species from the genus Polygyratia, classifying them as: Systrophia (Systrophia) heligmoida (d’Orbigny, 1835) and S. (Entodina) reyrei (Souverbie, 1858), based on conchological features; and S. (E.) pollodonta (d’Orbigny, 1835), though tentatively, based on scant published data. Finally, we present the first report of S. (S.) heligmoida (d’Orbigny, 1835) from Brazil.
Atlantic Forest, Brazil, Eupulmonata, Helicoidea, iNaturalist, Polygyratia polygyrata (Born, 1778), Scolodontidae
Polygyratia polygyrata (Born, 1778) was one of the first terrestrial gastropods to be described from Brazil. After its original description, which did not provide a locality of origin, all subsequent major lists of terrestrial gastropods included the species, pinpointing its occurrence to the forests of Bahia (e.g.
Given that the knowledge about this species advanced very little since its description, we decided to reassess here all the information available regarding its taxonomy and geographical distribution, analysing museum specimens from worldwide collections, as well as online databases. We present here a formal re-description of the genus and its species, alongside venues for future research.
The main museum collections worldwide that could harbour specimens of Polygyratia were visited or contacted. Specimens were analysed for conchological characters (see below for molecular analysis) and the available locality data was compiled for a distribution map. Collection dates are unknown for most of the historical specimens, but at least a minimum age can be given to those that belonged to private collections by using the owner’s date of death (
The only specimens with soft parts that could be sampled for molecular studies (
Selected specimens were used for micro-computed tomography analysis (CT scan), scanned using a GE Phoenix v|tome|x s 240 industrial high-resolution CT & x-ray system at the Centro para Documentação da Biodiversidade (FFCLRP). This system is equipped with a DXR250RT 1,000 × 1,000 pixels detector; a diamond target was used with the following parameters: source operating at 60 kV, 100 μA, 1 × 1 binning, 333 ms exposure time, 1,200 projections, 1 frames skipped, 4 frames averaged, default offset and gain corrections. Image processing and 3D volume reconstruction were obtained using GE phoenix datos|x 2 and the subsequent volume analysis was carried out in VGSTUDIO 3.0 (Volume Graphics, Germany).
Abbreviations: Institutions:
Polygyratia
Gray, 1847: 173;
Ophiogyra
Albers, 1850: 91;
Helix Polygyrata Born, 1778, by monotypy.
P. polygyrata (Born, 1778).
Shell planispiral, multi-whorled and large for family. Body whorls marked by three angulations: one dorsal, one median and one basal. Aperture large (for family), rounded, with reflected peristome. Presence of short internal (not visible from aperture) parietal and palatal lamellae on body whorl. Aperture without barriers.
As P. polygyrata below.
The name Ophiogyra was introduced by
Helix Polygyrata
Born, 1778: 382;
Helix polygyrata: Born, 1780: 373, pl. 14, figs 19–20;
Helix polygyra [sic] Gmelin, 1788: 3624.
Helix Elongata Röding, 1798: 107.
Helix (Helicella) polygyrata: Moricand, 1836: 422.
Polygyra
? Polygyrata:
Polygyratia polygyrata:
Ophiogyra polygyrata:
Polygyratia charybdis Mörch, 1852: 7.
Polygyratia
(detrita.):
Helix charybdis:
Helix Charybdis:
Helix (Anchistoma) polygyrata:
Polygyra (Polygyratia) polygyrata:
Polygyra (Polygyratia) polygyrata var. charybdis:
Anchistoma polygyrata:
Polygyratia (Polygyratia) polygyrata:
Polygyratia (Polygyratia) charybdis:
Polygyratia polygyratia
[sic]
Polygyratia polygyrata polygyrata:
Polygyratia polygyrata charybdis:
Polygyratia charybdis:
Unknown (Born, 1780); “Brazil” according to
Reported (and maybe given) by
Eastern Bahia state, Brazil (Fig.
Museum specimens : Pará state (likely mistaken, see below). Bahia state: Baía de Todos-os-Santos (Todos-os-Santos Bay), Cachoeira (road to Una), Canavieiras, Ilhéus, Itabuna, Itacaré, Itaparica, Olivença, Pimenteira, Salvador, Serra Grande, Uruçuca, Una, Una Biological Reserve. Literature data: Cachoeira (Férussac, 1819, as “Caxoeira”). iNaturalist: Bahia state: São Sebastião do Passé. Internet: Bahia state: Ilhéus, Valença.
Atlantic Forest.
As for genus above.
Shell (Fig.
Shells of Polygyratia polygyrata, showing the variation in conchological characters such as size, number of whorls and aperture shape, as well as colouration. Scale bar = 2 cm. A. Holotype,
Internal lamellae in the shell of Polygyratia polygyrata. A. Broken specimen showing the second set of internal lamellae,
Brazil. Uncertain locality:
iNaturalist : BRAZIL. Bahia state: id 13527047 (São Sebastião do Passé municipality, lat -12.44740646 long -38.41546864, obs. Ben Phalan “deboas” 17/vi/2018 13:25:06 UTC); id 14349827 and id 14349831 (São Sebastião do Passé municipality, lat -12.45972252 long -38.40000153, obs. “sidnei-sampaio” 14/vii/2018 13:56:40 UTC). Other websites: BRAZIL. Bahia state: Allspira (Valença municipality, under dead leaves, 2006; http://allspira.com); Conchology (Ilhéus municipality, under dead leaves in tropical rain forest; https://www.conchology.be); Forum Francophone des Coquillages Actuels (Pimenteira municipality, under dead leaves in tropical forest, vi/2012; http://www.forumcoquillages.com/)
Even though
One of the localities of occurrence indicated by
The only locality indicated by a specimen outside Bahia state is Pará state, in northern Brazil (predominantly an Amazon Forest region), found on a specimen from a private shell collector (
Polygyratia charybdis was described by
The original description (
The possible holotype (Fig.
Polygyratia has always been classified in Helicoidea, albeit in diverse families, which mostly reflected the changing classification schemes of the Latin American helicoid lineages. Historically, it was classified in: Pleurodontidae (
The most recent works place the genus in Solaropsidae which, for a long time, was deemed a part of Helicoidea. It is now, however, considered to belong in Sagdoidea (
Despite our best efforts, we could not acquire specimens of Polygyratia suitable for molecular analysis. However, the unique shell morphology and conchological features are enough to sustain a revision of the historical classification and present a new family allocation for Polygyratia: the Scolodontidae.
Polygyratia, by conchological features alone (typically planispiral and multi-whorled shell; Fig.
Most Scolodontidae do not have teeth or lamellae, except for Entodina Ancey, 1887, which is often considered a synonym or subgenus of Systrophia (
There is scarce information in literature regarding internal lamellae in other scolodontids (e.g.
Curiously,
More certainty in the present classification of Polygyratia in Scolodontidae can only be achieved once fresh specimens are collected for molecular studies. Unfortunately, there is no information to be gleaned from the fossil record, as there are no known scolodontid fossils or “helicoid” forms similar to Polygyratia (
One meaningful implication of the proposed new classification is that scolodontids are generally supposed to be carnivores (but their biology remains largely unknown;
There is an interesting piece of information in literature (
We are very thankful to the following people for sending information and photographs about the specimens or for granting access to the collections under their care: Lily Berniker (
Internal shell structures of Polygyratia polygyrata (Born, 1778)
Data type: image
Explanation note: CT scan animation showing the internal lamellae in the shell of P. polygyrata (Born, 1778).