Monthly Archives: December 2018

Cerion from Bahamas

Another paper just published in the ‘end-of-the-year-stream’ is by Harasewych & Tenorio.

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Their abstract reads: “Morphometric analyses of shell shape of living specimens of Cerion inhabiting San Salvador Island segregate samples into two primary phenotypes, one inhabiting the western and southern coasts of the island, the other the eastern and much of the northern coast. These are concordant with phenotypes identified in prior morphometric studies. Lectotypes are designated for Cerion watlingense Dall, 1905; C. inconspicuum Dall, 1905; C. inconspicuum lacunorum Dall, 1905; and C. coloni Bartsch, 1924. The lectotype of Cerion watlingense Dall, 1905 falls within the western and southern phenotype, and is the oldest name available for this taxon. The lectotype of Cerion coloni Bartsch, 1924, a validly introduced, but previously unrecognized taxon, and the holotype of Cerion rodrigoi Gould, 1997 both fall within the group containing the east coast populations, with Cerion coloni Bartsch, 1924 being the oldest available name for this phenotype. A third, previously unrecognized phenotype, represented by a single inland population, is morphologically similar to the lectotype of Cerion inconspicuum Dall, 1905, which is the oldest available name for this phenotype. The geographical distribution and chronological succession of these phenotypes since the late Pleistocene is reviewed in the context of both the single and multiple colonization models for the arrival of Cerion on San Salvador, and the evolutionary and taxonomic corollaries of each model are discussed”.

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An interesting paper which shows that morphometric analysis may be needed when the morphology and distribution are seemingly entwined. The study of Cerion, which has intrigued many authors, has been elucidated with a thorough discussion of both the morphological and distributional aspects of the species of this island.

Reference:
Harasewych, M.G. & Tenorio, M.J., 2018. The genus Cerion (Gastropoda: Pulmonata: Cerionidae) on San Salvador [Watling Island], Bahamas: a geometric morphometric analysis of shell morphology. – The Nautilus, 132 (3-4): 71-82.

 

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New Subulinid from Brazil

Freshly pressed, a new genus and species from Brazil. Simone’s abstract reads “Lavajatus moroi is a new genus and species found in cave environment from Santa Quitéria region, Ceará, Brazil. It is mainly characterized by the very elongated shell measuring about 30 mm, the growth is uniform, adult shell of ~28 whorls, and the shell profile is rather straight. The species has an extraordinary capacity of retraction inside the shell, keeping empty from 1/3 to 1/2 of the shell length when retracted. Anatomically, lung lacking developed vessels; ureter entirely tubular; kidney wide, with narrow anterior projection; genital structures mostly located inside anterior half of the haemocoel; lack of jaw, esophagus very narrow; large pair of retractor muscles of buccal mass (m2), with a branch passing through the nerve ring; odontophore lacking horizontal muscle (m6), with cartilages ~3/5 fused with each other; spermoviduct having two regions, being the anterior one normally bearing young specimens; and nerve ring having a large visceral/ subesophageal ganglion. The dissection of the intrauterine young specimens, which normally have a swollen head and a posterior pedal flap, revels some interesting ontogenetic features, such as the extreme elongation of some structures, e.g., the lung and digestive tubes, the repositioning of some haemocoel structures, and the modification of the nerve ring (appearance of the pleural ganglia, fusion and migration towards anterior of the subesophageal ganglia) during the development. Comparison with known subulinines is performed, including accounts on the youth intrauterine development. The new species is almost troglobian, except for the presence of eyes”.

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As usual, there are many detailed drawings of the anatomy. The author has a specific, actual etymology for the genus name: “The generic name is a Latinization of the Portuguese words Lava Jato (car wash), an allusion to the Lava-Jato Operation, which designates a conjunct of investigations of Federal Police of Brazil, mostly investigating corruption crimes. The translucency of the shell, revealing the occult inner structures, is an afflatus”. Also the specific epithet is related to this: “The specific epithet is in honor to the judge Sérgio Fernando Moro, professor of criminal law in Federal University of Paraná, who is leading Lava-Jato Operation referred above. This is a demure acknowledge of his effort in remodeling Brazil into a better country”.

Sometimes scientists try to make pinholes in the actual world; this is how far a taxonomist can go….

Reference:
Simone, L.R.L., 2018. Lavajatus moroi, new cavernicolous Subulininae from Ceará, Brazil (Gastropoda, Eupulmonata, Brazil). – Spixiana, 41 (2): 173-187.

 

Fossil gastropods from Uruguay

Cabrera et al. published a paper on Late Cretaceous molluscs from Uruguay. Their abstract reads: “Paleoecological studies of continental gastropods give valuable information about the depositional environment of the fossil assemblages. In South America, these assemblages from the Late Cretaceous/ Paleocene are scarce and poorly studied. Most works focuses on taxonomy, but a paleoecological approach is still missing. We analyzed the assemblages present in the Queguay limestones from Uruguay. The total fossil content consists in freshwater and terrestrial gastropods, characean gyrogonites, ostracods, Neosauropoda eggshells, vegetable remains, insect nests, and pupal chambers. As the precise age and sedimentary environment of the Queguay limestones have been discussed for almost nine decades, a paleoecological study was conducted in order to answer these questions from this point of view. Diversity (Simpson, Shannon-Wiener, equitability) and similarity (Jaccard and Kulczynski) indices were calculated; the analyses showed a close relationship among all locations, and therefore we conclude that there are not differences in fossil content among the localities. Moreover, the data allows to consider them basically of the same environment and age. The presence of Neosauropoda eggshells in several outcrops indicate unquestionably a Late Cretaceous age, and establish the oldest record worldwide for Pupillidae, Orthalicoidea and Biomphalaria”.

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The fact that the fossils mentioned establish the oldest known facies for several genera (Pupoides, Bulimulus, Bahiensis, and Biomphalaria) is an important result of this study. This might be useful data for future use when one needs fossil species for calibrating  phylogenetic data.

Reference:
Cabrera, F. et al., 2018. Continental Late Cretaceous gastropod assemblages from Uruguay. Paleoecology, age, and the oldest record for two families and a genus. – Historical Biology, advance online. DOI: 10.1080/08912963.2018.1471478.

New Carychium from Panama

A recent paper by Jochum et al. described a new species of the micro-mollusc genus Carychium using modern CT-scanning.

The abstract reads: “Five years ago, the Panamanian evolutionary lineage (EL) C12 was uncovered along with four other ELs in an integrative phylogenetic investigation of worldwide Carychiidae. Since EL C12 lacked shell material post-molecular analysis to serve as a museum voucher, it remained undescribed. Now, after recent collection efforts of C12 and the congener, Carychium zarzaae Jochum & Weigand, 2017 at their original Panamanian sites, C12 is morphologically described and formally assigned the name, Carychium panamaense Jochum, sp. n. In sync with recent taxonomic treatment of the genus, computed tomography (CT) is used in this work to differentiate shells of C. panamaense sp. n. from geographically-proximal, Caribbean, North and Central American congeners. Recent material of topotypic Carychium jardineanum (Chitty, 1853) and undamaged C. zarzaae were additionally CT-scanned and assessed in the comparative analyses”.

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CT-scanning is a promising technique, especially for molluscs with internal folds or dents, and for micro-molluscs. Also anatomical details may be imaged and reconstructed in this way, as was previously shown in this proof of principle.

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Reference:
Jochem, A. et al., 2018. Fulfilling the taxonomic consequence after DNA Barcoding: Carychium panamaense sp. n. (Eupulmonata, Ellobioidea, Carychiidae) from Panama is described using computed tomographic (CT) imaging. – ZooKeys, 795: 1-12.

Clessinia from Argentina

A recent paper by Cuezzo et al. provides a revision of Argentinian species. Their abstract reads in full:

“Background: Land gastropods of the Dry Chaco merit special attention because they comprise a highly diverse but barely studied group. Clessinia Doering, 1875 are typical inhabitants of this ecoregion. The inclusion of their distribution areas into Spixia range, their shell shape similarities, and a former molecular study raised doubts on the monophyly of this genus. The present study review the species of Clessinia, under a morphological, geometric morphometrics, and molecular combined approach.
Methods: Adults were collected, photographed, measured, and dissected for anatomical studies. Shell ultrastructure was studied with scanning electron microscope. Geometric morphometric analyses on shells were performed testing if they gave complementary information to anatomy. Two mitochondrial genes, and a nuclear region were studied. Phylogenetic reconstructions to explore the relationships of DNA sequences here obtained to those of Clessinia and Spixia species from GenBank were performed.
Results: Species description on shell, periostracal ornamentation and anatomy is provided. We raised former Clessinia cordovana striata to species rank, naming it as Clessinia tulumbensis sp. nov. The periostracum, consisting of hairs and lamellae, has taxonomic importance for species identification. Shell morphometric analyses, inner sculpture of penis and proportion of the epiphallus and penis, were useful tools to species identification. Nuclear markers do not exhibit enough genetic variation to determine species relationships. Based on the mitochondrial markers, genetic distances among Clessinia species were greater than 10%, and while C. cordovana, C. nattkemperi, and C. pagoda were recognized as distinct evolutionary genetic species, the distinction between C. stelzneri and C. tulumbensis sp. nov. was not evident. Clessinia and Spixia were paraphyletic in the molecular phylogenetic analyses. Species of Clessinia here treated have narrow distributional areas and are endemic to the Chaco Serrano subecoregion, restricted to small patches within the Dry Chaco. Clessinia and Spixia are synonymous, and the valid name of the taxon should be Clessinia Doering, 1875 which has priority over Spixia Pilsbry & Vanatta, 1894.
Discussion: Our results support the composition of C. cordovana complex by three species, C. cordovana, C. stelzneri, and C. tulumbensis sp. nov. The low genetic divergence between C. stelzneri and C. tulumbensis sp. nov. suggests that they have evolved relatively recently. The former Spixia and Clessinia are externally distinguished because Clessinia has a detached aperture from the body whorl forming a cornet, periostracal microsculpture extended over dorsal portion of the peristome, five inner teeth on the shell aperture instead of three–four found in Spixia. Morphological similarities exists between both genera in shell shape, type of periostracum microsculpture, reproductive anatomy, besides the overlap in geographic ranges”.

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This is an interesting paper for me, as more than 6 years ago I did research on type material in the London museum and found the species of the two ‘genera’ difficult to entangle, the more when phylogenetic results proved a paraphyletic relationship (Breure & Romero, 2012). This study comes to the same phylogenetic outcome as shown in the figure below. And for clarity: the Clessinia specimens used in our 2012 study were identified and supplied to us by one of the current authors and another Argentinian malacologist; they had more expertise and resources available.

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The conclusion of the study by Cuezzo et al. is that Clessinia and Spixia are synonyms, with the older name (Clessinia) taking precedence. As such this is correct, but at the same time they conclude that the two ‘genera’ are morphological distinguishable (see the Discussion in their abstract). As taxonomists we have a solution for this: the subgenus…, which is treated in MolluscaBase as ‘alternate representation’. So instead of complete synonymisation, I would say there seems enough reason to distinguish the two as subgenera despite not being strictly monophyletic. The nomenclature then becomes:

Clessinia Doering, 1875
Clessinia (Clessinia) Doering, 1875 – type species Bulimus (Clessinia) stelzneri Doering, 1875.
Clessinia (Spixia) Pilsbry & Vanatta, 1898 – type species Clausilia striata Spix in Wagner, 1827.
See Cowie et al. (2004) for details on the names of Spix and Wagner.

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In this paper also one new species is described. The authors say “The new species, Clessinia tulumbensis sp. nov. include Clessinia cordovana striata (Parodiz, 1939). The name striata has not been used here to avoid homonymy with Pupa striata Spix, 1827 [= Clausilia striata Spix in Wagner, 1827], the type species of Spixia, since in the present study the genera Clessinia and Spixia are proposed as synonymous. The new species with its own holotype and paratypes is defined based on live-collected material from which DNA sequences were obtained and the anatomy described. In this sense, although the Parodiz name is preoccupied, we are not replacing the name proposed by him in 1939 but creating a new species with its own type series”.

With Parodiz’ name mentioned by the authors as a full synonym, I fail to see the reason to introduce the name tulumbensis as a species novum. Although it is correct to replace the name of Parodiz to avoid homonymy, it is nonsense to say that you can introduce a replacement name with its own type series. The name tulumbensis is thus not a ‘sp.nov.’ but a nomen novum. And the holotype of Clessinia cordovana striata Parodiz, 1939 (MACN-In 9127) becomes automatically the holotype of Clessinia tulumbensis! The “holotype IBN 883” and the paratype material mentioned in this paper has no status other than being vouchers for this study.

References:
Breure, A.S.H. & Romero, P.D., 2012. Support and surprises: a new molecular phylogeny of the land snail superfamily Orthalicoidea (Gastropoda, Stylommatophora) using a multi-locus gene analysis. – Archiv für Molluskenkunde, 141: 1–20.
Cowie, R.H. et al., 2004. The South American Mollusca of Johann Baptist Ritter von Spix and their publication by Johann Andreas Wagner. – The Nautilus, 118: 71-87.
Cuezzo, M.G. et al., 2018. From morphology to molecules: a combined source approach to untangle the taxonomy of Clessinia (Gastropoda, Odontostomidae), endemic land snails from the Dry Chaco ecoregion. – PeerJ, 6: e5986 (54 pp.).

Checklist of Pulmonate fossils

Just published by a group of 6 authors, Salvador et al. have made an annotated checklist of known Pulmonate gastropod fossils. In their own words “The South American fossil record of pulmonate gastropods counts with circa 100 species from the Cretaceous to the Pliocene. As this knowledge is largely scattered in the literature, we present here a checklist of these fossils, with relevant data about each species’ type locality, stratum and age, and illustrating the type specimens whenever possible. Moreover, some taxonomical problems are highlighted in the hope of garnering attention for future research”.

Fossils from the following families are treated: Chilinidae, Lymnaeidae, Planorbidae, Physidae, Achatinidae, Ferussaciidae, Charopidae, Punctidae, Cerionidae, Urocoptidae, Succineidae, Strophocheilidae, Bulimulidae, [Megaspiridae], Odontostomidae, Orthalicidae, Simpulopsidae, Gastrocoptidae, Pupillidae, Clausiliidae, and Xanthonychidae.

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A checklist like this is always a helpful instrument to bring knowledge together in one point, to highlight gaps and to make suggestions for future research.

Reference:
Salvador, R.B. et al., 2018. Annotated catalogue of the fossil Hygrophila and Eupulmonata (Mollusca: Gastropoda) from South America (Cretaceous – Neogene). – Neues Jahrbuch fuer Geologie und Palaeontologie Abhandlungen, 289 (3):249-280.