Monthly Archives: March 2019

Photo of the day (179): Cerion

Today a picture of Cerion uva as ‘found footage’ in a mail from the Speurneuzen group. The photo was made during an excursion along Rooi Katoen at Curacao.

21 Wat Gerlof fotografeerde (4)


More on Humboltiana

Another paper on Humboldtiana appeared as an advance online paper; it is by López, Zúñiga & Mejía. Their abstract is “It has been postulated that Pleistocene climatic change has promoted repeated contraction and expansion of the distributions of montane taxa in Mexico (‘see-saw effect’). Under such a scenario, we would expect taxa, particularly those with limited dispersal such as land snails, to exhibit strong phylogeographic struc- ture. Using an approach based on four molecular markers (COI, 16S, ITS1 and ITS2), we investigated the phylogeography of Humboldtiana durangoensis, a land snail endemic to the Madrean central region of the Sierra Madre Occidental of Western Mexico. We sampled a total of 178 individuals from 16 localities spanning the known geographic range of the taxon. Two main groups of H. durangoensis were recovered, one occupying the northern part of the current range of the species and the other the southern part. While these two groups show high haplotypic diversity and low nucleotidic diversity, suggesting a recent demographic expansion, our Bayesian Skyline Plots point to a more complex demographic history, involving expansion and contraction of the effective population size. The phylogeographic structure of H. durangoensis in the Sierra Madre Occidental may possibly be a result of Pleistocene climatic changes”.

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As postulated before in literature, land snails are good model organisms for this kind of phylogeographical studies. It is noteworthy that this group of Mexican researchers have begun to study this group of land snails as shown by this recent post.

López, B. et al., 2019. Phylogeographic structure in the apparent absence of barriers: a case study of the Mexican land snail Humboldtiana durangoensis (Pulmonata: Humboldtianidae). – Journal of Molluscan Studies : (9 pp.) [advance online] doi:10.1093/mollus/eyz007

Roeters van Lennep (1820-1879)

Freshly pressed: a new paper on the history of malacology, i.e. about the 19th Century Dutch cabinet collector H.C. Roeters van Lennep.

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H.C. Roeters van Lennep was one of the most famous Dutch shell collectors during the mid-19th century, for whom we here present new and additional biographical information. His collection was auctioned in 1876, but so far only a limited amount of information has been published on this topic. The details of the auction are reconstructed on the basis of his correspondence with H. Crosse. Such new information provides an insight into who buyers were during the auction, which prices were realised, and where parts of the material ended up. There ap- pears to have been a second auction in 1879 where possibly a large part of the remainder of the first auction was sold.

Breure, A.S.H. & Backhuys, W. Herman Christiaan Roeters van Lennep (1820-1879) and the auction of his collection. – Spirula, 418: 10-16.

Belize land snails

A new book by Dourson et al. on the non-marine malacofauna of Belize is a peculiar case, which shows that privately publishing a book including new taxa might be a tricky case.

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The non-marine malacofauna of Mexico and Central America is seemingly well-known through the work of the late Fred G. Thompson. His checklist, of which the final version appeared in 2011, listed all the currently accepted (sub)species and synonyms known from that area. It was a major milestone after the previous works by Crosse & Fischer’s Mission au Mexique et Guatemala, …Mollusques (1870-1902) and Von Martens’ molluscan part of the Biologia Centrali-Americana (1890-1901). Thompson’s publication, listing ca. 1250 taxa for this enormous area, stated that this number possibly only reflects one third of the actual malacofauna, due to the fact that most countries have only partially been surveyed for molluscs. 

Dourson et al. have concentrated on Belize, a relatively small country which borders southern Mexico and Guatemala. During the period 2006-2016 they surveyed all the seven physiographic regions of the country. And where Thompson only listed 24 species they enumerate 158 in total, of which 17 newly described in this book, with three others recently described in journals and a further eight still not formally described. This constitutes an increase of 658% for the biodiversity of non-marine snails in this country!

The authors have set up this book in such a way that it is aimed for a broad public, both scientists and laymen. After the introductory chapter, two chapters are dealing with general information on land snails and the value of snails in ecosystems respectively. The next chapter ‘Collecting and Identifying Land Snails’ also explains the organisation of the book. Chapters 5-12 treat land snails according to their shape and size, followed by a chapter on slugs and one on freshwater snails. The final chapter is dealing with exotic snails occurring in Belize. The book is concluded by a glossary, a species list per family, a bibliography, and an index of scientific names.

The first version of this book (Dourson et al., 2018a) was unintentionally published while the authors were still updating the text on the basis of reviews they had asked to specialists. Nevertheless, the book was distributed by several commercial companies, and the new species descriptions are thus validly available according to the International Code on Zoological Nomenclature. This date was 10 January 2018; the final, ‘official’ version came out just before Christmas on 21 December (Dourson et al., 2018b). 

The ‘unofficial’ first version was based on old classifications for several families (e.g., Orthalicidae contained both Orthalicus [Orthalicidae] and Bulimulus and Drymaeus [Bulimulidae]; no distinction was being made between Urocoptidae and Epirobiidae; Subulinidae were not included in Achatinidae). The classification of Ampullariidae is not in accordance with the authoritative papers of Cowie. In June 2018, after receiving a further draft of the book, I send a long list with additional comments to the authors. Thus it is regrettable that this version was published at all. Unfortunately part of the suggested corrections were not applied (e.g., p. 11: Morlet’s crocodile should be Morelet’s crocodile; p. 26: the ‘escargot’ of the French is not Cornu aspersum but Helix pomatia; p. 227: the correct name for the species is Brachypodella speluncae (L. Pfeiffer, 1852), and the syntype figured on p. 226 is Cylindrella costulata Morelet, 1851 [Pfeiffer’s name being a replacement name for this junior homonym]). Some figures have been updated and the list of references is somewhat extended but still contains typos and flaws, while recent literature on several groups are missing.

The following new species have been described (publication date thus January 2018), with the holotypes deposited in the Florida Museum of Natural History, Gainesville:

Family Helicinidae: Lucidella caldwelli
(Note that since authorship has not been restricted, Caldwell is co-author of his own eponym)

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Family Bulimulidae: Drymaeus tzubi
(N.B. in this version incorrectly classified as belonging to Orthalicidae)

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Family Spiraxidae: Euglandina fosteri

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Family Spiraxidae: Pseudosubulina juancho

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Family Spiraxidae: Rectaxis breweri

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Family Achatinidae: Opeas marlini
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Leptopeas corwinii
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Lamellaxis matola
(N.B. in this version still under the family Subulinidae)

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Family Achatinidae: Leptinaria doddi
(N.B. in this version still under the family Subulinidae)

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Family Urocoptidae: Brachypodella levisa

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Family Thysanophoridae: Thysanophora meermani

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Family Scolodontidae: Miradiscops striatae

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Family Scolodontidae: Miradiscops youngii

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Family Scolodontidae: Miradiscops bladensis

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Family Charopidae: Rotadiscus saqui

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Family Charopidae: Chanomphalus angelae

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Family Ferussaciidae: Cecilioides dicaprio

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This book is an extremely nice contribution to our knowledge of the Central American malacofauna. It is suitable both for both the ‘serious’ malacologist and for a layman, thanks to the very accessible way the book was designed. But, as the authors communicated to me, the prime audience is the general public. The lay-out will appeal to this target group, although the silly cartoons could be missed without making the book less informative.

As far as I know, the authors are now giving workshops to people in Belize to bring this fauna more to their attention. They will also develop a laminated snail card for quick identifications in the field. All this sounds as wonderful initiatives.

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Update: The final version of the book came meanwhile available, and this post has been updated. It is unfortunate that the authors have not grasped the opportunity to correct some of the errors in Thompson’s checklist and that the classification is not up-to-date. It is clear that the first, unofficial version will become a collector’s item for bibliophiles!

Dourson, D.C., Caldwell, R.S. & Dourson, J.A., 2018a. Land snails of Belize, Central America. A chronicle of remarkable diversity and function. — Goatslug Publications, Stanton, Kentucky, U.S.A. Hardcover, 338 pp. ISBN 978 0999 802304. [no longer available]

Dourson, D.C., Caldwell, R.S. & Dourson, J.A., 2018b. Land snails of Belize, Central America. A chronicle of remarkable diversity and function. — Goatslug Publications, Stanton, Kentucky, U.S.A. Softcover, 339 pp. ISBN 978 0999 802311. € 69. 

New Tryonia from Brazil

Almeida Guimaraes et al. have studied a sample of fossil freshwater gastropods from northwestern Brazil. Their abstract “This paper deals with the record of gastropods of the family Cochliopidae, genus Tryonia, from the Mio-Pliocene Solimões Formation, from the borehole 1AS-34-AM drilled in the upper Jutaí River, Amazonas State, Brazil. We report four species, including Tryonia scalarioides scalarioides, Tryonia cf. T. nuttalli, besides of a new species and other kept in open nomenclature”.

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The new species described is Tryonia globosa and the holotype is in the Paleontological Section of the Museu Paraense Emílio Goeldi (MPEG 2357-I/1).

de Almeida Guimaraes, L.I. et al., 2018. New records of Tryonia (Gastropoda, Cochliopidae) from the Mio-Pliocene Solimoes Formation (State of Amazonas), Brazil. – Revista Brasileira de Paleontologia, 21 (3):255-264

Fossils from NE Mexico

Vega et al. just published a paper on fossils from northeastern Mexico. Their abstract reads as follows: “Additions are offered to the diverse estuarine, freshwater and terrestrial gastropod fauna of the Upper Cretaceous (Campanian) and Paleocene lithostratigraphic units of the Difunta Group, NE México (Coahuila and Nuevo León). Nineteen species of continental gastropods (five of them new) are reported and illustrated from the upper Campanian Cerro del Pueblo Formation (Las Águilas/Porvenir de Jalpa locality) and the Paleocene Las Encinas Formation (La Leona locality), northern Parras Basin, Difunta Group, Coahuila. The first record of pulmonate gastropods from the Difunta Group is based on several specimens of different species. This is the third contribution dealing with these continental gastropods from the study region and a revised list of reported species is presented. Although we follow the most recent classification of continental gastropods, we also base the identification on paleonto- logical systematics, knowing that some important diagnostic features were not preserved. Thus, we do not intend to propose paleobiogeographic or evolutionary inferences. Our main goal is to present the paleodiversity known from the study area, in hope that these data would be useful for more detailed studies in the near future”.

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The new species are Goniobasis unilirata, Pleurocera gigantica, Birgella burchi, Haitia taylori, and Holospira thompsoni. All new taxa are authored by Naranjo-García & Aguillón.

Vega, F.J. et al., 2019. Additions to continental gastropods from the Upper Cretaceous and  Paleocene of NE Mexico. – Boletin de la Sociedad Geologica Mexicana, 71 (1):169-191.

Poecilozonites from Bermuda

Just published, a study by Hearty & Olson about fossils of Poecilozonites from Bermuda. Their abstract reads: “Considerable refinement of the surficial geology and biostratigraphy Bermuda has resulted in the proper ordering of the phylogenetic sequence of Poecilozonites, and thus offers an opportunity to examine evolutionary pathways within this taxon. Paedomorphism, the retention of juvenile ontogenetic characteristics into adulthood, is a recurrent morphological manifestation in fossil land snail shells of the subgenus P. (Poecilozonites) on this isolated oceanic island. The paleontology of this endemic taxon has been examined over the past century and was a key example of‘‘punctuated equilibria’’ (PE) in the late 1960s and early 1970s. In a previous study, we documented the biostratigraphy and geochronology from the known fossil record of P. (Poecilozonites) representing at least the past 500 kyr. Here we focus specifically on paedomorphic forms that appeared in shells at the onset of the last interglaciation, marine isotopes stages (MIS) 6/5e and again at the beginning of the Holocene (MIS 2/1). There are many possible mechanisms to explain the occurrence of paedomorphism including PE, but of importance to this discussion is that neither the size nor the fossil record of Poecilozonites show three independent lineages as proposed by Gould (1969). Gould’s several named paedomorphic forms supposedly branching from P. bermudensis over the past 300 kyr, occur only during the last interglacial (sensu lato) MIS 5, and the Holocene (MIS 1). Both punctuation and stasis characterize the morphological changes of this taxon over the past 140 ka, but these changes are reversible, and no speciation is evident”.

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With a lot of evidence these authors have solved this seemingly complex sequence of different forms, and reduced it to a single species. This species is still extant (see previous post).

Hearty, P.J. & Olson, S.L., 2019. Environmental stress and iterative paedomorphism in shells of Poecilozonites (Gastropoda: Gastrodontidae) from Bermuda. – Palaios, 34 (1): 32-42.