Why photo identifications remain tricky

With the increasing ease for using social media, a larger group of people become interested in putting a name to a shell. Some call this ‘citizen science’ as they think it is a means to involve the interested general public with e.g. taxonomic work. Others see it as a harmless pastime that nobody bothers. I think neither of the two is correct.

Internet can be a great help and for taxonomy it definitely is a great resource. Think alone of the Biodiversity Heritage Library (BHL), where a multitude of sources are becoming available and are made accessible for everyone. The means are there but does this mean that everybody can pick up a shell and compare it to literature found on the internet without good knowledge of the group concerned and the relevant area? I have strong doubts.

There are a lot of pictures of snails and shells on the internet with a proper locality. However, a specific locality alone does not qualify for a proper identification. Often characteristics of the species are concealed in the picture and different views are needed to know which species (singular or plural) might be concerned. Many times photos are good enough for making a correct guess of the genus concerned, but inadequate for a correct identification at the species level. Either because the photographer didn’t take the view(s) needed for a good comparison with figures in the literature, or the specimen wasn’t full-grown which prevents from showing the required characteristics needed for a correct identification.

My basic stand is field photographs are unsuitable for identifications, unless 1) full details are available on the locality and habitat, 2) proper care has been taken to photograph the shell (or snail) from such sides that all characteristics for identification are visible. Two caveat are immediately clear here: if the animal is still present it may obscure some of the characteristics needed for identification, and it may need a basic knowledge of the family concerned to know which views are needed to enable a specialist to put a name to a shell.
Thus the baseline is: photo identifications remain tricky, and personally I’m especially wary when it comes to lesser known species or species from lesser known areas.

This having said, today an example from Venezuela. It is taken from the blogpost of Ignacio Agudo-Patron who, if I’m correctly following the links, did not have the shell at hand himself but has put a name to pictures taken by one of his ‘Facebook friends’.


On first view this looks reassuring: a rather specific locality (“San Juan”, Dept. Sucre, Venezuela) and specific habitat information (premontane humid forest). There is even a reference to literature (my 2009 paper on the snail fauna of Venezuelan Guayana). Under the pictures in the blogpost is the identification “Plekocheilus (Eudolichotis) sp.”, which seems proper to me. However, the summary page of his post gives as identification “Plekocheilus (Eudolichotis) aff. gibber (Oberwimmer, 1931)”. While these pictures were taken in northern Venezuela at relatively low altitude, Oberwimmer’s taxon lives in southern Venezuela at more than 2000 m. It seems totally implausible to me that these pictures represent this species. Instead I think it is one of the coastal area species (P. (E.) distortus, and its allies) which are currently insufficiently known in their variation, distribution and relationships to allow a quick-and-dirty identification via photographs. After all, despite some scant literature, Venezuela is still one of the lesser-known areas in the Neotropics when it comes to snails.


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