Identification area Hi all, does someone here on the forum know the difference between Caracolus marginellus (= Pleurodonte marginella) and Caracolus sagemon? Is there anything new about this topic? I'm looking for papers dealing with this question, because several authors (including Pilsbry) have intensively dealt with this question and regard sagemon as a synonym of marginellus. Of course there are a lot of different subspecies (?), at least forms in the marginellus-complex (such as "rostratus/a", "semiapertus/a" and so on), but these surely do not represent different species. Thanks for any kind of help, I wish you a nice weekend (not a weak end....... ): wolf
I'm way out of my comfort zone here as these are not West African species. But may I hazard a guess Wolf ? Habitat ! Caracolus marginellus is from Puerto Rica. Caracolus sagemon is from Cuba. Would this make any sense ? Of course one would have to know whats going on for the island of Haiti/Dominican that lies in the middle of these 2 island groups.
Hi brunni, thanks a lot for your answer. Nice to read you again…… . Yes, I’m back in this forum…….. .
Japs, perhaps the habitat is important. Unfortunately it’s a rather complicated story. In 1791, Gmelin took two (!) different pictures to define his Caracolus marginellus. Crazy enough, in 1837 Beck took one of these pictures to define his Caracolus sagemon. Crazy again, as far as I know, Beck gave no description of his sagemon. Later on, Pilsbry compared hundreds of specimens from allover the Caribbean and he saw no need to define two species at all (see Manual of Conchology). Following his opinion, there’s only a rather variable species called Caracolus marginellus (= Pleurodonte marginella) with several forms and sagemon is a synonym. But if we accept two species, what are the conchological differences and how about the morphological differences concerning the genital apparatus? Are there any molecular genetic studies? Some specimens are sold as Caracolus marginellus, others as Caracolus sagemon. Is the only reason for this differentiation just the habitat, the origin of the specimens or are there valid conchological and/or morphological reasons for using two names? Sorry, going into details causes trouble, sometimes……. .
We are all pleased to see you back here Wolf. If 1791, Gmelin's pictures were of two different specimens ( i.e not of same shell from different view point ) he could have inadvertently described 2 similar species under one name. In general there is a good case to be made for differentiating insular populations that are unable to interbreed. I am not conversant with publications on the Carribean species but as you know all early authors ( as well most current ones ! ) totally ignore soft tissue when describing new species based on shell description alone. I will send you a PM with the details of an American who has collected landsnails extensively in the Caribbean and would imagine he is up-to-date on publications for species from this area. Hope this might help !
Hi brunni, many thanks for all! Yes, no one knows whether Gmelin pictured one or two species……… . And, true enough, some species are endemic (especially on islands), while others have a rather large distribution range. I know that kind of stuff from South East Asia. You are absolutely right: more genital morphology should be done, urgently……… . A contact to an American specialist of Carribean terrestrial species would be phantastic! Again: thanks a lot for your trouble! Kind regards: wolf
there is still much doubt whether Caracolus marginella and Caracolus sagemon are two valid, different species at all. I did some research and meanwhile I think they are identical (same species, but with some amount of intraspecific variability). Anyway, "Caracolus" is the right genus, not "Pleurodonte". Reading the literature, it turned out that the term "semiaperta" refers to the umbilicus, which is half open (= semi-aperta) in Caracolus marginella semiaperta (in adult specimens). That´s the characteristic difference to Caracolus marginella marginella. "semiaperta", "rostrata" and other variants surely are no subspecies, but only different "forms" (= f.). So the correct term should be "Caracolus marginella f. semiaperta" (if the umbilicus is half open in adult specimens). The taxonomic status (f.) "rostrata" is right for specimens which have a pronounced "beak" at the outer margin of the aperture (lat. rostrum = beak).
What about pleurodonte excellens? I know this has nothing to do with the two species you mentioned above, but it made me curious as to whether they more correctly belong in the caracolus genus or pleurodonte?
Hi Cashell, thanks for your input . According to the definition of Pilsbry (Manual of Conchology), the shells of the genus Caracolus are keeled with no teeth in the aperture. So it's Caracolus excellens, not Pleurodonte excellens. There's some confusion in literature and www.
Pleurodonte has a basal tooth in the aperture (plus some additional folds, sometimes). If the tooth is lacking, the shell is not clearly keeled (last whorl more or less rounded). So it's Pleurodonte josephinae and Pleurodonte isabella, f.e. (not Caracolus).
Hello there, I hope you got what you wanted dear Wolf. I am new to the forum and I just got an African land snail and I tried hard but can't identify it, I just got pictures of it and actually registered here to get help from you guys on identifying my GALS. So how could I do it? Any of you guys could send me message so I can get him the pictures and help me find out what specie he is? Thanks a million! Good luck. Chriss