Posted: Mar 24 2011
Stramonita canaliculata (Gray, 1839), Hays' Rock-shell
WoRMS (Nov 2025) recognizes ten species of Stramonita. One (S. buchecki) is unlikely to be a valid species. Six have distributions that do not include Florida. One of the six (S. haemastoma) was long, and still is in many publications and online sites, considered to be the comprehensive species name for a complex of species occurring in Europe and the western Atlantic. However, based upon several molecular studies WoRMS has replaced the species named S. haemastoma for the Stramonita found in Florida waters with three species elevated from subspecies status to full species status; S. canaliculata, S. floridana, and S. rustica. While molecular studies have validated that S. canaliculata and S. floridana are separate species, so far (as of Nov 2025) no one has come up with a definitive way to distinguish the two morphologically or based upon location.
Question to AI: Is it possible to distinguish between Stramonita floridana and Stramonita canaliculata?
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Response (11/24/25):
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No, it is very difficult or impossible to distinguish between Stramonita floridana and Stramonita canaliculata based on shell morphology alone, even in adults. These two species show significant overlap in sculptural variation, and molecular analysis is often needed for accurate identification. While traditionally, S. floridana was assigned to the Atlantic and S. canaliculata to the Gulf of Mexico, recent genetic findings indicate both occur in both areas.
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Why it's difficult to distinguish them:
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Morphological variation: The shells of both species are highly variable in shape and sculpture, making it hard to find consistent, defining characteristics.
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Geographic overlap: The species' ranges overlap, especially in areas like the Gulf of Mexico and parts of the Atlantic coast, which increases the chances of intermingling and hybridizing.
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Molecular studies: Scientists have found that even with DNA barcoding, re-evaluating the identities of specimens can be complex and requires comprehensive molecular and genetic studies for definitive answers.
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Ecological differences: While some researchers have suggested that S. floridana prefers more open oceanic environments and S. canaliculata prefers more estuarine shorelines, this is not a reliable method for distinguishing individual shells.
I have not been any more successful than others in ascertaining a definitive way to distinguish S. canaliculata from S. floridana. Since S. canaliculata is overwhelmingly dominant in NW Florida I have used only specimen(s) therefrom to represent it in the below slides.