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Posted: Sep 27 2007

 Echinolittorina of Florida (subgenus Amerolittorina)

                                                                            By Marlo F. Krisberg
                                                                               August 19, 2009

On July 5, 2007 I updated my presentation of Florida Echinolittorina to reflect the then current results of David G. Reid’s decades-long work on the Littorinids. At that time the Florida species that had previously been classified as Nodilittorina or Littorina were unified under the genus Echinolittorina and the senior names for the Florida shells were as follows:

E. ziczac (Gmelin, 1791)
E. angustior (Mörch, 1876)
E. riisei (Mörch, 1876)
E. interrupta (C. B. Adams in Philippi, 1847)

[Note: L. lineolata Orbigny, 1840 listed in Abbott (American Seashells 1974) had since been confirmed as restricted to Brazil/Uruguay. N. mordax Bandel & Kadolsky, 1982 presented in Redfern (Bahamian Seashells 2001) has since been accepted as a junior synonym of E. riisei.]

As I indicated in 2007 “David is currently working on a monograph of all the Atlantic Echinolittorina, together with anatomical characters for their discrimination. I’ll post a notice when it’s published. 
Well, David’s monograph has now been published:

Reid, D.G., 2009. The genus Echinolittorina Habe, 1956 (Gastropoda: Littorinidae) in the western Atlantic Ocean. Zootaxa 2184: 1-103. Aug. 6.

David has grouped the 10 known living Littorinids in the western Atlantic within the genus Echinolittorina and, within the genus, separated the 10 into four subgenera as follows:

Fossarilittorina Rosewater, 1981
     E. meleagris (Beck in Potiez & Michaud, 1838)
     E. mespillum (Mühlfeld, 1824)
Lineolittorina Reid, 2009 (new subgenus)
     E. lineolata (d'Orbigny, 1840)
Amerolittorina Reid, 2009 (new subgenus)
     E. ziczac (Gmelin, 1791)
     E. jamaicensis (C. B. Adams, 1850)
     E. interrupta (C. B. Adams in Philippi, 1847)
     E. placida Reid, 2009 (new species)
     E. angustior (Mörch, 1876)

Echinolittorina Habe, 1956
     E. tuberculata (Menke, 1828)
     E. vermeiji (Bandel & Kadolsky, 1982)

The shells that have been the subject of my past presentations and this one are only those within the subgenus Amerolittorina occurring in Florida. David’s researches have continued to clarify the status of these shells and resulted in several significant changes, as follows:

1. Echinolittorina jamaicensis (C. B. Adams, 1850) is established as the senior name to E. riisei and N. mordax. Reid recalls that Bandel & Kadolsky (1982) had discarded this earlier name when dividing this species into three (N. riisei, N. glaucocincta, and N. mordax) solely on the basis of striking differences in the radula rather than diagnostic differences in the shells. They commented that the characters of these shells so overlapped that "these shells cannot be distinguished ... without studying the radula and the spawn.” However, Reid’s work found that radular variation among these shells was very marked but not sufficiently or consistently differentiated between them so as to justify speciation. Similarly, he found no consistent differentiation between DNA data, shell morphology, reproductive anatomy, nor geographic distribution.

2. Echinolittorina placida Reid, 2009 is established as a new species and replaces E. interrupta for the shells found in Florida and along the American Atlantic and Gulf coasts. E. interrupta is restricted to the continental shores and high islands of the Caribbean Sea south of Cuba. David separated these two species based upon shell morphology, differences in the anatomy of the penis, DNA data, and geographic separation.

So, with David’s latest discoveries we still have the four similar Echinolittorina, now in subgenus Amerolittorina, in Florida to deal with, but we have new names for two of them:

                                                                 E. ziczac (Gmelin, 1791)
                                                                 E. angustior (Mörch, 1876)
                                                                 E. jamaicensis (C. B. Adams, 1850) (formerly E. riisei)
                                                                 E. placida Reid, 2009 (formerly E. interrupta)

David provided enhanced information to help in distinguishing among these shells. I have updated the below descriptions where he has provided more helpful information. Overall, distinguishing a particular shell for placement within the correct species name (particularly E. jamaicensis and E. placida) will remain difficult. As David freely admitted when helping me distinguish specific shells, “precise definitions of the shell characters of these species are hard to make; it is almost always possible to find exceptions to rules if you compare single specimens.” Differences are subtle, variations frequent and overlapping; so, a lot of experience, exposure to many shells, and confirmation of identification is required to develop the expertise to reliably separate these shells.

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