ANATOMY AND SYSTEMATICS OF CARDIOLUCINA 



121 



The phylogenetic analysis shows that Cardiolucina lamothei and 

 C. rehderi are closer to the C. semperiana clade of species than to the 

 C. australopilula or C. eucosrnia clades. This suggests that the clade 

 containing C. lamothei-rehderi and C. semperiana had a widespread 

 Tethyean distribution prior to the (late Miocene) closure of the 

 connection between the Indo-Pacific and Atlantic Oceans. This is 

 confirmed by the occurrence of C. agassizi in the Middle Miocene of 

 south west Europe. The C. australopilula clade is restricted in 

 distribution to the central Indo-Pacific. The Miocene species C. 

 nuciformis Tate from South Australia is similar to the Recent C. 

 crassilirata from the same area suggesting a long occupancy. 



Acknowledgements. Ian Loch, Jerry Harasewych, Tom Schiotte, 

 Graham Oliver & Alison Trew, Philippe Bouchet & Rudo von Cosel, Dick 

 Kilburn, Robert Moolenbeek, Fred Wells & Shirley Slack-Smith, Hiroshi 

 Saito and John Slapcinsky generously provided access to material and loan of 

 specimens in their care. Thierry Backeljau kindly sent information about the 

 Dautzenberg collection. Philippe Bouchet & Rudo von Cosel provided 

 access to unpublished information and commented on the manuscript. We 

 thank Graham Oliver for discussion and nomenclatural advice. Additionally 

 we are grateful to David Cooper for the thin sections of C. australopilula, 

 Harry Taylor for fine macrophotography, Nick Hayes for printing of SEM 

 photographs and Alex Ball for translating some descriptions. 



REFERENCES 



CONCLUSIONS 



In this revision of the systematics ofCardiolucinawe have redefined 

 the genus and its type species and recognised eleven living species 

 from the tropical Atlantic and Indo-W. Pacific provinces. The previ- 

 ous lumping of many taxa into C. semperiana underestimated 

 species diversity. Table 3 provides a summary of the characters of the 

 recognised species as an aid to identification. Anatomical characters 

 are known for only two species, C. australopilula andC. semperiana. 

 Comparison with other genera is difficult because of the lack of 

 information, but Parvilucina has some similar characters, such as 

 the lack of mantle fusion at the posterior inhalant area, the connec- 

 tion of the ctenidia to the posterior mantle and the large visceral lobe 

 (Reid and Brand, 1986). Further work is needed to establish the 

 distribution of these characters in other lucinid taxa. 



Although the earliest Cardiolucina would seem to be the Eocene 

 species C. ligata (Cossmann & Pissarro), the fossil record, apart 

 from C. agassizi which is common in the middle Miocene of Europe, 

 is rather scanty. The only species we can confirm are Cardiolucina 

 nuciformis (Tate) from the Miocene and, from the Pliocene, C. 

 gonzalesi (Shuto) and C. polli (Icke & Martin). This paucity of 

 records is unsurprising because, even in Recent faunas, these small 

 lucinids are neglected. 



The problems encountered during this systematic revision reflect 

 the current state of systematics within the family Lucinidae. Many 

 genera are defined only by a small number of shell characters, type 

 species of genera are often inadequately described and, moreover, 

 their characters are often ignored by systematists. Species diversity 

 is often greater than realised because taxa have been shoe-horned 

 into a small number of 'well-known' names. Relationships between 

 genera are generally unknown and rigorous phylogenetic analyses 

 are lacking. Bretsky (1970, 1976) produced a phenetic/phylogenetic 

 analysis of lucinid genera, with possible phylogenies for her various 

 lineages. Unfortunately, there are problems with these phylogenies 

 because she lumped together distinct genera and confused type 

 species, for example, using for Bellucina characters of Radiolucina 

 amianta instead of the type species B. eucosrnia. Moreover, there is 

 no anatomical or biological information available for the vast major- 

 ity of species, especially those from the Indo-Pacific province. 

 Recent studies on the chemosymbiosis of lucinids have focused on 

 a small number of species from the Caribbean and temperate north 

 Atlantic and Pacific (reviewed in Fisher, 1 990, Le Pennecefa/., 1995), 

 but biological information from these studies has yet to be integrated 

 into lucinid systematics. Systematic and phylogenetic studies should 

 be providing the framework to test hypotheses concerning the 

 evolutionary history and radiation of the Lucinidae, but, at present, 

 these are inadequate. 



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