The mollusc associations of 29 hard-substrate localities in the Northe
rn Bay of Safaga (Red Sea, Egypt) were studied. The hard substrates we
re classified into 7 types: reef flats, intertidal rock bottom, very s
hallow subtidal conglomerate, Porites carpel, faviid carpet, platy scl
eractinian association, Sarcophyton carpet. Based on a cluster analysi
s the molluscs of these hard substrates can be classified into 5 group
s: Group A is dominated by Dendropoma maxima, Chamoidea and Tridacna m
axima, group B by Pedum spondyloideum, T. maxima and Coralliophila ner
itoidea, group C by Chamoidea and Cerithium ruppelli, group D by Modio
lus auriculatus, Chamoidea, Morula granulata and Nerita albicilla and
group E by Chamoidea and Pitar hebraea. The latter group contains only
samples which are generally poor in molluscs. Group A molluscs are di
agnostic for reef flats, group B for Porites and faviid carpets, group
C for Sarcophyton carpets and group D for tidal/shallow subtidal rock
substrates. The different hard substrates are therefore characterized
by diagnostic mollusc associations and some of them could also be ide
ntified in the fossil record.