Biogeographic Distribution
Members from the family Rissoidae have been found in seas all around the world, ranging from polar to temperate latitudes (Ponder, 1985).Genera such as Alvania, which have planktotrophic larvae, have extensive distributions that are associated with oceanic circulation (Ponder, 1985). Other genera, such as Attenuata, have direct development which tends to limit the organisms to a smaller geographic distribution (Ponder, 1985). This is argued in a paper by Avila (2013), who states that organisms with direct development may have the ability to raft. This may be achieved by algae breaking loose while the species attached (Ponder, 1985).
The distribution of two genera, that have similar morphological characteristics to the unidentified Rissoidae, were found on the Encyclopedia of Life. The distribution of the first genera, Voorwindia, is shown in Figure 4 below. This figure shows that Voorwindia has high distribution on the East coast of Australia, with some individuals also found around Japan. Figure 5 shows the distribution of the genus Setia has been found in seas north of Africa, in high abundances. From the distributions portrayed by the Encyclopedia of Life it would suggest that the unknown Rissoidae is more likely to be from the genus Voorwindia than Setia.
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