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■ SUMMARY
The mesogastropod Littorina littorea
(Linné, 1758) in Iceland:
PALAEOBIOGEOGRAPHYAND MIGRATION
The periwinkle Littorina littorea (Linné, 1758)
has not been found living at present in Iceland
The only confirmed occurrence of the species in
Iceland is in the Middle Pleistocene upper littq
ral conglomerate in Búlandshöfdi, Snæfellsnes
west Iceland. These layers were deposited dur-
ing an interglacial, slightly older than 1.1 Ma.
The species apparently evolved from the Pacific
L. squalida Broderip and Sowerby, 1829, during
the trans-Arctic-North Atlantic migration from
the Pacific as a result of cooling. The oldest fos-
sil occurrence of the species is in the British Red
Crag, 2.4-2.55 Ma old, and it has not been found
in the Pliocene Tjörnes deposits in north Iceland
which are older than 2.6 Ma. This indicates that
the species separation postdates the deposition
of the uppermost Serripes Zone of Tjörnes, af-
ter the tide of the migration wave passed Iceland
but before it reached the North Sea area and Brit-
ain.
PÓSTFANG HÖFUNDA /AUTHORS'ADDRESS
Ólöf E. Leifsdóttir
Netfang/e-mail: oel@rhi.hi.is
Leifur A. Símonarson
Netfang/e-mail: leifuras@raunvis.hi.is
Raunvísindastofnun Háskólans
/Science Institute
Jarðfræðahús Háskólans
IS-101 Reykjavík
110