| Summary: | Oceanic Islands are natural laboratories for the study of the processes and patterns of dispersion, colonization and ultimately of the appearance of new species. In the Northeast Atlantic, the archipelago of the Azores meets all the requirements to be considered one of the most isolated oceanic island systems. In general terms, the Azorean biota, as other oceanic systems, derives from dispersal chance events. For shallow-water marine benthic organisms, the main mechanisms to overcome the isolation by distance are rafting by non-planktonic life stages and through planktonic larval stages, both of which rely heavily on sea-surface currents to travel. However, and in spite of being under the influence of the western-intensified Gulf Current, the Azorean biota shows an opposite trend, being predominantly derived from the NE Atlantic and the Mediterranean. This apparent paradox has startled many marine biogeographers, who search for answers in the present-day faunal patterns together with those reconstructed through the past geological history of the archipelago. The present study attempts to further contribute to the knowledge of the marine fauna of the Azores, and its biogeographical relationships, using the echinoderms as a model. This animal phylum encloses a diverse group of strictly marine invertebrates found at all latitudes and depths. Furthermore, the echinoderms form one of the most conspicuous elements of both shallow- and deep-sea fauna in the Azores, and both in extant waters and among the fossiliferous outcrops of Santa Maria (37°N23’ 24°45’W), the oldest island in the archipelago. Thus, for a clear biogeographical background it was necessary to construct an updated catalogue of both local extant and fossil echinoderm fauna. During the International Workshops ‘Palaeontology in Atlantic Islands’, held in Santa Maria Island between 2002-2013, new material was collected from Lower Pliocene and Pleistocene deposits. The early Pliocene beds encompass the following taxa: Eucidaris tribuloides, Echinoneus cf. ...
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