The Azores, Madeira, Selvagens, Canary Islands and Cabo Verde are commonly united under the term “Macaronesia”. This study investigates the coherency and validity of Macaronesia as a biogeographic unit using six marine groups with very different dispersal abilities: coastal fishes, echinoderms, gastropod molluscs, brachyuran decapod crustaceans, polychaete annelids, and macroalgae. We found no support for the current concept of Macaronesia as a coherent marine biogeographic unit. All marine groups studied suggest the exclusion of Cabo Verde from the remaining Macaronesian archipelagos and thus, Cabo Verde should be given the status of a biogeographic subprovince within the West African Transition province. We propose to redefine the Lusitanian biogeographical province, in which we include four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores, and a new ecoregion herein named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands.

51Massive fossil shell accumulations require particular conditions to be formed and may 52 provide valuable insights into the sedimentary environments favouring such 53 concentrations. Shallow-water shell beds appear to be particularly rare on reefless 54 volcanic oceanic islands on account of narrow, steep and highly-energetic insular 55 shelves where the potential for preservation is limited. The occurrence of an exceptional 56 coquina (Pedra-que-pica) within the Miocene-Pliocene deposits of Santa Maria Island 57 (Azores), therefore provides a rare opportunity to understand the conditions that led to 58 the formation and preservation of a massive shell bed at mid-ocean insular setting. This 59 study provides a detailed analysis regarding a 10-11 m-thick bivalve-dominated fossil 60 assemblage exposed at Pedra-que-pica on Santa Maria Island in the Azores. Integration 61 of taphonomical, palaeoecological and sedimentological observations are used to 62 reconstruct the genesis of the coquina bed and related events, and to discuss why such 63 exceptional sedimentary bodies are so rare on shelves around reefless volcanic oceanic 64 islands. 65 The sequence at Pedra-que-pica demonstrates a complex succession of sedimentary 66 environments in response to the drowning of an existing coastline during a period of 67 rapid sea-level rise. The Pedra-que-pica shell bed incorporates storm-related materials 68 and possible debris falls that originated nearby in a shallow and highly productive 69 carbonate factory. Deposition took place below fair-weather wave base, at around 50 m 70 depth, as inferred from the overlying volcanic succession. The preservation of this 71 coquina was favoured by deposition on a platform laterally protected by a rocky spur, 72 combined with rapid burial by water-settled volcanic tuffs and subsequent volcanic 73 effusive sequences. The recent exhumation of the deposit is the result of island uplift 74 and subsequent erosion.75 4 76 77

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The Pleistocene (Eemian) outcrops of Lagoinhas and Prainha, located at Santa Maria Island (Azores), were investigated and their fossil mollusc content reported. These studies revealed that the last glaciation affected two groups of molluscs: the ‘warm‐guest’ gastropods with West African or Caribbean affinities (e.g. Conus spp., Cantharus variegatus, Bulla amygdala, Trachypollia nodulosa) and shallow bivalve species mainly associated with sandy habitats (Ensis minor, Lucinella divaricata, and probably Laevicardium crassum). In this paper we focus on this group of bivalves, which has since locally disappeared from the Azores. We relate the local disappearance of these bivalves in the Azores with the lack of sand in the shelf. The specific characteristics of the Santa Maria shelf combined with the sea‐level drop during the Weichselian prevented deposition of the lowstand deposits and permitted erosion of the previous ones, leaving the shelf without a sediment cover. Copyright © 2008 John Wiley & Sons, Ltd.

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