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.

Oceanic islandssuch as the Azores in the mid-North Atlanticare periodically exposed to large storms that often remobilize and transport marine sediments along coastlines, and into deeper environments. Such disruptive events create depositsdenominated tempestiteswhose characteristics by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high-energetic environments, such as the insular shelves of open-sea volcanic 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