Local disappearance of bivalves in the Azores during the last glaciation

Abstract

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.

ORIGINAL ARTICLE: Mass extinctions in the Azores during the last glaciation: fact or myth?

“…Fossils of 20 species (16 gastropods and 4 bivalves) that are reported from the Pleistocene fossil record of Santa Maria Island (Azores) (Ávila et al. , 2002, 2008a) are no longer present anywhere on the archipelago (Table 1).…”

“…We constructed a table with all bivalve and gastropod species present in the Pleistocene of the Azores but which are no longer present in the archipelago, including notes on the type of habitat and bathymetric range of these species, reported from the Pleistocene fossil record of Santa Maria Island, using data adapted from Ávila et al. (2002, 2008a) (Table 1).…”

“…We consider these as extirpated species, that is, species that locally disappeared from the archipelago as a result of the last glaciation. Data modified from Ávila (2005) and Ávila et al. (2002, 2008a,b) were also used to compare the Pleistocene fossil record from Prainha and Lagoinhas (Santa Maria Island, Azores), with the Recent molluscan fauna of the Azores (Ávila, 2000, 2005) (Table 2).…”

Diversity, distribution and ecology of benthic molluscan communities on the Portuguese continental shelf

“…The validity of species name was checked in the WoRMS website (Bouchet and Gofas, 2013) and ecological preferences in those references and others considered suitable (e.g. Antoniadou et al, 2005;Ávila et al, 2008;Bouchet and Gofas, 2013;Duff et al, 2009;Krylova, 2006;Prena et al, 1999;Rodríguez and Sanchéz, 1997).…”

“…Total abundance (A), total frequency (F), sediment type and bathymetric range of the mollusks species collected in the soft-bottom sediments of the Portuguese continental shelf and habitat preferences and biogeographic distribution according to the literature (e.g. Antoniadou et al, 2005;Ávila et al, 2008;Bouchet and Gofas, 2013;Duff et al, 2009;Krylova, 2006;Macedo et al, 1999;Prena et al, 1999;Rodríguez and Sanchéz, 1997;Tebble, 1976). Legend: n.a.…”