Thyasiroidea (Mollusca: Bivalvia) from the mud volcanoes of the Gulf of Cadiz (NE Atlantic) Author Rodrigues, Clara F. Author Oliver, Graham Author Cunha, Marina R. text Zootaxa 2008 1752 41 56 journal article 49677 10.5281/zenodo.274249 b4d292b4-0c92-42c7-a47b-9a3577bd28be 1175-5326 274249 Thyasira tortuosa ( Jeffreys, 1881 ) (Fig. 27) Material examined . One live-collected specimen, TTR16 cruise, station AT 622Gr, Porto mud volcano, Gulf of Cadiz, 35º 33.773N , 09º 30.416W , 3902 m , 3 June 2006 ( DBUA 00830.01). Remarks. The only specimen examined is provisionally identified as Thyasira tortuosa and has the characteristically compressed and anteriorly expanded outline noted by Payne and Allen (1991) . The shell from Gulf of Cadiz ( 5.5 mm ) is much larger than any of the shells described by these authors ( 3.2 mm ) and comes from a greater depth: 3902m whilst the maximum given by Payne & Allen (1991) was 2359 m . Dufour (2005) did not examine this species but the Gulf of Cadiz specimen has a Type 2 gill with both demibranchs. The gills are rather thick and have the same appearance as the ones that exhibit strong bacterial symbiosis such as T. flexu osa and T. gouldi .