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Several species of bivalves belonging to families which are typically associated with reducing conditions, like those observed at methane seep sites, have been obtained in recent explorations of the Caribbean Sea margin off the coast of Colombia. The material has been collected at depths of around 500 m west of the Magdalena and Sinú deltas, located in the Sinú–San Jacinto fold belt. These bivalves correspond to the families Vesicomyidae (Calyptogena ponderosa, Vesicomya caribbea and Ectenagena modioliforma), Lucinidae (Graecina colombiensis and three unidentified species of Lucinoma), Solemyidae (Acharax caribbaea) and Thyasiridae (Conchocele bisecta). In addition, for the first time off Colombia empty tubes of vestimentiferan polychaetes, belonging to the family Siboglinidae, were collected. At some of these sites the presence of authigenic carbonates has been observed together with the biological material. Although the obligate seep fauna generally contains relatively few and endemic species, a large suite of accompanying heterotrophic species (here we report only the molluscs) has been found at the seep sites. The occurrence of carbonates, the geological characteristics of the area and the new biological evidence confirms the presence of methane seep ecosystems in the Caribbean Sea off Colombia.

Fifteen species of sea anemones (Cnidaria, Actiniaria) have been recorded so far in the Colombian Caribbean, comprising approximately 28% of the total number of known species in the Caribbean Sea. Most species recorded are associated with coral reef communities. However, in the region, no records of sea anemones are known from areas with high sedimentation conditions as is characteristic along the coastline of the Atlántico Department, in Colombia. In this area, organisms are exposed to a high degree of turbidity and sedimentation (~143.9x10 6 t year -1 ) as a result of their proximity to the Magdalena River mouth and the 26 micro-basins that fl ow along its coastline. Several observations and collections were made on soft bottoms, rocky, and artifi cial substrates in the sectors of Puerto Velero and Caño Dulce to determine the fauna that exist under these conditions. Four species of sea anemones were found belonging to the families Actiniidae and Aiptasiidae, and images from living specimens and cnidae are provided.Bunodosoma cavernatum and Exaiptasia diaphana are here recorded for the fi rst time from the Colombian Caribbean. An updated list of sea anemones in the Colombian Caribbean, now comprising 34 taxa (i.e., 21 species and 13 identifi ed at supra-specifi c levels), is provided.

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Despite its importance as the larger component of the modern and Cenozoic brachiopod faunas in the Caribbean region, the ecology and habitat preferences of the terebratulid Tichosina remain poorly understood. We compiled field observations from multiple sites in the Caribbean of Colombia (i.e., San Bernado Bank, Bahia Honda-Guajira, Puerto Escondido, Joint Regime Area Jamaica-Colombia) and data from the R/V Pillsbury Tichosina in deep-sea coral bottoms of the Caribbean 2 program, indicating that Tichosina may have close ecological ties with deep-water corals. In addition, we reviewed literature sources on Cenozoic sediments in the Dominican Republic and found tentative evidence that such ecological ties could have existed since at least the Pliocene. These observations are reminiscent of the Gryphus-anthozoan association observed in the modern Mediterranean continental margin. Understanding to what extent the brachiopod Tichosina is linked to deep-water habitats has implications for the recognition of deep-water macrobenthic communities in the Cenozoic rock record of the Caribbean.