Thalassonerita is a monotypic genus of sea snails, marine gastropod mollusks in the family Neritidae.

[2] T. naticoidea is endemic to underwater cold seeps in the northern Gulf of Mexico and in the Caribbean.

[4] T. naticoidea lives in cold seeps in the northern Gulf of Mexico and in the accretionary wedge of Barbados in the Caribbean[5] in the upper continental slope, in depths from 400 to 2100 m.[5] Minimum recorded depth is 541 m.[6] Maximum recorded depth is 1135 m.[6] Examples of localities include: T. naticoidea has a shell that can be closed with a calcareous operculum.

[8] T. naticoidea lives at deep-sea cold seeps where hydrocarbons (oil and methane) are leaking out of the seafloor.

[9][12] T. naticoidea cannot move over mud or on soft sediments,[13] and usually lives on beds of Bathymodiolus childressi mussels.

[15] This was the first ultrastructural description of formation of yolk in today's clade Neritimorpha.

[12] Veliger larvae are hatched from eggs after four months of development from May to early July.

[12] There lives a fungal filamentous ascomycete (phylum Ascomycota) species as a commensal on the gills of T.

[10] When this discovery was published in 1999, it was the first such association between fungus and gastropod from underwater seep community.