Mericella was introduced by Thiele as a section of the subgenus Narona H. & A. Adams, 1854. but that placement cannot be maintained because Narona is a Panamic-Pacific genus (Petit, 1975: 388).
From the Western Indian Ocean are known: Mericella paschalis (Thiele, 1925) from Zanzibar Channel and Bazaruto, Mozambique; Mericella jucunda (Thiele, 1925), from Dar es Salaam, Tanzania and Mericella bozzetti Petit & Harasewych, 1993 from off Somalia.
Olsson & Bayer (1972) introduced the genus Gerdiella, type species (O. D.) Gerdiella gerda Olsson and Bayer, 1972, for three Caribbean species (Gerdiella cingulata Olsson and Bayer, 1972; G. gerda; G. santa) with the remark: "most similar of these is Mericella Thiele, 1929, from east African waters... It seems unwise to refer our species to Mericella in view of our incomplete knowledge of its type species" (Olsson & Bayer, 1972: 875). And also: " Mericella is perhaps the more likely possibility with which Gerdiella may be congeneric. However, definite reference of our Caribbean shells to Mericella, as first considered, would be premature since it would imply a direct relationship between our Caribbean species and an imperfectly known species from the Indian Ocean, an expression of a degree of knowledge on our part that we do not possess " (Olsson & Bayer, 1972: 876). Lima et al. (2007: 100) stated that "the geographical grouping of Mericella, with all known species being from off eastern Africa, and Gerdiella, with all known species being from the western and southern Atlantic, is obvious".
There is no consensus yet as to Mericella and Gerdiella being synonyms (Petit & Harasewych, 1993; Verhecken & Bozzetti, 2006; Lima et al., 2007). According to Kaicher (1978, card 1953) Cancellaria corbicula Dall, 1908, from off California, "is usually placed in the genus Mericella but seems to resemble more closely the Caribbean Gerdiella". Yet, Lima et al. (2007: 100) do not consider C. corbicula to belong to Gerdiella and prefer to keep its generic placement in doubt. That discussion is now revived by the description of Mericella rosadoi n. sp., which has almost all characteristics of the Atlantic Gerdiella alvesi Lima, Barros & Petit, 2007 (see further). Phylogenetic analysis may bring the answer one day. Mericella zhangsupingae S. Zhang & Wei, 2018, from the Dongsha Islands, South China Sea, has now extended the distribution area of Mericella to the northwestern Pacific. The genus Gerdiella is as yet unknown in the Tertiary of Caribbean and Panamic areas (Petit, 1983: 250).