For Suarez-Morales & Alvarez-Silva (2001, p.187) the main difference between the type specimens and the Mexican specimen is the size; this is not a factor with strong taxonomic value, hence, the size of the Mexican female of this species merely increases the known range of size variation for C. tumorifrons; the slight differences between the Mediterranean and Mexican specimens are not sufficient to warrant erection of a new taxon (see Table 1). Isaac (1974) assumed that female and male belonged to a single species; however, this may have been misleading because the only way to link males and females of one monstrilloid species is to find them in the same host or verify that they share distinctive diagnostic characters ; morphologic characters that may link both sexes include striation of the head ((see in Suarez-Morales & Escamilla, 1997) and the general structure of the eyes; another feature whose value to link sexes is the branching pattern of Grygier & Ohtsuka's (1995) distal setae of the distal segment . A1 (setae b1-b-3); these are distaly branched in male C. tumorifrons (Suarez-Morales, 1999) and unbranched in the assigned female (Isaac, 1974). Althrough the Mexican female seems to represent C. tumorifrons, there is the possibility that it belongs to another species. In 2009, Suarez-Morales & Morales-Ramirez (2009, p.1264) ceate Cymbasoma guerrerense species.
After Suarez-Morales & al. (2017, p.1817) this new species was originally described as C. tumorifrons by Isaac (1974) from Emborios Bay (Aegean Sea). He determined that the males and females collected belonged to the same species, based on its co-occurrence in the same sample. In the redescription of the males, Suarez-Morales (1999) argued that the name, published by Isaac (1974) was, nomenclaturally unavailable and it was explicity deemed as a nomen nudum there. Cymbasoma tumorifrons have to be attributed to Suarez-Morales (1999). This name, however, exclusively refers to the male type specimens, thus excluding the females mentioned by Isaac (1974). The adult females designated as allotype and paratypes by Isaac (1974) are not part of the type specimens of C. tumorifrons, and, thus, represent an undescribed species. A redescription of these female specimens was published by Suarez-Morales (2002), who art that time attributed these females as C. tumorifrons based on Isaac's type specimens, plus a female found in Toulon Bay. A comparison of the original illustrations by Isaac (1974) and Suarez-Morales (2002) redescription of these female specimens from the Aegean Sea and Toulon Bay allowed us to determine that our specimen from Trieste clearly belongs to the C. mediterranea.
Cf Table 2 from Lian & Tan (2019) in C. cheni.