The successful application of multivariate statistical techniques as well as geometric morphometry to the study of taxonomic problems encourages the use of these methods for solving problems arising from lack of internal morphometric characters in ostracods.
The results indicate that the geometric measurements were marginally more helpful in differentiating the three studied species, whereas the distance measures were not. However, the distance measurements can help differentiate males from females.
The thin-plate spline results suggest that C.? sp. is a distinct species, which is more similar to D. ismaili than it is to D. omarai. Additionally, the deformation between D. omarai and D. ismaili is not as strong as one might have expected. This may be due to one of the following: 1) the older species (Digmocythere omarai) is the ancestor of the younger (D. ismaili) as suggested by Boukhary et al. (1982); or 2) these two species could be two morphs of one species.
Because the dorsal zone is more deformed in the warping of D. ismaili into D. omarai than the other zones, I therefore, support the first suggestion that the second species is the ancestor of the first. The dorsal margin contains the hinge which in general tends to evolve towards shorter length relative to the length of the carapace (Kaesler In: Boardman et al. 1987). This is the present case, where Digmocythere ismaili has shorter hinge distance (G; in the measurements of the present study) relative to the carapace length than Digmocythere omarai.
Finally, this study points out that benefits can be expected by applying geometrical morphometrics and, as an auxiliary tool, multivariate statistical analyses for solving problems in the field of systematics.