Twenty-seven well-preserved, adult specimens from the three studied ostracod forms (14 males and 13 females; 12 specimens of D. ismaili, 6 specimens of D. omarai and 9 specimens of C.? sp.) were selected for multivariate morphometrics. The measurements for the canonical variate analysis are: the length of the carapace (L), the height of the carapace (H), the distance from the eye tubercle to the maximum end of the posterior margin (P), the distance from the eye tubercle to the maximum end of the ventral margin (V), and the length of the hinge (G). These measurements were taken based on SEM photographs of the specimens.
Eleven landmarks were selected for the eigenshape analysis and the thin plate spline and relative warps analyses (Figure 3): the mid-point along the antero-ventral margin (1), the maximum end of the anterior margin (2), the mid-point along the antero-dorsal margin (3), the location of the eye tubercle (4), the end of the hinge from the posterior side (5), the mid-point along the postero-dorsal margin (6), the maximum end of the posterior margin (7), the mid-point along the postero-ventral margin (8), and three landmarks at points of inflection of the ventral margin (9, 10, 11) and are therefore not as well established as the fixed-points (fixed-point here is used in spirit with the topographical surveying terminology embodied in the concept of landmarks).
These landmarks were digitized on the basis of SEM photographs using a computer program by Rohlf (1998a). Note that the observations of the studied left views of carapaces were rotated by 180 degrees to achieve compatibility with the studied right views of carapaces. Eigenshape analysis is usually based on a more thorough sampling of the outline of a specimen, but these 11 landmarks capture most of the aspects of the shape so they were used to allow more direct comparison with the relative warps results.