Application of morphometric techniques for taxonomic revision of Berabichia oratrix (Orłowski, 1985) (Trilobita, Cambrian) from the Holy Cross Mountains, Poland

Detailed analysis of c. 900 trilobite specimens from the Cambrian Series 2 of the Holy Cross Mountains in Poland, assigned hitherto to Comluella oratrix Orłowski, 1985 and Comluella igrzycznae Orłowski, 1985, has shown that the two species constitute in fact a monospecific assemblage representing Berabichia oratrix (Orłowski, 1985). The differences pointed out in the original diagnoses are obviously caused by taphonomic processes. To test the hypothesis of a monospecific assemblage, six sagittal and exsagittal and five transverse parameters were measured and calculated for 182 best-preserved cranidia; from this dataset, 121 cranidia with the complete set of measurements were subjected to bivariate and multivariate morphometric analyses and discriminant analysis. Results of the morphometric analysis point to the significant role of tectonic deformation in the variation of the studied sample that could have led Orłowski (1985) to distinguish two separate species. Application of graphic techniques on photographs of distorted specimens lying in different directions with regard to the stress field allowed to obtain specimens statistically indistinguishable in terms of their sagittal and transverse proportions, thus confirming the tectonic overprint on the morphology of the analyzed trilobite sample.