Conservative Nature of Biomineral Structures as a Challenge for the Cladistic Method of Phylogeny Reconstruction (Illustrated by Two Groups of Dinosaur Eggs)

Abstract

Analysis of the results of involvement of eggshell structure and egg morphology traits in the cladistic analysis of dinosaur (primarily, theropod) phylogeny revealed the subjective character of trait state assessment upon the construction of a matrix. The example of two groups of elongated dinosaur eggs (Elongatoolithidae and Prismatoolithidae) has been used to demonstrate that the motivation to confirm the correctness of the theropod (taxa that generated the eggs) cladogram often resulted in a biased interpretation of trait modality – for instance, to the detection of avian traits in the structure of eggshell, eggs, and nests. We showed that it was actually impossible to demonstrate the presence of these traits in the material studied. It has been noted that uncritical attitude to the matrix leads to a loss of important biological information, including the information related to the patterns of morphogenesis evolution.