Morphological plasticity and genetic flexibility in a Cambrian trilobite Available to Purchase

Morphometric analysis suggests that the uppermost Cambrian trilobite Dikelocephalusminnesotensis possessed a developmentally flexible genotype. Patterns of intraspecific variation in Dikelocephalus contrast with those seen in post-Cambrian trilobites. These results are consistent with other evidence suggesting that genetic systems were less strongly canalized during the Cambrian than in later times. Intraspecific variation in Dikelocephalus is partitioned into two components; one ontogenetically related, the other ontogenetically invariant. Both show a mosaic pattern of interpopulational variation. Slight heterochronic shifts are responsible for some differences between populations, but most characters appear to vary independently.