Additional Elements in the Posterior Part of the First and Second Upper Molars in Lasiopodomys (Stenocranius) gregalis (Rodentia: Cricetidae)

It was found that the variability of additional elements in the posterior part of the first and second upper molars in L. gregalis forms a morphological module with a hierarchical structure. This module is designated as an atypical form (Atypical Form), and its phenotype as AF. The phenotype of the typical form is designated as tf (typical form). The main component of modular variability is an increase in the frequency of individuals with AF phenotype with age. The severity of this phenotype also increases with age. The presence of the AF phenotype in individuals is determined monogenously. Individuals with the AF phenotype are dominant heterozygotes or homozygotes. Which phenotype (tf or AF) the dominant heterozygote implements may depend on the influence of modifier genes. The revealed morphological module of the presence of additional elements in the posterior part of the first and second upper molars has a genetic basis.