ABSTRACT
The paper describes the phenomenon of substitution of the reduced M2 with a tooth of a complex structure in the American mink Neovison vison Schreber. The anomaly is observed on three skulls out of the 574 examined (0.52%) and is characterized by a clear localization, identical structure, and symmetrical manifestation. Atypical molars have two roots, equally well-developed paraconid, eokonid, hypoconid, and a less pronounced metaconid. Some possible hypotheses for the anomaly that are considered include disruption in the development of the dental germ, mutation, and phenotypic expression of genes that are characteristic of plesiomorphic species of mustelids. The substantiated viewpoint is that the cause of this phenomenon may be the "awakening of dormant genes" as a result of destabilizing selection and hybrid dysgenesis in the area of contact of farm and feral American minks.
