Implications of the Discovery of a Stag Moose (Cervalces sp., Cervidae) Skull with Antler Beams of Different Lengths

A stag-moose Cervalces sp. (Cervidae) skull with antler beams of substantially different lengths has been analyzed. This skull was found in the lower reaches of the Yana River along with the lower jaw and four vertebrae. Its geological age has been assigned to the range from the very end of Eopleistocene to the first half of the early Neopleistocene. The unequal lengths of the beams in the individual analyzed was reproduced during each antler regeneration throughout the animal’s life. This may be indicative of the genetic nature of the phenomenon, even though a nongenetic cause of this disproportion is also possible, as many field observations and experimental data demonstrated frequent asymmetric disturbances in antler growth in modern deer due to injuries, especially forelimb injuries. If the genetic hypothesis is true, such an anomaly may be a manifestation of intensive form genesis, a putative adaptive reaction to the first substantial cooling of the climate in the Pleistocene. Antler beam proportions are the most valuable criterion for species and subspecies taxonomy and diagnosis of fossil moose. The case described by us does not render this trait useless, since the case is exceptionally rare. However, this genetic anomaly may be indicative of an increase in evolutionary trait variability during periods of significant climate change, which should be borne in mind when the morphology of animals that lived during such epochs is interpreted.