| Summary: | Among living cervids, the moose or elk ( Alces alces ) is among the most distinctive for its enlarged proboscis. Despite over a century of scientific inquiry into the ecology and evolution of this species, the origin and function of its proboscis remain unclear. An ability conferred by the proboscis is closure of its nares, which the North American moose performs while diving for sodium‐rich aquatic vegetation. This is found in combination with elongated metapodials and long, splayed phalanges for walking on soft, marshy ground and cylindrical shape of the femoral head for greater mobility of the hip joint when walking over uneven surfaces as in closed swampland habitats. We investigated the anatomical basis and evolutionary history of the proboscis among moose by examining the soft‐ and hard‐tissue morphology of extant (i.e., dissected head and dry skulls) and extinct material (fossil Cervalces crania). The moose head was provided as a result of a vehicular accident while dry and fossil crania were studied from osteological collections from the Division of Vertebrate Paleontology and Mammalogy of the American Museum of Natural History. Results suggest that, rather than being a direct adaptation to aquatic foraging, the proboscis likely arose in a multi‐step process initiated when ancestral moose populations lost their rhinarium as an adaptation to selective browsing, freeing the external nose from the now mobile upper lip. Further selective pressures influencing ancestral moose populations in closed, marshy environments with poor visibility may have favored enhanced olfactory acuity provided by the proboscis, which appears to separate inspiratory airflow into superior olfactory and inferior respiratory columns via an elongated cartilaginous ridge emerging from the lateral wall of the anterior nasal cavity and meeting the inferior concha. Enhanced olfaction would be adaptive for predator avoidance among calving females and perceiving sociosexual signals during rutting season. Further analysis of the nasal cavity ...
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