Vomeronasal organ of the North American river otter ( Lontra canadensis ): Morphological and evolutionary insights based on iodine‐enhanced computed tomography

The olfactory system plays a critical role in mammalian environmental perception, with some clades relying on an expanded accessory olfactory (vomeronasal) system (VNS) for social communication between conspecifics. Recent studies have begun to investigate how the VNS changes in response to or as part of ecological transitions. Several of these studies have identified trends of VNS-associated gene loss or regression in secondarily aquatic mammals. However, continuing discussion on genotype-phenotype correlation within the VNS means that greater effort should be made to investigate the morphology of the VNS in species where it remains poorly understood. Here, we use skeletal and soft-tissue data to demonstrate that the vomeronasal groove (VNG), an established osteological correlate for the vomeronasal organ (VNO) in bats and primates, is also a valid indicator for its presence in Caniformia. Additionally, we confirm the presence of the VNO in the secondarily aquatic North American river otter (Lontra canadensis) and compare its morphology with that of two closely related species, the semi-aquatic American mink (Neogale vison) and the terrestrial long-tailed weasel (Neogale frenata). This study expands the valid taxonomic scope of the VNG's proxy as an osteological correlate, confirms the presence of the VNO in the previously undescribed VNS of the North American river otter, and highlights the complexity of the mammalian accessory olfactory system.