Olfaction in the tammar. (a) The olfactory apparatus of the tammar showing the pattern of vomeronasal receptor projections to the accessory olfactory bulb with the VN2 receptor cells (expressing Goα) projecting to all parts of the vomeronasal nerve layer (which may also be the case for the VN1 receptor cells (expressing Giα2). This projection pattern may reflect an intermediate type to the 'segregated type' and the 'uniform type' so far described. AOB, accessory olfactory bulb; GL, glomerular layer; GRL, granule cell layer; MOB, main olfactory bulb; MTL, mitral tufted cell layer; VNL, vomeronasal nerve layer; VNO, vomeronasal organ; VN1R and VN2R, vomeronasal receptors 1 and 2. (b) Olfactory receptor (OR) gene family in the tammar. The families of the OR gene repertoire. Neighbor joining tree of 456 full-length functional OR genes was rooted with opossum adrenergic β receptor. Only a few OR gene families (14, 51 and 52) have members that are most closely related to each other, whilst most other families have a high degree of relatedness to other families.