In many species, the rhinarium has a mid-line groove (cleft)the philtrumand a wrinkled (crenellated) surface. The rhinarium is a separate sense organ: it is a touch-based chemosensory organ that connects with a well-developed vomeronasal organ (VNO). The rhinarium is used to touch a scent-marked object containing pheromones (usually large, non-volatile molecules), and transfer these pheromone molecules down the philtrum to the VNO via the nasopalatine ducts that travel through the incisive foramen of the hard palate. It also acts as a wind-direction detector: cold receptors in the skin of the rhinarium detect the orientation where evaporative cooling is highest, as determined by the wind direction.