The order Rodentia is subdivided into two suborders, the Sciurognathi and the Hystricognathi. Within the Sciurognathi, the shortwavesensitive (SWS1) class of visual pigments is ultraviolet-sensitive (UVS) amongst the largely nocturnal murine species, whereas violet-sensitive (VS) pigments are thought to be present in diurnal ground and tree squirrels [1,2]. As the ancestral mammalian pigment is...
