Lemur of mouse lemurs, the gray mouse lemur ("M. murinus"), golden-brown mouse lemur ("M. ravelobensis"), and Goodman's mouse lemur ("M. lehilahytsara") were considered the same species until recently, when genetic tests identified them as cryptic species. The lemur dentition is heterodont (having multiple tooth morphologies) and derives from an ancestral primate permanent dentition of . Indriids, sportive lemurs, the aye-aye, and the extinct sloth lemurs, monkey lemurs, and koala lemurs have reduced dentitions, having lost incisors, canines, or premolars. The ancestral deciduous dentition is , but young indriids, aye-ayes, koala lemurs, sloth lemurs, and probably monkey lemurs have fewer deciduous teeth.
I Should Have Known Better solo) and thus draws a line under a significant period of their early music. The song's middle sixteen section features George Harrison's brand new Rickenbacker 360/12 12-string guitar. The mono and stereo versions have slightly different harmonica introductions. In the stereo version, the harmonica drops out briefly. Also, a noticeably clumsy and audible tape edit is heard during the second chorus between "You're gonna say you love me too, oh," and "And when I ask you to be mine." In the UK, "I Should Have Known Better" appeared on "A Hard Day's Night" and was released on 10 July 1964.