Our pre-maximum spectrum of SN 2009dc (and various comparison SNe) with a few major lines identified and days relative to maximum light indicated for each spectrum (in parentheses). From top to bottom, the SNe are the ‘standard overluminous’ Type Ia SN 1991T (Filippenko et al. 1992), a possible SC SN Ia SN 2004gu (Contreras et al. 2010, though this spectrum is from our own data base), another possible SC SN Ia SN 2006gz (Hicken et al. 2007) at two different epochs, SN 2009dc (this work), yet another possible SC SN Ia SN 2003fg (Howell et al. 2006), the SN 2002cx-like peculiar SN 2005hk (Chornock et al. 2006) and finally the ‘standard normal’ Type Ia SN 2005cf (Wang et al. 2009b). All spectra have had their host-galaxy recession velocities removed and have been dereddened according to the values presented in their respective references. Note that Si ii, S ii and O i are often found in near-maximum spectra of SNe Ia, but C ii is not.