  Supernovae Type Iax (SNe Iax) are less energetic and less luminous than
typical thermonuclear explosions. A suggested explanation for the observed
characteristics of this subclass is a binary progenitor system consisting of a
CO white dwarf primary accreting from a helium star companion. A
single-degenerate explosion channel might be expected to result in a dense
circumstellar medium (CSM), although no evidence for such a CSM has yet been
observed for this subclass. Here we present recent Spitzer observations of the
SN Iax 2014dt obtained by the SPIRITS program nearly one year post-explosion
that reveal a strong mid-IR excess over the expected fluxes of more normal SNe
Ia. This excess is consistent with 1E-5 M_solar of newly formed dust, which
would be the first time that newly formed dust has been observed to form in a
normal Type Ia. The excess, however, is also consistent with a dusty CSM that
was likely formed in pre-explosion mass-loss, thereby suggesting a single
degenerate progenitor system. Compared to other SNe Ia that show significant
shock interaction (SNe Ia-CSM) and interacting core-collapse events (SNe IIn),
this dust shell in SN 2014dt is less massive. We consider the implications that
such a pre-existing dust shell has for the progenitor system, including a
binary system with a mass donor that is a red giant, a red supergiant, and an
asymptotic giant branch star.
