  The content and distribution of cool interstellar medium (ISM, <30K) can
indicate the evolutionary mechanisms that transform late type to early type
galaxies (ETGs). To investigate this, ALMA observations of 12CO[2-1] line
emission were obtained for five dusty ETGs from a complete sample in
low-density environments. Four of the ETGs have massive (approximately 10^9
Msolar), extended molecular gas reservoirs with effective radii of
approximately 3 to 5 kpc. This work provides a kinematic and structural
analysis of these observations, to explore possible evolutionary mechanisms.
Axisymmetric or bisymmetric kinematic models were fitted to observations of
molecular gas discs, to quantify the dominant structures present and highlight
additional structures or asymmetries. Integral Field Unit (IFU) observations of
these ETGs were also examined where available. Two of the ETGs, GAMA64646 and
622305, appear to have undergone tidal disturbance leading to molecular gas
discs and/or star-forming inner rings. GAMA272990 may have undergone a merger,
leading to an elliptical galaxy with an embedded star-forming molecular gas
disc. GAMA622429 has probably undergone a minor merger, indicated by asymmetry
in molecular gas distribution and disturbance in optical images. The remaining
ETG, GAMA177186, was affected by source confusion from an offset source which
could be a high mass, dust- and gas- rich object at high redshift. Overall, it
appears that a high proportion of dusty ETGs in low-density environments have
massive, extended molecular gas reservoirs, and have undergone some kind of
interaction as part of their recent evolution. Secular evolution can then
(re-)transform the ETGs from star-forming to passive galaxies.
