TXYZ, ARC (Tinker)
MDAnalysis can read Tinker xyz files .txyz and trajectory .arc files.
Differences between Tinker format and normal xyz files:
there is only one header line containing both the number of atoms and a comment
column 1 contains atom numbers (starting from 1)
column 6 contains atoms types
the following columns indicate connectivity (atoms to which that particular atom is bonded, according to numbering in column 1)