Three main groups of non-isoprenoid branched glycerol dialkyl glycerol tetraethers (brGDGTs) discussed in this study are (1) regular branched GDGTs (B-GDGTs), (2) derivatives with fewer methylated branches, called sparsely-branched GDGTs (SB-GDGTs), and (3) derivatives with a higher number of methylated branches, called overly-branched GDGTs (OB-GDGTs). Mass-to-charge (m/z) ratios for each molecule are labeled on the upper right. The numbers labeled in front of each molecule represent a varying number of methylated branches. For B-GDGTs, structures for C5-methylated (left column) and C6-methylated (right column) B-GDGTs are shown separately.