Lincoln et al. (1) claim that Marine Group II Euryarchaeota (MG-II) are significant contributors to glycerol dibiphytanyl glycerol tetraether (GDGT) lipids in the ocean and biosynthesize crenarchaeol, a membrane lipid generally attributed to Thaumarchaeota (MG-I). The authors present two lines of convergent evidence for their far-reaching claim. The first line of evidence is the presence of GDGTs, including crenarchaeol, in suspended particulate matter (SPM) at 83 m, the archaeal community of which is nearly exclusively composed of MG-II (>94% of archaeal reads) (table 1 in ref. 1) as determined by pyrosequencing. However, according to Lincoln et al.’s definition, all SPM samples <100 m do … [↵][1]1To whom correspondence should be addressed. Email: stefan.schouten{at}nioz.nl. [1]: #xref-corresp-1-1