a cusp pattern seen in lower molars where the two buccal grooves (i.e., the groove between the protoconid and the hypoconid, and the groove between the hypoconid and the hypoconulid) form the arms of the "Y", and the lingual groove (i.e., the groove between the metaconid and the entoconid) forms the step of the "Y"; believed to be the primitive condition in hominins.
