A recently reported bee fossil, of the genus "Melittosphex", is considered "an extinct lineage of pollen-collecting Apoidea, sister-group to the modern bees", and dates from the Lower Cretaceous (~100 mya). Features of its morphology place it clearly within the bees, but it retains two unmodified ancestral traits of the legs which betray its origin. The issue is still under debate, and the phylogenetic relationships among bee families are poorly understood.