Any basal structure or part
base, bottom, minimum
Basic, elementary; relating to, or forming, the base, or point of origin.
In a phylogenetic tree, being a group, or member of a group, which diverged earlier. The earliest clade to branch in a larger clade.
Associated with the base of an organism or structure.
Of a minimal level that is necessary for maintaining the health or life of an organism.
The basis of something.
A stone laid during the construction of a (usually important) building, the laying of which is usually marked by a ceremony.