Evolutionarily incorrectly specified taxa due to ommission of legitimate members.
That is, a paraphyletic taxon is not a clade and this is because while all members share a , there also exist equivalent members that are excluded from the taxon.
Arguably the creation of paraphyletic taxa, or at least their retention, can be viewed as legitimate errors in taxonomy. Paraphyletic taxa, that is, can be legitimate deviations from the monophyletic ideal. Polyphyletic taxa, by contrast, are simply mistakes.
The classic example of a paraphyletic taxon is the which, at a minimum, excludes the birds (which are reptile descendants). A taxon that included the great apes but excluded also would be paraphyletic.