Complex sentence: Today it is common to define a "good taxon" as one that reflects evolutionary (phylogenetic) relationships, but this is not mandatory, as is evident from commonly used words for non-monophyletic entities such as invertebrates, conifers and fish.
Split into simpler sentences: Today it is common to define a "good taxon" as one that reflects evolutionary (phylogenetic) relationships. This is not mandatory, as is evident from commonly used words for non-monophyletic entities such as invertebrates, conifers and fish.