Why are Lamiaceae and Verbenaceae considered the two core families of Lamiales?

Lamiaceae and Verbenaceae are considered the core families of the Lamiales order primarily due to their significant size and shared morphological characteristics. Together, these two families comprise approximately 270 genera and over 8,300 species.1

Both families exhibit several defining structural traits:

• Vegetative and Floral Features: They possess opposite leaves, bilaterally symmetric flowers, and either two or four stamens.1
• Ovary Structure: They share a characteristic ovary composed of two carpels. Although each carpel initially contains two ovules, secondary partitions divide them into four chambers, each housing a single ovule or seed.1

While they share these fundamental traits, they are distinguished by the placement of the style—which arises from a central depression in Lamiaceae or the top of the ovary in Verbenaceae—and by their fruit types, which range from nutlets in mints to berries or drupes in the verbena family.1