I refer to Early Buddhism or Buddhism based on Samyutta/Samyukta discourses.
Cf.: Ven. Yinshun: Samyutta/Samyukta Buddhism
That is, Early Buddhism (unified Sangha) had two historical ages:
Samyutta/Samyukta Buddhism and Nikaya/Agama Buddhism (based on the principal four Nikayas/Agamas).
After Early Buddhism, there was the period of Sectarian Buddhism (Early Buddhist Schools) in India.