What is "abhidhammavatara"

Abhidhammavatara (Pali, also Abhidhammāvatāra), according to Encyclopædia Britannica is "the earliest effort at systematizing, in the form of a manual, the doctrines dealt with in the Abhidhamma (scholastic) section of the Theravada Buddhist canon. The Abhidhammavatara was written in Pali, apparently in the 5th century, by the poet and scholar Buddhadatta in the region of the Kaveri River, in southern India".

According to Rupert Gethin, the Abhidhammāvatāra (‘Introduction to Abhidharma’) was "written in the fifth century by Buddhadatta, a contemporary of Buddhaghosa."

Buddhadatta used this work to sum up and give original systematization to other commentaries dealing with Abhidhamma It is written in a chapter, verse format, with 24 chapters. The Abhidhammattha-sangaha has, in essence, superseded it.