Varieties grown in Central Asia, like Chinese and Japanese rice belong to a subspecies called JAPONICA, a group of short-mid grain cultivars.
South Asian rice, like ours, belongs to a subspecies called INDICA, and is mostly long grain. Length about 4 times as long as its width, per definition.
Chinese rice is shorter and rounder than our rice.
For our Thai heirloom black rice, add the subcultivar name to it and you get the full scientific name: ORYZA SATIVA INDICA SC. KHAO HOM NIL.