As far as I know, Thanos killed half of a number of alien species before he got the six Infinity Stones and did the rest. The races include:
- Gamora's species
- Nebula's species
- The other children of Thanos's species
We know Thanos can exclude certain beings from the lottery (see this question).
Is there any evidence for whether these particular races were excluded from the snap, or did those races end up being cut in half again?