From my experience with babies u. geyri you can sex them at around 5-6 months (at least 40-45 grams) because the chest coloration in males starts slowly to appear.
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Lisabeth

2.3 Pogona vitticeps
2.2 Uromastyx geyri
3.2 Uromastyx ocellata
2.1 Uromastyx ornata
1.2 Laudakia stellio salehi