Actually, my female Saharan is named Arthur. She doesn't seem to mind. 
I'm no sexing guru either, but from extended conversation (with illustrations!) with Doug Dix when I was trying to sex my Malis, your best bet is checking for hemipenal bulges. Not sure what age/size to tell you, though.
This picture is of my male Mali who is at least 3 years old, but looks female. Point your uro's nose away from you and lift the tail up over the back. You might see two raised ridges (on the tail side of the vent) with a dip in between like in the picture. If the ridges are parallel (like in the pic), you've likely got a male. If the ridges are at an angle like a "V", it's likely female (or too young to sex?) and those ridges are just tendons. If the area is smooth with no dip or ridges, it's also likely female.
Yours (as mentioned already) is probably too young to sex this way. Cute, though! I like the back markings.

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Torey
Eugene, Oregon, USA
1.1 Uromastyx geyri (Joe and Arthur)
3.0 Uromastyx dispar maliensis (Tank, Turtle, and Spike)
1.1 Uromastyx ornata (Scuttlebutt and Shazzbot)
2.1.2 Anolis carolinensis (Bowser, Sprocket, Leeloo, and Pickles 1&2)
1.1 Felis domesticus (Roscolux and Jenny)
