As well as NM, there are a variety of W TX ranges that have produced at least one alterna from which there are no captive bred offspring available.

For example:
Eagle Mountains
Indio Mountains
Beach Mountains
Guadalupe Mountains

Actually, the list is quite long. To be honest, MOST mountain ranges in W TX are not represented in the captive population. W Sanderson and Iraan are common by that standard.
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Chris Harrison
San Antonio, Texas