Whatever this is, it's going to be VERY interesting. This little Geometrid caterpillar was found foraging on amargoso (a.k.a., Texas goat-bush, Castela erecta ssp. texana). Here's what I've learned:
(1) I can't find a match to this orange-dotted larva anywhere*;
(2) no Geometrids are listed in the World Lep Hostplants database as feeding on Castela or anything in the Simaroubaceae;
(3) this critter appears to be aposematically colored, i.e., it has warning coloration. That is usually an indicator of a toxic critter like Pipevine Swallowtail or Monarch larvae.

I should also mention that I think we saw several of these. Any help on ID would be appreciated.

* I found another photo of the same caterpillar from Laredo, Webb Co., identified only to family Geometridae. It also appears possibly to be on a Castela twig:
https://rolfnussbaumer.photoshelter.com/image/I0000M_LyKiRvaVk

Caterpillar - Needs ID

28 August 2016
Avondale Park
Denton, Denton County, Texas

This large caterpillar was about two inches long and had a girth of at least one-quarter inch if not more. While at first sight it looked indistinctively marked, a closer view of the pics showed that it actually possessed very distinctive markings on its body that made for excellent camouflage. But we have no clue what this likely moth caterpillar might be and it needs your ID. Thanks!