Well that's funny... I sort of remembered the terrarium being labeled as "Heloderma suspectum", but now I'm not so sure... false memory? Or a mislabel maybe? (The park's signs leave a lot to be desired). Checking online, it does look more like a small beaded lizard (which is most likely considering it's a species native to the area). Random thought, anyone knows if H. horridum and H. suspectum can hybridize? I'm also seeing that there are like four or five species of Heloderma recognized- up until now I was aware of only the classic two...
I only know the classic two also. I revoke my "definitely", but it looks like a beaded lizard - not that I'm a professional herpetologist. Hopefully one of the herp guys here will chime in.