Possum!
I found a dead opossum on the I-10 Dragoon Road exit ramp! (talking over 4500 feet in elevation)
As I was driving to the post office, I saw a dead animal and the color was obviously wrong for a skunk but it was too big to be a squirrel. Almost went on but curiosity got me so I went back to have a look and it was a freaking opossum! I didn't know we had them here, but I guess we do from reading a bit. I called Game and Fish but they haven't gotten back to me.
They seem cool and I now want one for a pet! 
too bad they don't live very long. there are some hilarious videos on You Tube.
= new reply since forum marked as read
"The highest elevation along I-10 occurs just east of Tucson, 20 miles (32 km) west of Willcox, at the mile marker 320 exit for the Amerind Foundation and Museum. The westbound lanes of I-10 briefly cross above 5,000 feet (1,500 m) above sea level." https://en.wikipedia.org/wiki/Interstate_10
that is actually exit 318, mile 320 is a little further east and is more like the rest area (and it is the highest elevation)
it is a weird area, it also is running almost north and south through here. 
Because they eat ticks, which carry the Borrella bacterium that causes the illness.
They have a low body temperature, so they don't incubate Rabies bacteria.
And, they're marsupials! 
