You can easily rear this to find out for sure. You could use a large fast food cup. Punch some drainage holes in the bottom, place some of the substrate as seen here in the bottom along with the pupa, insert upright stick, replace top with straw hole for aeration, and wait. Keep it in the same spot you found the pupa, since conditions (temperature/humidity) may need to be similar. Hopefully that's in your yard and not some spot where someone will discard it.

This looks like it's a sphinx moth pupae. The caterpillars are impressive critters, here is a picture of one. They usually burrow underground to pupae in about october, and emerge in the Spring. It will be interesting to see what comes out.