Who are you?! Help!

[Somerstamp]

Found this guy under a rock next to the Delaware river in New York State. It was about 3 inches in diameter after it balled up so it was big!
The iNat and Seek apps have no idea. Says it may be some sort of arthropod. I'm scouring my insect books...nothing.
Please help! I need to know what it is! It was so cool.

[livingplanet3]

It's what's known as a hellgramite, which is the larval form of a dobsonfly. The larvae are aquatic, while adult dobsonflies are winged -

https://mdc.mo.gov/discover-nature/fiel ... llgrammite

https://en.wikipedia.org/wiki/Dobsonfly

In New York, the local species of dobsonfly is Corydalus cornutus -

https://en.wikipedia.org/wiki/Corydalus_cornutus

[Somerstamp]

I had no idea that dobsonfly larva could be so big and not be totally submerged in water.
Awesome. Thank you!

[livingplanet3]

I had no idea that dobsonfly larva could be so big and not be totally submerged in water.
Awesome. Thank you!

If it was under a rock near the river, it was almost certainly preparing to metamorphose into an adult. They seek out some protected spot on land to go through this phase.