Must have been the rare arboreal ammonite. Some teuthologists believe this animal is related to the Cascadia tree octopus. The other option is that it was caught by a pterosaur that then dropped it into a coniferous forest, where it landed in sap and was caught fast.
Its called an Ambernite. That particular one is called Notrealatall philsfoolingus. I found about ten of them one day while dissecting a rare species of flying whale named Heliobalaena ceteovolus . I plan to jurassic park a whole bunch of these and make an army to cripple British shipping lanes for cutting off our tea supply... DANGNABBIT! The US isn't getting enough tea!
Also, there's the Tree Octopus, it might be related. Or it might be the lost link between cephs and humans!!! (The theory was termed as Notlinkedatall theory, which was published on the day Chrono said this.)
(Note: Chrono published it, it's on TONMO.com, somewhere.)